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Estevez-Fraga C, Altmann A, Parker CS, Scahill RI, Costa B, Chen Z, Manzoni C, Zarkali A, Durr A, Roos RAC, Landwehrmeyer B, Leavitt BR, Rees G, Tabrizi SJ, McColgan P. Genetic topography and cortical cell loss in Huntington's disease link development and neurodegeneration. Brain 2023; 146:4532-4546. [PMID: 37587097 PMCID: PMC10629790 DOI: 10.1093/brain/awad275] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2023] [Revised: 07/12/2023] [Accepted: 07/28/2023] [Indexed: 08/18/2023] Open
Abstract
Cortical cell loss is a core feature of Huntington's disease (HD), beginning many years before clinical motor diagnosis, during the premanifest stage. However, it is unclear how genetic topography relates to cortical cell loss. Here, we explore the biological processes and cell types underlying this relationship and validate these using cell-specific post-mortem data. Eighty premanifest participants on average 15 years from disease onset and 71 controls were included. Using volumetric and diffusion MRI we extracted HD-specific whole brain maps where lower grey matter volume and higher grey matter mean diffusivity, relative to controls, were used as proxies of cortical cell loss. These maps were combined with gene expression data from the Allen Human Brain Atlas (AHBA) to investigate the biological processes relating genetic topography and cortical cell loss. Cortical cell loss was positively correlated with the expression of developmental genes (i.e. higher expression correlated with greater atrophy and increased diffusivity) and negatively correlated with the expression of synaptic and metabolic genes that have been implicated in neurodegeneration. These findings were consistent for diffusion MRI and volumetric HD-specific brain maps. As wild-type huntingtin is known to play a role in neurodevelopment, we explored the association between wild-type huntingtin (HTT) expression and developmental gene expression across the AHBA. Co-expression network analyses in 134 human brains free of neurodegenerative disorders were also performed. HTT expression was correlated with the expression of genes involved in neurodevelopment while co-expression network analyses also revealed that HTT expression was associated with developmental biological processes. Expression weighted cell-type enrichment (EWCE) analyses were used to explore which specific cell types were associated with HD cortical cell loss and these associations were validated using cell specific single nucleus RNAseq (snRNAseq) data from post-mortem HD brains. The developmental transcriptomic profile of cortical cell loss in preHD was enriched in astrocytes and endothelial cells, while the neurodegenerative transcriptomic profile was enriched for neuronal and microglial cells. Astrocyte-specific genes differentially expressed in HD post-mortem brains relative to controls using snRNAseq were enriched in the developmental transcriptomic profile, while neuronal and microglial-specific genes were enriched in the neurodegenerative transcriptomic profile. Our findings suggest that cortical cell loss in preHD may arise from dual pathological processes, emerging as a consequence of neurodevelopmental changes, at the beginning of life, followed by neurodegeneration in adulthood, targeting areas with reduced expression of synaptic and metabolic genes. These events result in age-related cell death across multiple brain cell types.
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Affiliation(s)
- Carlos Estevez-Fraga
- Department of Neurodegenerative Disease, University College London, London WC1B 5EH, UK
| | - Andre Altmann
- Centre for Medical Image Computing, University College London, London WC1V 6LJ, UK
| | - Christopher S Parker
- Centre for Medical Image Computing, University College London, London WC1V 6LJ, UK
| | - Rachael I Scahill
- Department of Neurodegenerative Disease, University College London, London WC1B 5EH, UK
| | - Beatrice Costa
- Department of Neurodegenerative Disease, University College London, London WC1B 5EH, UK
- Gladstone Institutes, San Francisco, CA 94158, USA
| | - Zhongbo Chen
- Department of Neurodegenerative Disease, University College London, London WC1B 5EH, UK
| | - Claudia Manzoni
- School of Pharmacy, University College London, London WC1N 1AX, UK
| | - Angeliki Zarkali
- Dementia Research Centre, University College London, London WC1N 3AR, UK
| | - Alexandra Durr
- Sorbonne Université, Paris Brain Institute (ICM), AP-HP, Inserm, CNRS, Paris 75013, France
| | - Raymund A C Roos
- Department of Neurology, Leiden University Medical Centre, Leiden 2333, The Netherlands
| | | | - Blair R Leavitt
- Centre for Molecular Medicine and Therapeutics, Department of Medical Genetics, University of British Columbia, Vancouver BC V5Z 4H4Canada
- Division of Neurology, Department of Medicine, University of British Columbia Hospital, Vancouver BC V6T 2B5, Canada
| | - Geraint Rees
- Wellcome Centre for Human Neuroimaging, UCL Queen Square Institute of Neurology, University College London, London WC1N 3AR, UK
| | - Sarah J Tabrizi
- Department of Neurodegenerative Disease, University College London, London WC1B 5EH, UK
| | - Peter McColgan
- Department of Neurodegenerative Disease, University College London, London WC1B 5EH, UK
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Hannaway N, Zarkali A, Leyland LA, Bremner F, Nicholas JM, Wagner SK, Roig M, Keane PA, Toosy A, Chataway J, Weil RS. Visual dysfunction is a better predictor than retinal thickness for dementia in Parkinson's disease. J Neurol Neurosurg Psychiatry 2023; 94:742-750. [PMID: 37080759 PMCID: PMC10447370 DOI: 10.1136/jnnp-2023-331083] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/10/2023] [Accepted: 03/30/2023] [Indexed: 04/22/2023]
Abstract
BACKGROUND Dementia is a common and devastating symptom of Parkinson's disease (PD). Visual function and retinal structure are both emerging as potentially predictive for dementia in Parkinson's but lack longitudinal evidence. METHODS We prospectively examined higher order vision (skew tolerance and biological motion) and retinal thickness (spectral domain optical coherence tomography) in 100 people with PD and 29 controls, with longitudinal cognitive assessments at baseline, 18 months and 36 months. We examined whether visual and retinal baseline measures predicted longitudinal cognitive scores using linear mixed effects models and whether they predicted onset of dementia, death and frailty using time-to-outcome methods. RESULTS Patients with PD with poorer baseline visual performance scored lower on a composite cognitive score (β=0.178, SE=0.05, p=0.0005) and showed greater decreases in cognition over time (β=0.024, SE=0.001, p=0.013). Poorer visual performance also predicted greater probability of dementia (χ² (1)=5.2, p=0.022) and poor outcomes (χ² (1) =10.0, p=0.002). Baseline retinal thickness of the ganglion cell-inner plexiform layer did not predict cognitive scores or change in cognition with time in PD (β=-0.013, SE=0.080, p=0.87; β=0.024, SE=0.001, p=0.12). CONCLUSIONS In our deeply phenotyped longitudinal cohort, visual dysfunction predicted dementia and poor outcomes in PD. Conversely, retinal thickness had less power to predict dementia. This supports mechanistic models for Parkinson's dementia progression with onset in cortical structures and shows potential for visual tests to enable stratification for clinical trials.
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Affiliation(s)
- Naomi Hannaway
- Dementia Research Centre, Institute of Neurology, University College London, London, UK
| | - Angeliki Zarkali
- Dementia Research Centre, Institute of Neurology, University College London, London, UK
| | - Louise-Ann Leyland
- Dementia Research Centre, Institute of Neurology, University College London, London, UK
| | - Fion Bremner
- National Hospital for Neurology and Neurosurgery, University College London Hospitals, London, UK
| | - Jennifer M Nicholas
- Dementia Research Centre, Institute of Neurology, University College London, London, UK
- Department of Medical Statistics, London School of Hygiene and Tropical Medicine, London, UK
| | | | - Matthew Roig
- UCL Queen Square Institute of Neurology, London, UK
| | - Pearse A Keane
- UCL Queen Square Institute of Neurology, London, UK
- Institute of Ophthalmology, University College London, London, UK
| | - Ahmed Toosy
- Queen Square Multiple Sclerosis Centre, Department of Neuroinflammation, UCL Queen Square Institute of Neurology, University College London, London, UK
| | - Jeremy Chataway
- Queen Square Multiple Sclerosis Centre, Department of Neuroinflammation, UCL Queen Square Institute of Neurology, University College London, London, UK
- National Institute for Health Research, University College London Hospitals Biomedical Research Centre, London, UK
- MRC CTU at UCL, Institute of Clinical Trials and Methodology, University College London, London, UK
- Movement Disorders Centre, University College London, London, UK
| | - Rimona Sharon Weil
- Dementia Research Centre, Institute of Neurology, University College London, London, UK
- National Hospital for Neurology and Neurosurgery, University College London Hospitals, London, UK
- Movement Disorders Centre, University College London, London, UK
- The Wellcome Centre for Human Neuroimaging, Institute of Neurology, University College London, London, UK
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3
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Bhome R, Thomas GEC, Zarkali A, Weil RS. Structural and Functional Imaging Correlates of Visual Hallucinations in Parkinson's Disease. Curr Neurol Neurosci Rep 2023:10.1007/s11910-023-01267-1. [PMID: 37126201 DOI: 10.1007/s11910-023-01267-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 04/12/2023] [Indexed: 05/02/2023]
Abstract
PURPOSE OF REVIEW To review recent structural and functional MRI studies of visual hallucinations in Parkinson's disease. RECENT FINDINGS Previously, neuroimaging had shown inconsistent findings in patients with Parkinson's hallucinations, especially in studies examining grey matter volume. However, recent advances in structural and functional MRI techniques allow better estimates of structural connections, as well as the direction of connectivity in functional MRI. These provide more sensitive measures of changes in structural connectivity and allow models of the changes in directional functional connectivity to be tested. We identified 27 relevant studies and found that grey matter imaging continues to show heterogeneous findings in Parkinson's patients with visual hallucinations. Newer approaches in diffusion imaging and functional MRI are consistent with emerging models of Parkinson's hallucinations, suggesting shifts in attentional networks. In particular, reduced bottom-up, incoming sensory information, and over-weighting of top-down signals appear to be important drivers of visual hallucinations in Parkinson's disease.
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Affiliation(s)
- Rohan Bhome
- Dementia Research Centre, University College London, 8-11 Queen Square, London, WC1N 3AR, UK.
- Centre for Medical Image Computing, Department of Computer Science, University College London, London, UK.
| | | | - Angeliki Zarkali
- Dementia Research Centre, University College London, 8-11 Queen Square, London, WC1N 3AR, UK
| | - Rimona Sharon Weil
- Dementia Research Centre, University College London, 8-11 Queen Square, London, WC1N 3AR, UK
- Wellcome Centre for Human Neuroimaging, University College London, 12 Queen Square, London, WC1N 3AR, UK
- Movement Disorders Centre, National Hospital for Neurology and Neurosurgery, Queen Square, London, WC1N 3AR, UK
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4
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Edwards LJ, McColgan P, Helbling S, Zarkali A, Vaculčiaková L, Pine KJ, Dick F, Weiskopf N. Quantitative MRI maps of human neocortex explored using cell type-specific gene expression analysis. Cereb Cortex 2022; 33:5704-5716. [PMID: 36520483 PMCID: PMC10152104 DOI: 10.1093/cercor/bhac453] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2022] [Revised: 10/20/2022] [Accepted: 10/21/2022] [Indexed: 12/23/2022] Open
Abstract
Abstract
Quantitative magnetic resonance imaging (qMRI) allows extraction of reproducible and robust parameter maps. However, the connection to underlying biological substrates remains murky, especially in the complex, densely packed cortex. We investigated associations in human neocortex between qMRI parameters and neocortical cell types by comparing the spatial distribution of the qMRI parameters longitudinal relaxation rate (${R_{1}}$), effective transverse relaxation rate (${R_{2}}^{\ast }$), and magnetization transfer saturation (MTsat) to gene expression from the Allen Human Brain Atlas, then combining this with lists of genes enriched in specific cell types found in the human brain. As qMRI parameters are magnetic field strength-dependent, the analysis was performed on MRI data at 3T and 7T. All qMRI parameters significantly covaried with genes enriched in GABA- and glutamatergic neurons, i.e. they were associated with cytoarchitecture. The qMRI parameters also significantly covaried with the distribution of genes enriched in astrocytes (${R_{2}}^{\ast }$ at 3T, ${R_{1}}$ at 7T), endothelial cells (${R_{1}}$ and MTsat at 3T), microglia (${R_{1}}$ and MTsat at 3T, ${R_{1}}$ at 7T), and oligodendrocytes and oligodendrocyte precursor cells (${R_{1}}$ at 7T). These results advance the potential use of qMRI parameters as biomarkers for specific cell types.
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Affiliation(s)
- Luke J Edwards
- Department of Neurophysics, Max Planck Institute for Human Cognitive and Brain Sciences , Leipzig, DE, Germany
| | - Peter McColgan
- Department of Neurophysics, Max Planck Institute for Human Cognitive and Brain Sciences , Leipzig, DE, Germany
- Huntington’s Disease Centre, University College London , London, UK
| | - Saskia Helbling
- Department of Neurophysics, Max Planck Institute for Human Cognitive and Brain Sciences , Leipzig, DE, Germany
- Poeppel Lab, Ernst Strüngmann Institute (ESI) for Neuroscience in Cooperation with Max Planck Society , Frankfurt am Main, DE, Germany
| | - Angeliki Zarkali
- Dementia Research Centre, University College London , London, UK
| | - Lenka Vaculčiaková
- Department of Neurophysics, Max Planck Institute for Human Cognitive and Brain Sciences , Leipzig, DE, Germany
| | - Kerrin J Pine
- Department of Neurophysics, Max Planck Institute for Human Cognitive and Brain Sciences , Leipzig, DE, Germany
| | - Fred Dick
- Birkbeck/UCL Centre for Neuroimaging (BUCNI) , London, UK
| | - Nikolaus Weiskopf
- Department of Neurophysics, Max Planck Institute for Human Cognitive and Brain Sciences , Leipzig, DE, Germany
- Felix Bloch Institute for Solid State Physics, Faculty of Physics and Earth Sciences, Leipzig University , Leipzig, DE, Germany
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5
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Thomas GEC, Zeidman P, Sultana T, Zarkali A, Razi A, Weil RS. Changes in both top-down and bottom-up effective connectivity drive visual hallucinations in Parkinson's disease. Brain Commun 2022; 5:fcac329. [PMID: 36601626 PMCID: PMC9798302 DOI: 10.1093/braincomms/fcac329] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2022] [Revised: 10/13/2022] [Accepted: 12/12/2022] [Indexed: 12/15/2022] Open
Abstract
Visual hallucinations are common in Parkinson's disease and are associated with a poorer quality of life and a higher risk of dementia. An important and influential model that is widely accepted as an explanation for the mechanism of visual hallucinations in Parkinson's disease and other Lewy body diseases is that these arise due to aberrant hierarchical processing, with impaired bottom-up integration of sensory information and overweighting of top-down perceptual priors within the visual system. This hypothesis has been driven by behavioural data and supported indirectly by observations derived from regional activation and correlational measures using neuroimaging. However, until now, there was no evidence from neuroimaging for differences in causal influences between brain regions measured in patients with Parkinson's hallucinations. This is in part because previous resting-state studies focused on functional connectivity, which is inherently undirected in nature and cannot test hypotheses about the directionality of connectivity. Spectral dynamic causal modelling is a Bayesian framework that allows the inference of effective connectivity-defined as the directed (causal) influence that one region exerts on another region-from resting-state functional MRI data. In the current study, we utilize spectral dynamic causal modelling to estimate effective connectivity within the resting-state visual network in our cohort of 15 Parkinson's disease visual hallucinators and 75 Parkinson's disease non-visual hallucinators. We find that visual hallucinators display decreased bottom-up effective connectivity from the lateral geniculate nucleus to primary visual cortex and increased top-down effective connectivity from the left prefrontal cortex to primary visual cortex and the medial thalamus, as compared with non-visual hallucinators. Importantly, we find that the pattern of effective connectivity is predictive of the presence of visual hallucinations and associated with their severity within the hallucinating group. This is the first study to provide evidence, using resting-state effective connectivity, to support a model of aberrant hierarchical predictive processing as the mechanism for visual hallucinations in Parkinson's disease.
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Affiliation(s)
- George E C Thomas
- Dementia Research Centre, UCL Institute of Neurology, WC1N 3AR London, UK
| | - Peter Zeidman
- Wellcome Centre for Human Neuroimaging, UCL Institute of Neurology, WC1N 3AR London, UK
| | - Tajwar Sultana
- Department of Computer and Information Systems Engineering, NED University of Engineering & Technology, Karachi 75270, Pakistan
- Department of Biomedical Engineering, NED University of Engineering & Technology, Karachi 74800, Pakistan
- Neurocomputation Laboratory, NCAI Computer and Information Systems Department, NED University of Engineering and Technology, Karachi 75270, Pakistan
| | - Angeliki Zarkali
- Dementia Research Centre, UCL Institute of Neurology, WC1N 3AR London, UK
| | - Adeel Razi
- Wellcome Centre for Human Neuroimaging, UCL Institute of Neurology, WC1N 3AR London, UK
- Turner Institute for Brain and Mental Health, School of Psychological Sciences, Monash University, Clayton, VIC 3800, Australia
- CIFAR Azrieli Global Scholars Program, CIFAR, Toronto, ON M5G 1M1, Canada
| | - Rimona S Weil
- Dementia Research Centre, UCL Institute of Neurology, WC1N 3AR London, UK
- Wellcome Centre for Human Neuroimaging, UCL Institute of Neurology, WC1N 3AR London, UK
- Movement Disorders Consortium, UCL, London, UK
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6
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McColgan P, Gregory S, Zeun P, Zarkali A, Johnson EB, Parker C, Fayer K, Lowe J, Nair A, Estevez-Fraga C, Papoutsi M, Zhang H, Scahill RI, Tabrizi SJ, Rees G. Neurofilament light-associated connectivity in young-adult Huntington's disease is related to neuronal genes. Brain 2022; 145:3953-3967. [PMID: 35758263 PMCID: PMC9679168 DOI: 10.1093/brain/awac227] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2021] [Revised: 05/27/2022] [Accepted: 06/03/2022] [Indexed: 11/13/2022] Open
Abstract
Upregulation of functional network connectivity in the presence of structural degeneration is seen in the premanifest stages of Huntington's disease (preHD) 10-15 years from clinical diagnosis. However, whether widespread network connectivity changes are seen in gene carriers much further from onset has yet to be explored. We characterized functional network connectivity throughout the brain and related it to a measure of disease pathology burden (CSF neurofilament light, NfL) and measures of structural connectivity in asymptomatic gene carriers, on average 24 years from onset. We related these measurements to estimates of cortical and subcortical gene expression. We found no overall differences in functional (or structural) connectivity anywhere in the brain comparing control and preHD participants. However, increased functional connectivity, particularly between posterior cortical areas, correlated with increasing CSF NfL level in preHD participants. Using the Allen Human Brain Atlas and expression-weighted cell-type enrichment analysis, we demonstrated that this functional connectivity upregulation occurred in cortical regions associated with regional expression of genes specific to neuronal cells. This relationship was validated using single-nucleus RNAseq data from post-mortem Huntington's disease and control brains showing enrichment of neuronal-specific genes that are differentially expressed in Huntington's disease. Functional brain networks in asymptomatic preHD gene carriers very far from disease onset show evidence of upregulated connectivity correlating with increased disease burden. These changes occur among brain areas that show regional expression of genes specific to neuronal GABAergic and glutamatergic cells.
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Affiliation(s)
- Peter McColgan
- Huntington’s Disease Centre, Department of Neurodegenerative disease, UCL Queen Square Institute of Neurology, University College London, London WC1N 3BG, UK
| | - Sarah Gregory
- Huntington’s Disease Centre, Department of Neurodegenerative disease, UCL Queen Square Institute of Neurology, University College London, London WC1N 3BG, UK
| | - Paul Zeun
- Huntington’s Disease Centre, Department of Neurodegenerative disease, UCL Queen Square Institute of Neurology, University College London, London WC1N 3BG, UK
| | - Angeliki Zarkali
- Dementia Research Centre, University College London, London WC1N 3AR, UK
| | - Eileanoir B Johnson
- Huntington’s Disease Centre, Department of Neurodegenerative disease, UCL Queen Square Institute of Neurology, University College London, London WC1N 3BG, UK
| | - Christopher Parker
- Department of Computer Science and Centre for Medical Image Computing, University College London, London WC1V 6LJ, UK
| | - Kate Fayer
- Huntington’s Disease Centre, Department of Neurodegenerative disease, UCL Queen Square Institute of Neurology, University College London, London WC1N 3BG, UK
| | - Jessica Lowe
- Huntington’s Disease Centre, Department of Neurodegenerative disease, UCL Queen Square Institute of Neurology, University College London, London WC1N 3BG, UK
| | - Akshay Nair
- Huntington’s Disease Centre, Department of Neurodegenerative disease, UCL Queen Square Institute of Neurology, University College London, London WC1N 3BG, UK
- Max Planck University College London Centre for Computational Psychiatry and Ageing Research, UCL Queen Square Institute of Neurology, London WC1N 3BG, UK
| | - Carlos Estevez-Fraga
- Huntington’s Disease Centre, Department of Neurodegenerative disease, UCL Queen Square Institute of Neurology, University College London, London WC1N 3BG, UK
| | - Marina Papoutsi
- Huntington’s Disease Centre, Department of Neurodegenerative disease, UCL Queen Square Institute of Neurology, University College London, London WC1N 3BG, UK
| | - Hui Zhang
- Dementia Research Centre, University College London, London WC1N 3AR, UK
| | - Rachael I Scahill
- Huntington’s Disease Centre, Department of Neurodegenerative disease, UCL Queen Square Institute of Neurology, University College London, London WC1N 3BG, UK
| | - Sarah J Tabrizi
- Huntington’s Disease Centre, Department of Neurodegenerative disease, UCL Queen Square Institute of Neurology, University College London, London WC1N 3BG, UK
- Dementia Research Centre, University College London, London WC1N 3AR, UK
| | - Geraint Rees
- University College London Institute of Cognitive Neuroscience, University College London, London WC1N 3AZ, UK
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Zarkali A, Luppi AI, Stamatakis EA, Reeves S, McColgan P, Leyland LA, Lees AJ, Weil RS. Changes in dynamic transitions between integrated and segregated states underlie visual hallucinations in Parkinson's disease. Commun Biol 2022; 5:928. [PMID: 36075964 PMCID: PMC9458713 DOI: 10.1038/s42003-022-03903-x] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2022] [Accepted: 08/25/2022] [Indexed: 11/09/2022] Open
Abstract
Hallucinations are a core feature of psychosis and common in Parkinson’s. Their transient, unexpected nature suggests a change in dynamic brain states, but underlying causes are unknown. Here, we examine temporal dynamics and underlying structural connectivity in Parkinson’s-hallucinations using a combination of functional and structural MRI, network control theory, neurotransmitter density and genetic analyses. We show that Parkinson’s-hallucinators spent more time in a predominantly Segregated functional state with fewer between-state transitions. The transition from integrated-to-segregated state had lower energy cost in Parkinson’s-hallucinators; and was therefore potentially preferable. The regional energy needed for this transition was correlated with regional neurotransmitter density and gene expression for serotoninergic, GABAergic, noradrenergic and cholinergic, but not dopaminergic, receptors. We show how the combination of neurochemistry and brain structure jointly shape functional brain dynamics leading to hallucinations and highlight potential therapeutic targets by linking these changes to neurotransmitter systems involved in early sensory and complex visual processing. The examination of temporal dynamics in Parkinson’s-hallucinations reveals that the combination of neurochemistry and brain structure jointly shape functional brain dynamics leading to hallucinations.
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Affiliation(s)
- Angeliki Zarkali
- Dementia Research Centre, University College London, 8-11 Queen Square, London, WC1N 3AR, UK.
| | - Andrea I Luppi
- Division of Anaesthesia, School of Clinical Medicine, University of Cambridge, Cambridge, CB2 0QQ, UK.,Department of Clinical Neurosciences, University of Cambridge, Cambridge, CB2 0QQ, UK
| | - Emmanuel A Stamatakis
- Division of Anaesthesia, School of Clinical Medicine, University of Cambridge, Cambridge, CB2 0QQ, UK.,Department of Clinical Neurosciences, University of Cambridge, Cambridge, CB2 0QQ, UK
| | - Suzanne Reeves
- Division of Psychiatry, University College London, 149 Tottenham Court Rd, London, W1T 7BN, UK
| | - Peter McColgan
- Huntington's Disease Centre, University College London, Russell Square House, London, WC1B 5EH, UK
| | - Louise-Ann Leyland
- Dementia Research Centre, University College London, 8-11 Queen Square, London, WC1N 3AR, UK
| | - Andrew J Lees
- Reta Lila Weston Institute of Neurological Studies, University College London, 1 Wakefield Street, London, WC1N 1PJ, UK
| | - Rimona S Weil
- Dementia Research Centre, University College London, 8-11 Queen Square, London, WC1N 3AR, UK.,Wellcome Centre for Human Neuroimaging, University College London, 12 Queen Square, London, WC1N 3AR, UK.,Movement Disorders Consortium, University College London, London, WC1N 3BG, UK
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8
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Zarkali A, Weil RS. Using network approaches to unravel the mysteries of visual hallucinations in Lewy body dementia. Brain 2022; 145:1883-1885. [PMID: 35642563 DOI: 10.1093/brain/awac170] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2022] [Accepted: 04/26/2022] [Indexed: 11/14/2022] Open
Abstract
This scientific commentary refers to ‘Functional and structural brain network correlates of visual hallucinations in Lewy body dementia’ by Mehraram et al. (https://doi.org/10.1093/brain/awac094).
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Affiliation(s)
| | - Rimona S Weil
- Dementia Research Centre, UCL, London, UK.,Wellcome Centre for Human Neuroimaging, UCL, London, UK
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9
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Zarkali A, McColgan P, Leyland LA, Rees G, Weil RS. 128 White matter fibre loss in Parkinson’s disease hallucinations. J Neurol Neurosurg Psychiatry 2022. [DOI: 10.1136/jnnp-2022-abn.161] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Abstract
Visual hallucinations are common in Parkinson’s (PD) and associated with worse outcomes.1Neuroim- aging shows widespread but non-specific grey matter atrophy in PD-hallucinations1; white matter (WM) loss may be an earlier, more sensitive marker. To detect WM changes in PD-hallucinations we performed diffusion-weighted imaging in 105 patients with PD (n=86 without hallucinations [PD-non-VH], n=19 with hallucinations [PD-VH]), and 35 controls. We performed whole-brain fixel-based analysis,2a novel method that can identify micro- and macro-structural changes at fibre level and examined three measures:apparent fibre density (FD), sensitive to micro-structural changes,fibre bundle cross-section (FC), representing macro-structural changes,combined fibre density and cross-section (FDC).Groups did not differ in age or gender. PD-VH had higher total UPDRS score [63.5±35.6 vs 43.2±20.6 in PD-non-VH, (p=0.003)]; motor scores did not differ. We found macrostructural changes (FC reduction) within the splenium of the corpus callosum and left posterior thalamic radiation in PD/VH. Whilst there were no significant changes in FD, when using the combined FDC metric, we found large reductions within the splenium in PD-VH (>50% reduction compared to PD-non-VH).We demonstrate specific WM tract degeneration affecting posterior thalamic tracts in PD-hallucinations, providing direct mechanistic support for attentional models of visual hallucinations.ReferencesWeil,et al. Visual dysfunction in Parkinson’s disease.Brain2016 Jul 13.Raffelt,et al. Investigating white matter fibre density and morphology using fixel-based analysis.Neu- roimage2017;144:58–73.a.zarkali@ucl.ac.uk
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Kipps C, Kinton L, McCarron M, Nitkunan A, Petheram K, Ross-Russell A, Tripp A, Warner G, Zarkali A. Clinician burnout: results of an ABN survey of British neurologists. J Neurol Neurosurg Psychiatry 2022. [DOI: 10.1136/jnnp-2022-abn.32] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Abstract
Rising demand and increasing workload in the face of constrained resources are factors known to con- tribute to clinician burnout. Emotional exhaustion, depersonalisation and career dissatisfaction are some of the consequences. In the USA, neurologists are amongst the clinicians with the highest rates of burnout, but is this also a problem for British neurologists?Through the last quarter of 2019, the entire working membership of the ABN (neurologists and trainees) was surveyed using the well-validated Maslach Burnout Inventory. Other demographic and working practice data were also obtained. Of 1252 members, a total of 563 responses were obtained (45%).Over half the membership felt that neurologist burnout was an issue that the ABN should be involved with. Most respondents felt their work was meaningful and would choose neurology again as a specialty. Although job satisfaction overall was good, the majority felt that their schedule left insufficient family time. There were particular concerns regarding autonomy, the amount of administrative work and the lack of administrative support. A significant proportion of neurologists indicated that they had symptoms contributing to a sense of burnout once a week or more.Full results of the Maslach Burnout Inventory will be presented.ckipps@nhs.net
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Zarkali A, McColgan P, Ryten M, Reynolds R, Leyland LA, Lees AJ, Rees G, Weil RS. 129 Network controllability and regional gene expression explain visual hallucinations in Parkinson’s. J Neurol Neurosurg Psychiatry 2022. [DOI: 10.1136/jnnp-2022-abn.162] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/04/2022]
Abstract
Visual hallucinations are common in Parkinson’s (PD) and associated with poorer prognosis. Imaging studies have shown white matter and functional changes in PD-hallucinations1 2but the biological factors underlying selective vulnerability of brain regions are unknown.We performed diffusion-weighted imaging in 100 PD patients (81 without hallucinations [PD-non-VH], 19 with hallucinations [PD-VH]) and 34 controls. We used network-based statistics to identify structural con- nectivity changes in PD-VH and performed an analysis of controllability, an emerging technique that allows quantification of influence across the rest of the network. We used the Allen brain atlas to identify regional gene expression patterns associated with affected areas of the network.We identified a subnetwork of reduced connectivity in PD-VH. Within this network, PD-VH showed reduced controllability (influence over other brain regions), than PD-non-VH (U=526, p=0.014) and controls (U=176.5, p=0.003). This subnetwork appears to be critical for brain integration, as even in controls, nodes with high controllability were more likely to be within the subnetwork (U=572.5, p<0.001). Gene expression analysis revealed downregulated genes related to mRNA metabolism and upregulated genes related to membrane localisation.Our findings provide insights into how hallucinations are generated, with breakdown of a key structural subnetwork that exerts control across distributed brain regions.ReferenceShine,et al. The role of dysfunctional attentional control networks in visual misperceptions in Parkinson’s disease. HumBrainMapp;2014.a.zarkali@ucl.ac.uk
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Ross Russell AL, Zarkali A, Shribman S, Alexander SK, Warner TT, Jones M, Pereira A, Hughes TAT, Kipps C, Mummery CJ. 187 Variation in training: Results from a survey of UK neurology trainees. J Neurol Neurosurg Psychiatry 2022. [DOI: 10.1136/jnnp-2022-abn.216] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/04/2022]
Abstract
BackgroundNeurology training in the UK is governed by a national curriculum defining the outcomes every trainee must achieve. However, the delivery of neurology training and trainee satisfaction differs significantly across the UK1.The Association of British Neurologists Trainees (ABNT) recently completed a qualitative study of the highest and lowest performing trusts for neurology training across the UK and identified key indicators associated with trainee satisfaction2.AimTo establish the variation in these indicators across the country.MethodsWe conducted a survey of UK neurology trainees to audit regional performance against the indicators identified in the previous qualitative study.ResultsWe had responses from 50 trainees, covering all deaneries.There was consultant supervision reported >98% of the time. 56% of supervising consultants were on-site during working hours, and 66% were present during clinics. In 74% of cases, the supervising consultant for inpatient referrals also had pre-booked clinics.Adaptation of daily roles according to trainee level was only reported by 26% of trainees, with <20% reponses reporting variation in clinic lists, or examples of ST3 shadowing.52% of trainees were required to relocate during training.There was significant variation within deaneries, suggesting these factors are often determined at a trust level.1. Shribman S, Alexander SK, Zarkali A, et al. doi:10.1136/practneurol-2018–002129 amyrossrussell@gmail.com
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Zarkali A, McColgan P, Leyland LA, Lees A, Weil R. Visual dysfunction predicts cognitive impairment and white matter degenera- tion in Parkinson’s disease. J Neurol Neurosurg Psychiatry 2022. [DOI: 10.1136/jnnp-2022-abn.307] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/04/2022]
Abstract
IntroductionVisual dysfunction predicts Parkinson’s dementia but whether this translates to structural change is not known. We aimed to identify longitudinal white matter changes in Parkinson’s with low visual function and those who developed mild cognitive impairment(MCI).MethodsWe used fixel-based analysis to examine longitudinal white matter change in Parkinson’s. Diffusion MRI and clinical assessments were performed in 77 patients (22 low/55 high visual performers; and 13 MCI/51 normal cognition) and 25 controls at baseline and after 18 months. We compared micro-structural changes in fibre density, macro-structural changes in fibre cross-section and combined fibre density and cross-section across white matter, adjusting for age, gender and intracranial volume.ResultsParkinson’s with low visual performance showed worse cognition at follow-up (r=-0.386, p-0.024) and were more likely to develop MCI than those with normal vision (p=0.008). Parkinson’s with poor visual function showed diffuse micro-structural and macro-structural changes at baseline, whereas those with MCI showed fewer baseline changes. At follow-up, Parkinson’s with low visual function showed wide- spread macrostructural changes with up to 22% further reductions in fibre cross-section, involving the fronto-occipital fasciculi, external capsules, and middle cerebellar peduncles bilaterally. No longitudinal change was seen in baseline MCI or in MCI converters, even when combining the two groups.ConclusionsParkinson’s with poor visual function show increased white matter damage over time, providing further evidence for visual function as a marker of imminent cognitive decline.a.zarkali@ucl.ac.uk
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Ahmad H, Zarkali A, Kemp MJ, Banerjee G, Rees RN, Shribman S, Grote H, Ross Russell AL. 189 Association of British Neurology trainees: biennial national census. J Neurol Neurosurg Psychiatry 2022. [DOI: 10.1136/jnnp-2022-abn.218] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Abstract
BackgroundThe Association of British Neurology Trainees (ABNT) conducts a biennial census of neurology trainees.This acquires data on training, education, research, out of program experiences and trainees’ future plans, which are invaluable in shaping the future workforce. This is particularly important given the introduction and implementation of Shape of Training in 2022.AimTo review trainee perspectives on neurology specialist training in 2020.MethodsOnline questionnaire, designed by the ABNT committee, sent by email to all specialist neurology trainees and associate ABN members.ResultsResults will be reviewed and compared with previous data by members of the ABNT committee. We hope to present these results to an audience of aspiring neurologists, trainees and consultant neurologists.ConclusionThe results of this census, in combination with those conducted in 2015 and 2017, will influence Shape of Training discussions and new curriculum design. We hope the information it provides will facili- tate communication and collaboration between the ABN, Specialty Advisory Committee, Joint Royal College of Physicians Training Board and other external bodies. This will inform future workforce planning and guide the transition through curriculum reforms.hena.ahmad2@nhs.net
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Zarkali A, McColgan P, Leyland LA, Lees AJ, Weil RS. Longitudinal thalamic white and grey matter changes associated with visual hallucinations in Parkinson's disease. J Neurol Neurosurg Psychiatry 2022; 93:169-179. [PMID: 34583941 PMCID: PMC8785065 DOI: 10.1136/jnnp-2021-326630] [Citation(s) in RCA: 10] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/15/2021] [Accepted: 08/25/2021] [Indexed: 12/13/2022]
Abstract
OBJECTIVE Visual hallucinations are common in Parkinson's disease (PD) and associated with worse outcomes. Large-scale network imbalance is seen in PD-associated hallucinations, but mechanisms remain unclear. As the thalamus is critical in controlling cortical networks, structural thalamic changes could underlie network dysfunction in PD hallucinations. METHODS We used whole-brain fixel-based analysis and cortical thickness measures to examine longitudinal white and grey matter changes in 76 patients with PD (15 hallucinators, 61 non-hallucinators) and 26 controls at baseline, and after 18 months. We compared white matter and cortical thickness, adjusting for age, gender, time-between-scans and intracranial volume. To assess thalamic changes, we extracted volumes for 50 thalamic subnuclei (25 each hemisphere) and mean fibre cross-section (FC) for white matter tracts originating in each subnucleus and examined longitudinal change in PD-hallucinators versus non-hallucinators. RESULTS PD hallucinators showed white matter changes within the corpus callosum at baseline and extensive posterior tract involvement over time. Less extensive cortical thickness changes were only seen after follow-up. White matter connections from the right medial mediodorsal magnocellular thalamic nucleus showed reduced FC in PD hallucinators at baseline followed by volume reductions longitudinally. After follow-up, almost all thalamic subnuclei showed tract losses in PD hallucinators compared with non-hallucinators. INTERPRETATION PD hallucinators show white matter loss particularly in posterior connections and in thalamic nuclei, over time with relatively preserved cortical thickness. The right medial mediodorsal thalamic nucleus shows both connectivity and volume loss in PD hallucinations. Our findings provide mechanistic insights into the drivers of network imbalance in PD hallucinations and potential therapeutic targets.
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Affiliation(s)
| | - Peter McColgan
- Huntington's Disease Centre, UCL Institute of Neurology, London, UK
| | | | | | - Rimona Sharon Weil
- Dementia Research Centre, University College London, London, UK
- Wellcome Centre for Human Neuroimaging, University College London, London, UK
- Movement Disorders Consortium, National Hospital for Neurology and Neurosurgery, London, UK
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Bhome R, Zarkali A, Thomas GEC, Iglesias JE, Cole JH, Weil RS. Thalamic white matter macrostructure and subnuclei volumes in Parkinson's disease depression. NPJ Parkinsons Dis 2022; 8:2. [PMID: 35013327 PMCID: PMC8748828 DOI: 10.1038/s41531-021-00270-y] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2021] [Accepted: 12/20/2021] [Indexed: 12/04/2022] Open
Abstract
Depression is a common non-motor feature of Parkinson's disease (PD) which confers significant morbidity and is challenging to treat. The thalamus is a key component in the basal ganglia-thalamocortical network critical to the pathogenesis of PD and depression but the precise thalamic subnuclei involved in PD depression have not been identified. We performed structural and diffusion-weighted imaging (DWI) on 76 participants with PD to evaluate the relationship between PD depression and grey and white matter thalamic subnuclear changes. We used a thalamic segmentation method to divide the thalamus into its 50 constituent subnuclei (25 each hemisphere). Fixel-based analysis was used to calculate mean fibre cross-section (FC) for white matter tracts connected to each subnucleus. We assessed volume and FC at baseline and 14-20 months follow-up. A generalised linear mixed model was used to evaluate the relationship between depression, subnuclei volume and mean FC for each thalamic subnucleus. We found that depression scores in PD were associated with lower right pulvinar anterior (PuA) subnucleus volume. Antidepressant use was associated with higher right PuA volume suggesting a possible protective effect of treatment. After follow-up, depression scores were associated with reduced white matter tract macrostructure across almost all tracts connected to thalamic subnuclei. In conclusion, our work implicates the right PuA as a relevant neural structure in PD depression and future work should evaluate its potential as a therapeutic target for PD depression.
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Affiliation(s)
- R Bhome
- Dementia Research Centre, University College London, London, UK.
| | - A Zarkali
- Dementia Research Centre, University College London, London, UK
| | - G E C Thomas
- Dementia Research Centre, University College London, London, UK
| | - J E Iglesias
- Centre for Medical Image Computing, Department of Computer Science, University College London, London, UK
- Martinos Center for Biomedical Imaging, Massachusetts General Hospital and Harvard Medical School, Cambridge, USA
- Computer Science and Artificial Intelligence Laboratory, Massachusetts Institute of Technology, Cambridge, USA
| | - J H Cole
- Dementia Research Centre, University College London, London, UK
- Centre for Medical Image Computing, Department of Computer Science, University College London, London, UK
| | - R S Weil
- Dementia Research Centre, University College London, London, UK
- Wellcome Centre for Human Neuroimaging, University College London, London, UK
- Movement Disorders Consortium, National Hospital for Neurology and Neurosurgery, London, UK
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Wagen AZ, Zarkali A, Coath W, Buchanan SM, Keuss SE, Keshavan A, Lu K, James S, Pavisic IM, Street RE, Parker TD, Lane CA, Murray‐Smith H, Cash DM, Malone IB, Wong A, Richards M, Fox NC, Altmann A, Cole JH, Weil RS, Schott JM. Fixel‐based analysis of the effect of amyloid beta on white matter tracts in neurologically normal 70 year olds. Alzheimers Dement 2021. [DOI: 10.1002/alz.056187] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Affiliation(s)
- Aaron Z. Wagen
- Dementia Research Centre UCL Queen Square Institute of Neurology London United Kingdom
| | - Angeliki Zarkali
- Dementia Research Centre UCL Queen Square Institute of Neurology London United Kingdom
| | - William Coath
- Dementia Research Centre UCL Queen Square Institute of Neurology London United Kingdom
| | - Sarah M. Buchanan
- Dementia Research Centre UCL Queen Square Institute of Neurology London United Kingdom
| | - Sarah E. Keuss
- Dementia Research Centre UCL Queen Square Institute of Neurology London United Kingdom
| | - Ashvini Keshavan
- Dementia Research Centre UCL Queen Square Institute of Neurology London United Kingdom
| | - Kirsty Lu
- Dementia Research Centre UCL Queen Square Institute of Neurology London United Kingdom
| | - Sarah‐Naomi James
- MRC Unit for Lifelong Health and Ageing at UCL London United Kingdom
| | - Ivanna M. Pavisic
- Dementia Research Centre UCL Queen Square Institute of Neurology London United Kingdom
- Dementia Research Institute UCL London United Kingdom
| | - Rebecca E. Street
- Dementia Research Centre UCL Queen Square Institute of Neurology London United Kingdom
| | - Thomas D. Parker
- Dementia Research Centre UCL Queen Square Institute of Neurology London United Kingdom
| | - Christopher A. Lane
- Dementia Research Centre UCL Queen Square Institute of Neurology London United Kingdom
| | - Heidi Murray‐Smith
- Dementia Research Centre UCL Queen Square Institute of Neurology London United Kingdom
| | - David M. Cash
- Dementia Research Centre UCL Queen Square Institute of Neurology London United Kingdom
| | - Ian B. Malone
- Dementia Research Centre UCL Queen Square Institute of Neurology London United Kingdom
| | - Andrew Wong
- MRC Unit for Lifelong Health and Ageing at UCL London United Kingdom
| | - Marcus Richards
- MRC Unit for Lifelong Health and Ageing at UCL London United Kingdom
| | - Nick C. Fox
- Dementia Research Centre London United Kingdom
| | - Andre Altmann
- Centre for Medical Image Computing University College London London United Kingdom
| | - James H. Cole
- Dementia Research Centre UCL Queen Square Institute of Neurology London United Kingdom
- Centre of Medical Image Computing UCL Department of Medical Physics London United Kingdom
| | - Rimona S. Weil
- Dementia Research Centre UCL Queen Square Institute of Neurology London United Kingdom
| | - Jonathan M. Schott
- Dementia Research Centre UCL Queen Square Institute of Neurology London United Kingdom
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Thomas GEC, Zarkali A, Ryten M, Shmueli K, Gil-Martinez AL, Leyland LA, McColgan P, Acosta-Cabronero J, Lees AJ, Weil RS. Regional brain iron and gene expression provide insights into neurodegeneration in Parkinson's disease. Brain 2021; 144:1787-1798. [PMID: 33704443 PMCID: PMC8320305 DOI: 10.1093/brain/awab084] [Citation(s) in RCA: 32] [Impact Index Per Article: 10.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2020] [Revised: 11/20/2020] [Accepted: 12/14/2020] [Indexed: 12/11/2022] Open
Abstract
The mechanisms responsible for the selective vulnerability of specific neuronal populations in Parkinson's disease are poorly understood. Oxidative stress secondary to brain iron accumulation is one postulated mechanism. We measured iron deposition in 180 cortical regions of 96 patients with Parkinson's disease and 35 control subjects using quantitative susceptibility mapping. We estimated the expression of 15 745 genes in the same regions using transcriptomic data from the Allen Human Brain Atlas. Using partial least squares regression, we then identified the profile of gene transcription in the healthy brain that underlies increased cortical iron in patients with Parkinson's disease relative to controls. Applying gene ontological tools, we investigated the biological processes and cell types associated with this transcriptomic profile and identified the sets of genes with spatial expression profiles in control brains that correlated significantly with the spatial pattern of cortical iron deposition in Parkinson's disease. Gene ontological analyses revealed that these genes were enriched for biological processes relating to heavy metal detoxification, synaptic function and nervous system development and were predominantly expressed in astrocytes and glutamatergic neurons. Furthermore, we demonstrated that the genes differentially expressed in Parkinson's disease are associated with the pattern of cortical expression identified in this study. Our findings provide mechanistic insights into regional selective vulnerabilities in Parkinson's disease, particularly the processes involving iron accumulation.
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Affiliation(s)
| | | | - Mina Ryten
- Department of Neurodegenerative Disease, UCL Institute of Neurology, London, WC1B 5EH, UK
- NIHR Great Ormond Street Hospital Biomedical Research Centre, UCL, London, WC1N 1EH, UK
- Genetics and Genomic Medicine, Great Ormond Street Institute of Child Health, UCL, London, WC1N 1EH, UK
| | - Karin Shmueli
- Department of Medical Physics and Biomedical Engineering, Malet Place Engineering Building, UCL, London, WC1E 6BT, UK
| | - Ana Luisa Gil-Martinez
- Department of Neurodegenerative Disease, UCL Institute of Neurology, London, WC1B 5EH, UK
- Genetics and Genomic Medicine, Great Ormond Street Institute of Child Health, UCL, London, WC1N 1EH, UK
| | | | - Peter McColgan
- Huntington’s Disease Centre, UCL Institute of Neurology, London, WC1B 5EH, UK
| | | | - Andrew J Lees
- Reta Lila Weston Institute of Neurological Studies, London, WC1N 1PJ, UK
| | - Rimona S Weil
- Dementia Research Centre, UCL, London, WC1N 3AR, UK
- Wellcome Centre for Human Neuroimaging, UCL, London, WC1N 3AR, UK
- Movement Disorders Consortium, UCL, London, WC1N 3BG, UK
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Zarkali A, Weil RS. Beyond dopamine: Further evidence of cholinergic dysfunction in Parkinson's disease (Commentary on Keo et al., 2021). Eur J Neurosci 2021; 53:3740-3742. [PMID: 33960522 DOI: 10.1111/ejn.15269] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2021] [Revised: 04/13/2021] [Accepted: 04/29/2021] [Indexed: 11/30/2022]
Affiliation(s)
| | - Rimona S Weil
- Dementia Research Centre, University College London, London, UK.,Wellcome Centre for Human Neuroimaging, University College London, London, UK.,Movement Disorders Consortium, National Hospital for Neurology and Neurosurgery, London, UK
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Zarkali A, McColgan P, Leyland L, Lees AJ, Weil RS. Visual Dysfunction Predicts Cognitive Impairment and White Matter Degeneration in Parkinson's Disease. Mov Disord 2021; 36:1191-1202. [PMID: 33421201 PMCID: PMC8248368 DOI: 10.1002/mds.28477] [Citation(s) in RCA: 26] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2020] [Revised: 11/23/2020] [Accepted: 12/14/2020] [Indexed: 12/13/2022] Open
Abstract
BACKGROUND Visual dysfunction predicts dementia in Parkinson's disease (PD), but whether this translates to structural change is not known. The objectives of this study were to identify longitudinal white matter changes in patients with Parkinson's disease and low visual function and also in those who developed mild cognitive impairment. METHODS We used fixel-based analysis to examine longitudinal white matter change in PD. Diffusion MRI and clinical assessments were performed in 77 patients at baseline (22 low visual function/55 intact vision and 13 PD-mild cognitive impairment/51 normal cognition) and 25 controls and again after 18 months. We compared microstructural changes in fiber density, macrostructural changes in fiber bundle cross-section and combined fiber density and cross-section, across white matter, adjusting for age, sex, and intracranial volume. RESULTS Patients with PD and visual dysfunction showed worse cognitive performance at follow-up and were more likely to develop mild cognitive impairment compared with those with normal vision (P = 0.008). Parkinson's with poor visual function showed diffuse microstructural and macrostructural changes at baseline, whereas those with mild cognitive impairment showed fewer baseline changes. At follow-up, Parkinson's with low visual function showed widespread macrostructural changes, involving the fronto-occipital fasciculi, external capsules, and middle cerebellar peduncles bilaterally. No longitudinal change was seen in those with mild cognitive impairment at baseline or converters, even when the 2 groups were combined. CONCLUSION Parkinson's patients with poor visual function show increased white matter damage over time, providing further evidence for visual function as a marker of imminent cognitive decline. © 2021 The Authors. Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Society.
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Affiliation(s)
- Angeliki Zarkali
- Dementia Research CentreUniversity College LondonLondonUnited Kingdom
| | - Peter McColgan
- Huntington's Disease CentreUniversity College LondonLondonUnited Kingdom
| | | | - Andrew J. Lees
- Reta Lila Weston Institute of Neurological StudiesLondonUnited Kingdom
| | - Rimona S. Weil
- Dementia Research CentreUniversity College LondonLondonUnited Kingdom,Wellcome Centre for Human NeuroimagingUniversity College LondonLondonUnited Kingdom,Movement Disorders ConsortiumNational Hospital for Neurology and NeurosurgeryLondonUnited Kingdom
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Zarkali A, McColgan P, Leyland LA, Lees AJ, Rees G, Weil RS. Organisational and neuromodulatory underpinnings of structural-functional connectivity decoupling in patients with Parkinson's disease. Commun Biol 2021; 4:86. [PMID: 33469150 PMCID: PMC7815846 DOI: 10.1038/s42003-020-01622-9] [Citation(s) in RCA: 28] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2020] [Accepted: 12/18/2020] [Indexed: 01/01/2023] Open
Abstract
Parkinson's dementia is characterised by changes in perception and thought, and preceded by visual dysfunction, making this a useful surrogate for dementia risk. Structural and functional connectivity changes are seen in humans with Parkinson's disease, but the organisational principles are not known. We used resting-state fMRI and diffusion-weighted imaging to examine changes in structural-functional connectivity coupling in patients with Parkinson's disease, and those at risk of dementia. We identified two organisational gradients to structural-functional connectivity decoupling: anterior-to-posterior and unimodal-to-transmodal, with stronger structural-functional connectivity coupling in anterior, unimodal areas and weakened towards posterior, transmodal regions. Next, we related spatial patterns of decoupling to expression of neurotransmitter receptors. We found that dopaminergic and serotonergic transmission relates to decoupling in Parkinson's overall, but instead, serotonergic, cholinergic and noradrenergic transmission relates to decoupling in patients with visual dysfunction. Our findings provide a framework to explain the specific disorders of consciousness in Parkinson's dementia, and the neurotransmitter systems that underlie these.
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Affiliation(s)
- Angeliki Zarkali
- Dementia Research Centre, University College London, 8-11 Queen Square, London, WC1N 3AR, UK.
| | - Peter McColgan
- Huntington's Disease Centre, University College London, Russell Square House, London, WC1B 5EH, UK
| | - Louise-Ann Leyland
- Dementia Research Centre, University College London, 8-11 Queen Square, London, WC1N 3AR, UK
| | - Andrew J Lees
- Reta Lila Weston Institute of Neurological Studies, 1 Wakefield Street, London, WC1N 1PJ, UK
| | - Geraint Rees
- Institute of Cognitive Neuroscience, University College London, 17-19 Queen Square, London, WC1N 3AR, UK
- Wellcome Centre for Human Neuroimaging, University College London, 12 Queen Square, London, WC1N 3AR, UK
| | - Rimona S Weil
- Dementia Research Centre, University College London, 8-11 Queen Square, London, WC1N 3AR, UK
- Wellcome Centre for Human Neuroimaging, University College London, 12 Queen Square, London, WC1N 3AR, UK
- Movement Disorders Consortium, University College London, London, WC1N 3BG, UK
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Zarkali A, McColgan P, Ryten M, Reynolds R, Leyland LA, Lees AJ, Rees G, Weil RS. Differences in network controllability and regional gene expression underlie hallucinations in Parkinson's disease. Brain 2020; 143:3435-3448. [PMID: 33118028 PMCID: PMC7719028 DOI: 10.1093/brain/awaa270] [Citation(s) in RCA: 25] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2019] [Revised: 06/29/2020] [Accepted: 07/02/2020] [Indexed: 12/19/2022] Open
Abstract
Visual hallucinations are common in Parkinson's disease and are associated with poorer prognosis. Imaging studies show white matter loss and functional connectivity changes with Parkinson's visual hallucinations, but the biological factors underlying selective vulnerability of affected parts of the brain network are unknown. Recent models for Parkinson's disease hallucinations suggest they arise due to a shift in the relative effects of different networks. Understanding how structural connectivity affects the interplay between networks will provide important mechanistic insights. To address this, we investigated the structural connectivity changes that accompany visual hallucinations in Parkinson's disease and the organizational and gene expression characteristics of the preferentially affected areas of the network. We performed diffusion-weighted imaging in 100 patients with Parkinson's disease (81 without hallucinations, 19 with visual hallucinations) and 34 healthy age-matched controls. We used network-based statistics to identify changes in structural connectivity in Parkinson's disease patients with hallucinations and performed an analysis of controllability, an emerging technique that allows quantification of the influence a brain region has across the rest of the network. Using these techniques, we identified a subnetwork of reduced connectivity in Parkinson's disease hallucinations. We then used the Allen Institute for Brain Sciences human transcriptome atlas to identify regional gene expression patterns associated with affected areas of the network. Within this network, Parkinson's disease patients with hallucinations showed reduced controllability (less influence over other brain regions), than Parkinson's disease patients without hallucinations and controls. This subnetwork appears to be critical for overall brain integration, as even in controls, nodes with high controllability were more likely to be within the subnetwork. Gene expression analysis of gene modules related to the affected subnetwork revealed that down-weighted genes were most significantly enriched in genes related to mRNA and chromosome metabolic processes (with enrichment in oligodendrocytes) and upweighted genes to protein localization (with enrichment in neuronal cells). Our findings provide insights into how hallucinations are generated, with breakdown of a key structural subnetwork that exerts control across distributed brain regions. Expression of genes related to mRNA metabolism and membrane localization may be implicated, providing potential therapeutic targets.
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Affiliation(s)
- Angeliki Zarkali
- Dementia Research Centre, University College London, 8-11 Queen Square, London, WC1N 3AR, UK
| | - Peter McColgan
- Huntington’s Disease Centre, University College London, Russell Square House, London, WC1B 5EH, UK
| | - Mina Ryten
- Department of Neurodegenerative Disease, UCL Institute of Neurology, 10-12 Russell Square House, London, UK
| | - Regina Reynolds
- Department of Neurodegenerative Disease, UCL Institute of Neurology, 10-12 Russell Square House, London, UK
| | - Louise-Ann Leyland
- Dementia Research Centre, University College London, 8-11 Queen Square, London, WC1N 3AR, UK
| | - Andrew J Lees
- Reta Lila Weston Institute of Neurological Studies, 1 Wakefield Street, London, WC1N 1PJ, UK
| | - Geraint Rees
- Institute of Cognitive Neuroscience, University College London, 17-19 Queen Square, London, WC1N 3AR, UK
- Wellcome Centre for Human Neuroimaging, University College London, 12 Queen Square, London, WC1N 3AR, UK
| | - Rimona S Weil
- Dementia Research Centre, University College London, 8-11 Queen Square, London, WC1N 3AR, UK
- Wellcome Centre for Human Neuroimaging, University College London, 12 Queen Square, London, WC1N 3AR, UK
- Movement Disorders Consortium, University College London, London WC1N 3BG, UK
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23
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Zarkali A, McColgan P, Ryten M, Reynolds RH, Leyland LA, Lees AJ, Rees G, Weil RS. Dementia risk in Parkinson's disease is associated with interhemispheric connectivity loss and determined by regional gene expression. Neuroimage Clin 2020; 28:102470. [PMID: 33395965 PMCID: PMC7581968 DOI: 10.1016/j.nicl.2020.102470] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2020] [Revised: 09/08/2020] [Accepted: 10/11/2020] [Indexed: 12/11/2022]
Abstract
Parkinson's dementia is a common and devastating part of Parkinson's disease. Whilst timing and severity vary, dementia in Parkinson's is often preceded by visual dysfunction. White matter changes, representing axonal loss, occur early in the disease process. Clarifying which white matter connections are affected in Parkinson's with visual dysfunction and why specific connections are vulnerable will provide important mechanistic insights. Here, we use diffusion tractography in 100 Parkinson's patients (33 low visual performers) and 34 controls to identify patterns of connectivity loss in Parkinson's with visual dysfunction. We examine the relationship between regional transcription and connectivity loss, using the Allen Institute for Brain Science transcriptome atlas. We show that interhemispheric connections are preferentially affected in Parkinson's low visual performers. Interhemispheric connection loss was associated with downweighted genes related to the smoothened signalling pathway (enriched in glutamatergic neurons) and upweighted metabolic genes. Risk genes for Parkinson's but not Alzheimer's or Dementia with Lewy bodies were over-represented in upweighted genes associated with interhemispheric connection loss. Our findings suggest selective vulnerability in Parkinson's patients at highest risk of dementia (those with visual dysfunction), where differences in gene expression and metabolic dysfunction, affecting longer connections with higher metabolic burden, drive connectivity loss.
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Affiliation(s)
- Angeliki Zarkali
- Dementia Research Centre, University College London, 8-11 Queen Square, London WC1N 3AR, UK.
| | - Peter McColgan
- Huntington's Disease Centre, University College London, Russell Square House, London WC1B 5EH, UK
| | - Mina Ryten
- NIHR Great Ormond Street Hospital Biomedical Research Centre, University College London, London, UK; Great Ormond Street Institute of Child Health, Genetics and Genomic Medicine, University College London, London, UK; Department of Neurodegenerative Disease, UCL Institute of Neurology, 10-12 Russell Square House, London WC1B 5EH, UK
| | - Regina H Reynolds
- NIHR Great Ormond Street Hospital Biomedical Research Centre, University College London, London, UK; Great Ormond Street Institute of Child Health, Genetics and Genomic Medicine, University College London, London, UK; Department of Neurodegenerative Disease, UCL Institute of Neurology, 10-12 Russell Square House, London WC1B 5EH, UK
| | - Louise-Ann Leyland
- Dementia Research Centre, University College London, 8-11 Queen Square, London WC1N 3AR, UK
| | - Andrew J Lees
- Reta Lila Weston Institute of Neurological Studies, 1 Wakefield Street, London WC1N 1PJ, UK
| | - Geraint Rees
- Institute of Cognitive Neuroscience, University College London, 17-19 Queen Square, London WC1N 3AR, UK; Wellcome Centre for Human Neuroimaging, University College London, 12 Queen Square, London WC1N 3AR, UK
| | - Rimona S Weil
- Dementia Research Centre, University College London, 8-11 Queen Square, London WC1N 3AR, UK; Wellcome Centre for Human Neuroimaging, University College London, 12 Queen Square, London WC1N 3AR, UK; Movement Disorders Consortium, University College London, London WC1N 3BG, UK
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24
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Foley JA, Dore C, Zarkali A, Livingston G, Cipolotti L, Mummery CJ, Weil RS. Evaluation of START (STrAtegies for RelaTives) adapted for carers of people with Lewy body dementia. Future Healthc J 2020; 7:e27-e29. [PMID: 33094242 PMCID: PMC7571743 DOI: 10.7861/fhj.2020-0003] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Family carers of people with Lewy body dementia (LBD) have a particularly high burden of care, as LBD has a faster rate of decline, greater physical dependence and additional neuropsychiatric disturbances compared with other dementias. Despite this, there are no evidence-based support services designed specifically for LBD carers. STrAtegies for RelaTives (START) is an eight-session, individually delivered coping therapy that has been shown in a randomised controlled trial to reduce depression and anxiety symptoms and increase quality of life in carers of people with dementia, with effects lasting several years. We adapted START for LBD, and piloted its use both face-to-face and on the phone with 10 carers to test acceptability and indications of similar effects in this group. Our findings suggest that the therapy was acceptable and feasible using either delivery mode, providing much appreciated and needed strategies, education and support for carers of people with LBD. Trials of effectiveness are now needed.
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Affiliation(s)
- Jennifer A Foley
- ANational Hospital for Neurology and Neurosurgery, London, UK and University College London Institute of Neurology, London, UK,Address for correspondence: Dr Jennifer A Foley, Department of Neuropsychology, Box 37, National Hospital for Neurology and Neurosurgery, Queen Square, London WC1N 3BG, UK.
| | - Charlotte Dore
- BNational Hospital for Neurology and Neurosurgery, London, UK
| | | | - Gill Livingston
- DUniversity College London, London, UK and Camden and Islington NHS Foundation Trust, London, UK
| | - Lisa Cipolotti
- ENational Hospital for Neurology and Neurosurgery, London, UK
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25
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Abstract
Visual hallucinations are a common and often distressing feature of Parkinson's disease; they are ephemeral and capricious, making them difficult to study but tend to be more prominent in dim illumination. Flickering stimuli can induce simple hallucinations even in healthy individuals. We tested a stroboscope and an equivalent full-screen flickering stimulus in 16 participants: 7 patients with Parkinson's and habitual visual hallucinations, 6 Parkinson's patients without hallucinations and 3 controls. Both flicker sources induced varied geometrical hallucinations in 4 participants (25%) and complex hallucinations in 1 but neither induced typical Parkinson's-associated hallucinations.
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Affiliation(s)
- Angeliki Zarkali
- Dementia Research Centre, University College London, London, UK,Correspondence to: Angeliki Zarkali, Dementia Research Centre, University College London, 8-11 Queen Square,
London, WC1N 3AR, UK. Tel.: +44 07833157065; E-mail:
| | - Andrew J. Lees
- Reta Lila Weston Institute, University College London, London, UK
| | - Rimona S. Weil
- Dementia Research Centre, University College London, London, UK,Wellcome Centre for Human Neuroimaging, University College London, London, UK
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26
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Zarkali A, McColgan P, Leyland LA, Lees AJ, Rees G, Weil RS. Fiber-specific white matter reductions in Parkinson hallucinations and visual dysfunction. Neurology 2020; 94:e1525-e1538. [PMID: 32094242 PMCID: PMC7251523 DOI: 10.1212/wnl.0000000000009014] [Citation(s) in RCA: 37] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2019] [Accepted: 10/11/2019] [Indexed: 12/13/2022] Open
Abstract
OBJECTIVE To investigate the microstructural and macrostructural white matter changes that accompany visual hallucinations and low visual performance in Parkinson disease, a risk factor for Parkinson dementia. METHODS We performed fixel-based analysis, a novel technique that provides metrics of specific fiber-bundle populations within a voxel (or fixel). Diffusion MRI data were acquired from patients with Parkinson disease (n = 105, of whom 34 were low visual performers and 19 were hallucinators) and age-matched controls (n = 35). We used whole-brain fixel-based analysis to compare microstructural differences in fiber density (FD), macrostructural differences in fiber bundle cross section (FC), and the combined FD and FC (FDC) metric across all white matter fixels. We then performed a tract-of-interest analysis comparing the most sensitive FDC metric across 11 tracts within the visual system. RESULTS Patients with Parkinson disease hallucinations exhibited macrostructural changes (reduced FC) within the splenium of the corpus callosum and the left posterior thalamic radiation compared to patients without hallucinations. While there were no significant changes in FD, we found large reductions in the combined FDC metric in Parkinson hallucinators within the splenium (>50% reduction compared to nonhallucinators). Patients with Parkinson disease and low visual performance showed widespread microstructural and macrostructural changes within the genu and splenium of the corpus callosum, bilateral posterior thalamic radiations, and left inferior fronto-occipital fasciculus. CONCLUSIONS We demonstrate specific white matter tract degeneration affecting posterior thalamic tracts in patients with Parkinson disease with hallucinations and low visual performance, providing direct mechanistic support for attentional models of visual hallucinations.
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Affiliation(s)
- Angeliki Zarkali
- From the Dementia Research Centre (A.Z., L.-A.L., R.S.W.), Huntington's Disease Centre (P.M.), Institute of Cognitive Neuroscience (G.R.), and Wellcome Centre for Human Neuroimaging (G.R., R.S.W.), University College London; and Reta Lila Weston Institute of Neurological Studies (A.J.L.), London, UK.
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27
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Zarkali A, Adams RA, Psarras S, Leyland LA, Rees G, Weil RS. Increased weighting on prior knowledge in Lewy body-associated visual hallucinations. Brain Commun 2019; 1:fcz007. [PMID: 31886459 PMCID: PMC6924538 DOI: 10.1093/braincomms/fcz007] [Citation(s) in RCA: 34] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2019] [Revised: 06/03/2019] [Accepted: 07/26/2019] [Indexed: 01/25/2023] Open
Abstract
Hallucinations are a common and distressing feature of many psychiatric and neurodegenerative conditions. In Lewy body disease, visual hallucinations are a defining feature, associated with worse outcomes; yet their mechanisms remain unclear and treatment options are limited. Here, we show that hallucinations in Lewy body disease are associated with altered integration of top-down predictions with incoming sensory evidence, specifically with an increased relative weighting of prior knowledge. We tested 37 individuals with Lewy body disease, 17 habitual hallucinators and 20 without hallucinations, and 20 age-matched healthy individuals. We employed an image-based learning paradigm to test whether people with Lewy body disease and visual hallucinations show higher dependence on prior knowledge. We used two-tone images that are difficult to disambiguate without any prior information but generate a strong percept when information is provided. We measured discrimination sensitivity before and after this information was provided. We observed that in people with Lewy body disease who experience hallucinations, there was greater improvement in discrimination sensitivity after information was provided, compared to non-hallucinators and controls. This suggests that people with Lewy body disease and hallucinations place higher relative weighting on prior knowledge than those who do not hallucinate. Importantly, increased severity of visual hallucinations was associated with an increased effect of prior knowledge. Together these findings suggest that visual hallucinations in Lewy body disease are linked to a shift towards top-down influences on perception and away from sensory evidence, perhaps due to an increase in sensory noise. This provides important mechanistic insights to how hallucinations develop in Lewy body disease, with potential for revealing new therapeutic targets.
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Affiliation(s)
- Angeliki Zarkali
- Dementia Research Centre, University College London, 8-11 Queen Square, London WC1N 3AR, UK,Correspondence to: Angeliki Zarkali Dementia Research Centre, University College London, 8-11 Queen Square, London WC1N 3AR, UK E-mail:
| | - Rick A Adams
- Max Planck Centre for Computational Psychiatry and Aging Research, University College London, 10-12 Russell Square, London WC1B 5EH, UK,Department of Computer Science, University College London, Gower Street, London WC1E 6BT, UK
| | - Stamatios Psarras
- Space Syntax Laboratory, University College London, 14 Upper Woburn Place, London WC1H 0NN, UK
| | - Louise-Ann Leyland
- Dementia Research Centre, University College London, 8-11 Queen Square, London WC1N 3AR, UK
| | - Geraint Rees
- Institute of Cognitive Neuroscience, University College London, 17-19 Queen Square, London WC1N 3AR, UK,Welcome Centre for Human Neuroimaging, University College London, 12 Queen Square, London WC1N 3AR, UK
| | - Rimona S Weil
- Dementia Research Centre, University College London, 8-11 Queen Square, London WC1N 3AR, UK,Welcome Centre for Human Neuroimaging, University College London, 12 Queen Square, London WC1N 3AR, UK
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28
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Cheng SF, Zarkali A, Richards T, Simister R, Chandratheva A. Carotid artery stenosis, an underestimated cause of stroke recurrence in patients with ischaemic monocular visual loss. Ann R Coll Surg Engl 2019; 101:579-583. [PMID: 31155910 DOI: 10.1308/rcsann.2019.0071] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
INTRODUCTION Isolated monocular ischaemic events are thought to be low risk for stroke recurrence. In the presence of carotid stenosis however, the risks should not be treated similarly and surgical intervention should be considered at an early stage. The aim of this study was to determine the vascular risk profile and stroke recurrence in patients with ischaemic monocular visual loss. METHODS AND METHODS Consecutive records for all patients with monocular ischaemia were reviewed from January 2014 to October 2016. Stroke, transient ischaemic attack or monocular ischaemia recurrence within 90 days were recorded. Carotid stenosis was assessed with duplex ultrasound, computed tomography or magnetic resonance angiography. RESULTS In total, 400 patients presented with monocular ischaemia; 391 had carotid imaging (97.8%). Causality was symptomatic carotid stenosis ≥ 50% in 53 (13.6%), including carotid stenosis ≥ 70% in 31 (7.9%). Patients with permanent visual loss (n = 131) were more likely to have significant stenosis compared with patients with transient visual loss (n = 260), 19.8% compared with 10.4% (P = 0.012). Recurrent stroke, transient ischaemic attack or monocular ischaemia within 90 days after presentation occurred in three patients (5.7%) in the carotid stenosis group, compared to three (0.9%) who did not have stenosis (P = 0.035). Age, male sex and hypertension were associated with carotid stenosis but hypercholesterolaemia, diabetes and smoking were not. CONCLUSIONS Carotid stenosis ≥ 50% is present in patients with ocular ischaemia in approximately 20% of those with persistent visual loss and in 10% with transient visual loss. Those with carotid stenosis have a higher risk of stroke recurrence and should be considered urgent surgical intervention as other forms of stroke.
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Affiliation(s)
- S F Cheng
- Department of Vascular Surgery, University College Hospital NHS Trust, London, UK.,Division of Surgery and Interventional Science, University College London, UK
| | - A Zarkali
- Department of Stroke, University College Hospital NHS Trust, London, UK
| | - T Richards
- Department of Vascular Surgery, University College Hospital NHS Trust, London, UK.,Division of Surgery and Interventional Science, University College London, UK
| | - R Simister
- Department of Stroke, University College Hospital NHS Trust, London, UK
| | - A Chandratheva
- Department of Stroke, University College Hospital NHS Trust, London, UK
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29
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Zarkali A, Cheng SF, Dados A, Simister R, Chandratheva A. Atrial Fibrillation: An Underestimated Cause of Ischemic Monocular Visual Loss? J Stroke Cerebrovasc Dis 2019; 28:1495-1499. [PMID: 30935808 DOI: 10.1016/j.jstrokecerebrovasdis.2019.03.017] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2018] [Revised: 02/11/2019] [Accepted: 03/05/2019] [Indexed: 11/29/2022] Open
Abstract
INTRODUCTION Atrial fibrillation (AF) is a major cause of ischemic stroke and Transient Ischemic Attack (TIA) and investigation for paroxysmal AF is recommended following an embolic brain event. In contrast, retinal ischemic monocular blindness is traditionally considered most linked to carotid artery disease (CAS) and investigating for AF is less vigilant. We aimed to determine the prevalence of AF in patients with ischemic monocular blindness. METHODS Consecutive records of all patients presenting to a daily TIA clinic with transient or permanent ischemic monocular blindness were reviewed, January 2014-October 2016. RESULTS Of 400 patients, 224 (56.0%) were male, mean age 64.5 years (SD 15.1). A total of 263 (66%) presented with transient and 137 (34%) with permanent ischemic monocular blindness. ECG was performed in 364 patients (91%) but only 211 (52%) had further cardiac monitoring. The vast majority (97.3%) had carotid imaging. Thirty-six patients (9%) were found to have AF while 53 (14%) had ipsilateral CAS. Median ABCD2 score was 1 in AF and non-AF groups. Only 55% of known AF patients were anticoagulated at presentation, despite all having CHADVASC2 score greater than or equal to 1. Patients with AF had more hypertension (P = .004), previous TIA (P = .002), previous stroke (P = .044) and ischemic heart disease (P = .022) with no difference in age (P = .791), diabetes (P = .563), smoking (P = .460) nor hypercholesterolaemia (P = .083). CONCLUSIONS A total of 9% of patients with ischemic monocular blindness had AF. This is an underestimate, as only 53% of patients had prolonged cardiac monitoring. Known AF was suboptimally managed with only 55% receiving anticoagulation despite being eligible.
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Affiliation(s)
- Angeliki Zarkali
- Hyperacute Stroke Unit, University College London Hospital, United Kingdom.
| | - Suk Fun Cheng
- Division of Surgery and Interventional Science, University College London, United Kingdom
| | - Agnes Dados
- Hyperacute Stroke Unit, University College London Hospital, United Kingdom
| | - Robert Simister
- Hyperacute Stroke Unit, University College London Hospital, United Kingdom
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30
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Zarkali A, Cheng S, Dados A, Simister R, Chandratheva A. Undertreatment of Vascular Risk Factors in Patients with Monocular Ischaemic Visual Loss. Cerebrovasc Dis 2018; 45:228-235. [DOI: 10.1159/000489567] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2017] [Accepted: 04/23/2018] [Indexed: 11/19/2022] Open
Abstract
Background and Purpose: Ischaemic visual loss is often considered a lower risk factor than other transient ischaemic attacks (TIA). We aimed to determine the recurrence risk, prevalence and management of vascular risk factors in these patients. Methods: The study took place in the University College Hospital London daily TIA clinic, main referral centre for North-Central London and Moorfields Eye Hospital. Consecutive records for patients with transient (< 24 h) or permanent (> 24 h) ischaemic visual loss were reviewed during the period January 2014–October 2016. Patients diagnosed with temporal arteritis were excluded. Results: Of 400 patients, 224 (56%) were male with mean age 64.5 years (SD 15.1); 263 patients (65.8%) presented with transient and 137 patients (34.2%) with permanent ischaemic visual loss; 51.3% had hypertension (HTN), 35.3% hypercholesterolaemia, 14.5% diabetes, 11.8% ischaemic ocular events, 10.0% ischaemic heart disease, 7.3% atrial fibrillation (AF), 6.3% TIA, 5.3% stroke, and 12.3% were smokers. Median vascular risk factors were 2 (range 1–6), but 122 (30.5%) had ≥3. Those with diabetes (p < 0.001), HTN (p = 0.008), previous myocardial infarction (p = 0.005), or ≥3 vascular risk factors (p = 0.012) were more likely to present with permanent visual loss, while patients with history of transient events, TIA (p = 0.002), or ocular (p = 0.002) presented with transient visual loss. Ninety-day recurrence was 10.5%; this was higher in patients with ≥3 risk factors (hazard ratio 1.42, 95% CI 0.95–2.11, p = 0.111). Patients with past TIA were more likely to be on secondary prevention than those with ocular ischaemia; 60.0 vs. 34.1% received antiplatelets and 76.0 vs. 43.9% statins. At presentation, only 55.2% (16 patients) with known AF were anticoagulated, despite all of them having CHADSVASC ≥1. Conclusions: Approximately one-third of patients with ocular ischaemia had ≥3 vascular risk factors with recurrences higher in these patients. Yet only half of those with previous ischaemic ocular events were on antiplatelets or statins. These patients should be investigated and treated as aggressively as other forms of TIA or stroke.
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31
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Zarkali A, Cousins O, Athauda D, Moses S, Moran N, Harikrishnan S. Glial fibrillary acidic protein antibody-positive meningoencephalomyelitis. Pract Neurol 2018; 18:315-319. [PMID: 29440316 DOI: 10.1136/practneurol-2017-001863] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 01/14/2018] [Indexed: 11/04/2022]
Abstract
Glial fibrillary acidic protein antibody-positive meningoencephalomyelitis is a newly described, possibly under-recognised, severe inflammatory condition of the nervous system. The clinical presentation is variable but most commonly is a combination of meningitis, encephalitis and myelitis; other manifestations may include seizures, psychiatric symptoms and tremor. There is a significant association with malignancies, often occult, and with other autoimmune conditions. Although the disease responds well to corticosteroids acutely, it typically relapses when these are tapered, and so patients need long-term immunosuppression. We report a young man presenting with subacute meningoencephalitis and subsequent myelitis, and discuss the typical presentation and management of this severe but treatable condition.
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Affiliation(s)
- Angeliki Zarkali
- East Kent Neurology Unit, East Kent University Hospitals NHS Foundation Trust, Canterbury, UK
| | - Oliver Cousins
- East Kent Neurology Unit, East Kent University Hospitals NHS Foundation Trust, Canterbury, UK
| | - Dilan Athauda
- East Kent Neurology Unit, East Kent University Hospitals NHS Foundation Trust, Canterbury, UK.,University College London, London, UK
| | - Samuel Moses
- East Kent Microbiology and Virology, East Kent University Hospitals NHS Foundation Trust, Canterbury, UK
| | - Nicholas Moran
- East Kent Neurology Unit, East Kent University Hospitals NHS Foundation Trust, Canterbury, UK.,King's College London, London, UK
| | - Sreedharan Harikrishnan
- East Kent Neurology Unit, East Kent University Hospitals NHS Foundation Trust, Canterbury, UK.,King's College London, London, UK
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32
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Zarkali A, Cheng A, Dados A, Simister R, Chandratheva A. PO264 Prevalence of atrial fibrilation in 395 patients presenting with ocular ischaemic events. J Neurol Neurosurg Psychiatry 2017. [DOI: 10.1136/jnnp-2017-abn.283] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
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33
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Zarkali A, Kumar G, Sakel M, Redmond I, Harikrishnan S. PO160 Atypical transverse myelitis in a patient with newly diagnosed hepatitis c: a case report and review of the literature. J Neurol Neurosurg Psychiatry 2017. [DOI: 10.1136/jnnp-2017-abn.189] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/04/2022]
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34
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Zarkali A, Cheng A, Dados A, Simister R, Chandratheva A. 1115 Undertreatment of vascular risk factors in patients presenting with ischaemic ocular events: results from 395 patients in a tertiary centre. J Neurol Neurosurg Psychiatry 2017. [DOI: 10.1136/jnnp-2017-abn.12] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/04/2022]
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35
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Lux D, Zarkali A, Munro N, Moran N. Vigilance in the myeloma patient: A case of CNS myelomatosis masked by multiple confounders. J Neurol Sci 2017. [DOI: 10.1016/j.jns.2017.08.2100] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
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36
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Lux D, Zarkali A, Harikrishnan S. Cranial neuropathy in chronic inflammatory demyelinating polyradiculoneuropathy: A consideration with variable response to treatment. J Neurol Sci 2017. [DOI: 10.1016/j.jns.2017.08.2204] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
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37
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Sarr-Gonzales S, Zarkali A, Bonifacio G, Englezou C, Manji H, Parton M, Hanna M, Lunn M, Reilly M, Carr A. OPTIMISING THE IVIG SERVICE: AN AUDIT OF MONITORING AND DOSAGE. J Neurol Neurosurg Psychiatry 2016. [DOI: 10.1136/jnnp-2016-315106.2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
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38
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Zarkali A, Bonifacio G, Englezou C, Parsons VVH, Renshaw H, Ingle G, Manji H, Reilly M, Lunn M, Carr A. OPTIMISING IVIG DELIVERY IN A TERTIARY NEUROLOGY CENTRE. J Neurol Neurosurg Psychiatry 2016. [DOI: 10.1136/jnnp-2016-315106.190] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/04/2022]
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Zarkali A, Brown N, Harding N, Grieve J, Adams M, Ganesan V, Simister R, Brown M. LONG-TERM OUTCOMES IN MEDICALLY TREATED MOYAMOYA DISEASE. J Neurol Neurosurg Psychiatry 2016. [DOI: 10.1136/jnnp-2016-315106.12] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/04/2022]
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40
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Zarkali A, Gorgoraptis N, Miller R, John L, Merve A, Thust S, Jager R, Kullmann D, Swayne O. CD8+ encephalitis: a severe but treatable HIV-related acute encephalopathy. Pract Neurol 2016; 17:42-46. [PMID: 27803046 DOI: 10.1136/practneurol-2016-001483] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 10/02/2016] [Indexed: 11/04/2022]
Abstract
Rapidly progressive encephalopathy in an HIV-positive patient presents a major diagnostic and management challenge. CD8+ encephalitis is a severe but treatable form of HIV-related acute encephalopathy, characterised by diffuse perivascular and intraparenchymal CD8+ lymphocytic infiltration. It can occur in patients who are apparently stable on antiretroviral treatment and probably results from viral escape into the central nervous system. Treatment, including high-dose corticosteroids, can give an excellent neurological outcome, even in people with severe encephalopathy and a very poor initial neurological status. We report a woman with CD8+ encephalitis, with a normal CD4 count and undetectable serum viral load, who made a good recovery despite the severity of her presentation.
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Affiliation(s)
| | | | - Robert Miller
- Research Department of Infection and Population Health, University College London, London, UK.,Clinical Research Department, London School of Hygiene and Tropical Medicine, London, UK
| | | | - Ashirwad Merve
- National Hospital for Neurology and Neurosurgery, London, UK
| | - Stefanie Thust
- National Hospital for Neurology and Neurosurgery, London, UK
| | - Rolf Jager
- National Hospital for Neurology and Neurosurgery, London, UK.,Neuroradiological Academic Unit, Department of Brain Repair & Rehabilitation, UCL Institute of Neurology, London, UK
| | - Dimitri Kullmann
- National Hospital for Neurology and Neurosurgery, London, UK.,Institute of Neurology, University College London, London, UK
| | - Orlando Swayne
- National Hospital for Neurology and Neurosurgery, London, UK.,Institute of Neurology, University College London, London, UK
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Affiliation(s)
- R P Finn
- NHS England, Skipton House, London SE1 6LH, UK
| | - C Smith
- NHS England, Skipton House, London SE1 6LH, UK
| | - S Ghafur
- NHS England, Skipton House, London SE1 6LH, UK
| | - A Zarkali
- NHS England, Skipton House, London SE1 6LH, UK
| | - K Adlington
- NHS England, Skipton House, London SE1 6LH, UK
| | - B Winter
- NHS England, Skipton House, London SE1 6LH, UK
| | - B E Keogh
- NHS England, Skipton House, London SE1 6LH, UK
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Adlington K, Finn R, Ghafur S, Smith C, Zarkali A. NHS: a brave new world? Reflections on the Five Year Forward View. Br J Hosp Med (Lond) 2014; 75:606-7. [PMID: 25383425 DOI: 10.12968/hmed.2014.75.11.606] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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Sames E, Li C, Roads E, Flanegan K, Zarkali A. AB0458 The Effect of Subcutaneously Administered Methotrexate on Mean Corpuscular Volume in the Treatment of Rheumatoid Arthritis. Ann Rheum Dis 2014. [DOI: 10.1136/annrheumdis-2014-eular.2519] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/04/2022]
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Zarkali A, Karageorgopoulos DE, Rafailidis PI, Falagas ME. Frequency of the off-label use of monoclonal antibodies in clinical practice: a systematic review of the literature. Curr Med Res Opin 2014; 30:471-80. [PMID: 24127749 DOI: 10.1185/03007995.2013.855186] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
BACKGROUND The monoclonal antibodies represent novel therapeutic options for many clinical entities. This study aimed to study the frequency of the off-label use to total use of different monoclonal antibodies in clinical practice. METHODS This study systematically searched the PubMed and Scopus databases for relevant studies. RESULTS Fifteen studies were considered eligible for inclusion in this review. Eight of the included studies referred to the off-label use of anti-neoplastic monoclonal antibodies, three referred to immunosuppressive ones, and four to other types of monoclonal antibodies. The most studied anti-neoplastic monoclonal antibody was rituximab; which was prescribed off-label at a frequency varying between 16-75%, mostly for an unapproved diagnosis. Bevacizumab was prescribed off-label for age-related macular degeneration more often than ranibizumab, the approved monoclonal antibody for this condition. Of the immunosuppressive monoclonal antibodies, infliximab was used off-label in an average of 15.4% (range=2.8-25%) and adalimumab in 10.5% (range=0-15.4% in different years). CONCLUSION The frequency of off-label use of different types of monoclonal antibodies varies, but appears to be considerably high for specific monoclonal antibodies or indications. In certain examples, this might reflect implementation into clinical practice of relevant scientific data, albeit not of the strength or quality that suffices for receipt of regulatory approval. In others, it might relate to the sub-optimal effectiveness and considerable toxicity of the conventional therapies. Still, the clinician should bear in mind the potential costs and toxicity that can be associated with off-label use of monoclonal antibodies.
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Affiliation(s)
- Angeliki Zarkali
- Alfa Institute of Biomedical Sciences (AIBS) , Marousi, Athens , Greece
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Zarkali A, Black D, Smee E, Deshraj A, Smallwood N. Planning ahead: Improving escalation plans before the weekend. BMJ Qual Improv Report 2014; 2:bmjquality_uu203854.w1730. [PMID: 26734241 PMCID: PMC4663829 DOI: 10.1136/bmjquality.u203854.w1730] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Subscribe] [Scholar Register] [Received: 01/20/2014] [Revised: 02/11/2014] [Indexed: 11/03/2022]
Abstract
Handover is the system by which responsibility for patient care is transferred between healthcare professionals. A significant aspect of handover is the existence of an escalation plan for each patient in case of deterioration over the weekend. According to the Royal College of Physicians, all patients should have a clear escalation plan documented in the notes before a weekend, since parent medical teams (Consultant team in charge of care) are best placed to make these decisions. If left to on-call teams, at a time of deterioration over a weekend, they might not have all available information, the patient might be unable to be involved in the decisions, and the family might not be consulted. With this is mind, we decided to analyse the existing handover process in a medium sized district general hospital, with the aim of improving the process and the documentation of escalation plans. The results from our retrospective analysis of the system in place revealed a significant lack of documentation of escalation plans in the medical notes. Three sample wards were selected to analyse the current handover system and test proposed measures before hospital-wide implementation. After trialling of a physical handover meeting in addition to the existing intranet system and a proforma for the Friday ward round, the documentation of escalation plans in the patients' notes improved from 9.1% to 41.1%. Based on these results, as well as formal feedback from junior doctors and informal feedback from other staff, the physical handover meeting and Friday ward round proforma will be implemented throughout the Trust. Our interventions led to an improvement in the documentation of escalation plans in our hospital, thus saving precious time in the event of a patient's deterioration. This also ensures that families and patients are involved in the decision making process and kept informed, and reduces the burden for the weekend on-call teams.
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Zarkali A, Rallidis M, Fragou A, Angouras D, Triantafyllidi H, Athanasia S, Tsaganos T, Anagnostopoulos K, Dimitriadis G, Giamarellou H, Ikonomopoulos T, Kremastinos D, Anastasiou-Nana M, Petrikkos G, Raptis S, Rokkas C, Giannitsioti E. P16 CHANGING PROFILE OF INFECTIVE ENDOCARDITIS IN A TERTIARY UNIVERSITY HOSPITAL: A 6-YEAR EXPERIENCE (2005–2010). Int J Antimicrob Agents 2013. [DOI: 10.1016/s0924-8579(13)70040-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
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Falagas ME, Zarkali A, Karageorgopoulos DE, Bardakas V, Mavros MN. The impact of article length on the number of future citations: a bibliometric analysis of general medicine journals. PLoS One 2013; 8:e49476. [PMID: 23405060 PMCID: PMC3566179 DOI: 10.1371/journal.pone.0049476] [Citation(s) in RCA: 103] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2012] [Accepted: 10/11/2012] [Indexed: 01/07/2023] Open
Abstract
Background The number of citations received is considered an index of study quality and impact. We aimed to examine the factors associated with the number of citations of published articles, focusing on the article length. Methods Original human studies published in the first trimester of 2006 in 5 major General Medicine journals were analyzed with regard to the number of authors and of author-affiliated institutions, title and abstract word count, article length (number of print pages), number of bibliographic references, study design, and 2006 journal impact factor (JIF). A multiple linear regression model was employed to identify the variables independently associated with the number of article citations received through January 2012. Results On univariate analysis the JIF, number of authors, article length, study design (interventional/observational and prospective/retrospective), title and abstract word count, number of author-affiliated institutions, and number of references were all associated with the number of citations received. On multivariate analysis with the logarithm of citations as the dependent variable, only article length [regression coefficient: 14.64 (95% confidence intervals: (5.76–23.50)] and JIF [3.37 (1.80–4.948)] independently predicted the number of citations. The variance of citations explained by these parameters was 51.2%. Conclusion In a sample of articles published in major General Medicine journals, in addition to journal impact factors, article length and number of authors independently predicted the number of citations. This may reflect a higher complexity level and quality of longer and multi-authored studies.
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Affiliation(s)
- Matthew E Falagas
- Alfa Institute of Biomedical Sciences (AIBS), Marousi, Athens, Greece.
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