1
|
Thomson AR, Pasanta D, Arichi T, Puts NA. Neurometabolite differences in Autism as assessed with Magnetic Resonance Spectroscopy: A systematic review and meta-analysis. Neurosci Biobehav Rev 2024; 162:105728. [PMID: 38796123 DOI: 10.1016/j.neubiorev.2024.105728] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2024] [Revised: 04/23/2024] [Accepted: 05/14/2024] [Indexed: 05/28/2024]
Abstract
1H-Magnetic Resonance Spectroscopy (MRS) is a non-invasive technique that can be used to quantify the concentrations of metabolites in the brain in vivo. MRS findings in the context of autism are inconsistent and conflicting. We performed a systematic review and meta-analysis of MRS studies measuring glutamate and gamma-aminobutyric acid (GABA), as well as brain metabolites involved in energy metabolism (glutamine, creatine), neural and glial integrity (e.g. n-acetyl aspartate (NAA), choline, myo-inositol) and oxidative stress (glutathione) in autism cohorts. Data were extracted and grouped by metabolite, brain region and several other factors before calculation of standardised effect sizes. Overall, we find significantly lower concentrations of GABA and NAA in autism, indicative of disruptions to the balance between excitation/inhibition within brain circuits, as well as neural integrity. Further analysis found these alterations are most pronounced in autistic children and in limbic brain regions relevant to autism phenotypes. Additionally, we show how study outcome varies due to demographic and methodological factors , emphasising the importance of conforming with standardised consensus study designs and transparent reporting.
Collapse
Affiliation(s)
- Alice R Thomson
- Department of Forensic and Neurodevelopmental Sciences, King's College London, UK; MRC Centre for Neurodevelopmental Disorders, King's College London, UK; Centre for the Developing Brain, King's College London, London, UK
| | - Duanghathai Pasanta
- Department of Forensic and Neurodevelopmental Sciences, King's College London, UK
| | - Tomoki Arichi
- MRC Centre for Neurodevelopmental Disorders, King's College London, UK; Centre for the Developing Brain, King's College London, London, UK
| | - Nicolaas A Puts
- Department of Forensic and Neurodevelopmental Sciences, King's College London, UK; MRC Centre for Neurodevelopmental Disorders, King's College London, UK.
| |
Collapse
|
2
|
Weng G, Slotboom J, Schucht P, Ermiş E, Wiest R, Klöppel S, Peter J, Zubak I, Radojewski P. Simultaneous multi-region detection of GABA+ and Glx using 3D spatially resolved SLOW-editing and EPSI-readout at 7T. Neuroimage 2024; 286:120511. [PMID: 38184158 DOI: 10.1016/j.neuroimage.2024.120511] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2023] [Revised: 12/07/2023] [Accepted: 01/04/2024] [Indexed: 01/08/2024] Open
Abstract
GABA+ and Glx (glutamate and glutamine) are widely studied metabolites, yet the commonly used magnetic resonance spectroscopy (MRS) techniques have significant limitations, including sensitivity to B0 and B1+-inhomogeneities, limited bandwidth of MEGA-pulses, high SAR which is accentuated at 7T. To address these limitations, we propose SLOW-EPSI method, employing a large 3D MRSI coverage and achieving a high resolution down to 0.26 ml. Simulation results demonstrate the robustness of SLOW-editing for both GABA+ and Glx against B0 and B1+-inhomogeneities within the range of [-0.3, +0.3] ppm and [40 %, 250 %], respectively. Two protocols, both utilizing a 70 mm thick FOV slab, were employed to target distinct brain regions in vivo, differentiated by their orientation: transverse and tilted. Protocol 1 (n = 11) encompassed 5 locations (cortical gray matter, white matter, frontal lobe, parietal lobe, and cingulate gyrus). Protocol 2 (n = 5) involved 9 locations (cortical gray matter, white matter, frontal lobe, occipital lobe, cingulate gyrus, caudate nucleus, hippocampus, putamen, and inferior thalamus). Quantitative analysis of GABA+ and Glx was conducted in a stepwise manner. First, B1+/B1--inhomogeneities were corrected using water reference data. Next, GABA+ and Glx values were calculated employing spectral fitting. Finally, the GABA+ level for each selected region was compared to the global Glx within the same subject, generating the GABA+/Glx_global ratio. Our findings from two protocols indicate that the GABA+/Glx_global level in cortical gray matter was approximately 16 % higher than in white matter. Elevated GABA+/Glx_global levels acquired with protocol 2 were observed in specific regions such as the caudate nucleus (0.118±0.067), putamen (0.108±0.023), thalamus (0.092±0.036), and occipital cortex (0.091±0.010), when compared to the cortical gray matter (0.079±0.012). Overall, our results highlight the effectiveness of SLOW-EPSI as a robust and efficient technique for accurate measurements of GABA+ and Glx at 7T. In contrast to previous SVS and 2D-MRSI based editing sequences with which only one or a limited number of brain regions can be measured simultaneously, the method presented here measures GABA+ and Glx from any brain area and any arbitrarily shaped volume that can be flexibly selected after the examination. Quantification of GABA+ and Glx across multiple brain regions through spectral fitting is achievable with a 9-minute acquisition. Additionally, acquisition times of 18-27 min (GABA+) and 9-18 min (Glx) are required to generate 3D maps, which are constructed using Gaussian fitting and peak integration.
Collapse
Affiliation(s)
- Guodong Weng
- Institute for Diagnostic and Interventional Neuroradiology, Inselspital, University Hospital and University of Bern, Switzerland; Translational Imaging Center, sitem-insel, Bern, Switzerland.
| | - Johannes Slotboom
- Institute for Diagnostic and Interventional Neuroradiology, Inselspital, University Hospital and University of Bern, Switzerland; Translational Imaging Center, sitem-insel, Bern, Switzerland
| | - Philippe Schucht
- Department of Neurosurgery, Inselspital, University Hospital and University of Bern, Switzerland
| | - Ekin Ermiş
- Department of Radiation Oncology, Inselspital, University Hospital and University of Bern, Switzerland
| | - Roland Wiest
- Institute for Diagnostic and Interventional Neuroradiology, Inselspital, University Hospital and University of Bern, Switzerland; Translational Imaging Center, sitem-insel, Bern, Switzerland
| | - Stefan Klöppel
- University Hospital of Old Age Psychiatry and Psychotherapy, University of Bern, Bern, Switzerland
| | - Jessica Peter
- University Hospital of Old Age Psychiatry and Psychotherapy, University of Bern, Bern, Switzerland
| | - Irena Zubak
- Department of Neurosurgery, Inselspital, University Hospital and University of Bern, Switzerland
| | - Piotr Radojewski
- Institute for Diagnostic and Interventional Neuroradiology, Inselspital, University Hospital and University of Bern, Switzerland; Translational Imaging Center, sitem-insel, Bern, Switzerland
| |
Collapse
|
3
|
Bédard P, Panyakaew P, Cho HJ, Hallett M, Horovitz SG. Multimodal imaging of essential tremor and dystonic tremor. Neuroimage Clin 2022; 36:103247. [PMID: 36451353 PMCID: PMC9668651 DOI: 10.1016/j.nicl.2022.103247] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2022] [Revised: 10/21/2022] [Accepted: 10/23/2022] [Indexed: 11/06/2022]
Abstract
Despite recent advances in tremor and dystonia classification, it remains difficult to discriminate essential tremor from dystonic tremor as they are similar in appearance and no biomarker exists. Further, tremor can appear in the same or a different body part than the dystonia. The aim of the current study was to better understand the differential pathophysiology of these tremors. We designed a cross-sectional case-control study and recruited 16 patients with essential tremor, 16 patients with dystonic tremor, and 17 age-matched healthy volunteers. We used multi-modal imaging combining resting-state functional MRI, diffusion tensor imaging, and magnetic resonance spectroscopy. We measured functional connectivity of resting-state fMRI to assess connectivity in the tremor network, fractional anisotropy and mean diffusivity with diffusion tensor imaging, and GABA+, Glutamate/Glutamine, Choline, and N-Acetylaspartate with spectroscopy (adjusted to Creatine). Our results showed reduced functional connectivity of resting-state fMRI between the cerebellum and dentate nucleus bilaterally for the essential tremor group, but not the dystonic tremor group, compared to healthy volunteers. There was higher fractional anisotropy in the middle cerebellar peduncle bilaterally for the dystonic tremor group compared to the essential tremor group as well as for essential tremor group compared to healthy volunteers. There was also higher fractional anisotropy in the red nucleus and corticospinal tract for essential tremor and dystonic tremor groups compared to healthy volunteers. We also showed reduced mean diffusivity in the cerebellum of both essential tremor and dystonic tremor groups compared to healthy volunteers. Finally, we found elevated GABA+/Cr in the cerebellum of the essential tremor and dystonic tremor groups compared to healthy volunteers, but no difference emerged between essential tremor and dystonic tremor groups. We did not find group differences in the other metabolites. Our results indicate cerebellar alterations in essential tremor and dystonic tremor patients compared to healthy volunteers, and further changes in the cerebellum network for the dystonic tremor patients. suggesting that the cerebellum is affected differently in both tremors.
Collapse
Affiliation(s)
- Patrick Bédard
- Human Motor Control Section, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, MD 20892-1428, USA
| | - Pattamon Panyakaew
- Human Motor Control Section, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, MD 20892-1428, USA,Chulalongkorn Center of Excellence for Parkinson’s Disease & Related Disorders, Department of Medicine, Faculty of Medicine, Chulalongkorn University and King Chulalongkorn Memorial Hospital, Thai Red Cross Society, Bangkok 10330, Thailand
| | - Hyun-Joo Cho
- Human Motor Control Section, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, MD 20892-1428, USA
| | - Mark Hallett
- Human Motor Control Section, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, MD 20892-1428, USA
| | - Silvina G. Horovitz
- Human Motor Control Section, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, MD 20892-1428, USA,Corresponding author.
| |
Collapse
|
4
|
Shyu C, Chavez S, Boileau I, Foll BL. Quantifying GABA in Addiction: A Review of Proton Magnetic Resonance Spectroscopy Studies. Brain Sci 2022; 12:brainsci12070918. [PMID: 35884725 PMCID: PMC9316447 DOI: 10.3390/brainsci12070918] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2022] [Revised: 07/07/2022] [Accepted: 07/09/2022] [Indexed: 02/04/2023] Open
Abstract
Gamma-aminobutyric acid (GABA) signaling plays a crucial role in drug reward and the development of addiction. Historically, GABA neurochemistry in humans has been difficult to study due to methodological limitations. In recent years, proton magnetic resonance spectroscopy (1H-MRS, MRS) has emerged as a non-invasive imaging technique that can detect and quantify human brain metabolites in vivo. Novel sequencing and spectral editing methods have since been developed to allow for quantification of GABA. This review outlines the clinical research utilization of 1H-MRS in understanding GABA neurochemistry in addiction and summarizes current literature that reports GABA measurements by MRS in addiction. Research on alcohol, nicotine, cocaine, and cannabis addiction all suggest medications that modulate GABA signaling may be effective in reducing withdrawal, craving, and other addictive behaviors. Thus, we discuss how improvements in current MRS techniques and design can optimize GABA quantification in future studies and explore how monitoring changes to brain GABA could help identify risk factors, improve treatment efficacy, further characterize the nature of addiction, and provide crucial insights for future pharmacological development.
Collapse
Affiliation(s)
- Claire Shyu
- Translational Addiction Research Laboratory, Centre for Addiction and Mental Health, Toronto, ON M5S 2S1, Canada;
- Brain Health Imaging Centre, Centre for Addiction and Mental Health, Toronto, ON M5T 1R8, Canada; (S.C.); (I.B.)
- Department of Pharmacology and Toxicology, University of Toronto, Toronto, ON M5S 1A8, Canada
| | - Sofia Chavez
- Brain Health Imaging Centre, Centre for Addiction and Mental Health, Toronto, ON M5T 1R8, Canada; (S.C.); (I.B.)
- Institute of Medical Sciences, University of Toronto, Toronto, ON M5S 1A8, Canada
- Centre for Addiction and Mental Health, Campbell Family Mental Health Research Institute, Toronto, ON M5T 1R8, Canada
- Department of Psychiatry, Division of Brain and Therapeutics, University of Toronto, Toronto, ON M5T 1R8, Canada
| | - Isabelle Boileau
- Brain Health Imaging Centre, Centre for Addiction and Mental Health, Toronto, ON M5T 1R8, Canada; (S.C.); (I.B.)
- Department of Pharmacology and Toxicology, University of Toronto, Toronto, ON M5S 1A8, Canada
- Institute of Medical Sciences, University of Toronto, Toronto, ON M5S 1A8, Canada
- Centre for Addiction and Mental Health, Campbell Family Mental Health Research Institute, Toronto, ON M5T 1R8, Canada
- Department of Psychiatry, Division of Brain and Therapeutics, University of Toronto, Toronto, ON M5T 1R8, Canada
| | - Bernard Le Foll
- Translational Addiction Research Laboratory, Centre for Addiction and Mental Health, Toronto, ON M5S 2S1, Canada;
- Brain Health Imaging Centre, Centre for Addiction and Mental Health, Toronto, ON M5T 1R8, Canada; (S.C.); (I.B.)
- Department of Pharmacology and Toxicology, University of Toronto, Toronto, ON M5S 1A8, Canada
- Institute of Medical Sciences, University of Toronto, Toronto, ON M5S 1A8, Canada
- Centre for Addiction and Mental Health, Campbell Family Mental Health Research Institute, Toronto, ON M5T 1R8, Canada
- Department of Psychiatry, Division of Brain and Therapeutics, University of Toronto, Toronto, ON M5T 1R8, Canada
- Centre for Addiction and Mental Health, Concurrent Outpatient Medical & Psychosocial Addiction Support Services, Toronto, ON M6J 1H4, Canada
- Centre for Addiction and Mental Health, Acute Care Program, Toronto, ON M6J 1H3, Canada
- Department of Family and Community Medicine, University of Toronto, Toronto, ON M5G 1V7, Canada
- Waypoint Centre for Mental Health Care, Waypoint Research Institute, 500 Church Street, Penetanguishene, ON L9M 1G3, Canada
- Correspondence: ; Tel.: +1-416-535-8501
| |
Collapse
|
5
|
Ondo W. Enhancing GABA inhibition is the next generation of medications for essential tremor. INTERNATIONAL REVIEW OF NEUROBIOLOGY 2022; 163:317-334. [PMID: 35750368 DOI: 10.1016/bs.irn.2022.02.007] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/15/2023]
Abstract
γ-Aminobutyric acid (GABA) is the most prevalent inhibitory CNS neurotransmitter. Activating GABA-A receptors hyperpolarizes cells via Cl- influx, which inhibits action potentials. Although the exact pathophysiologies of tremor are incompletely understood, proposed neuroanatomy extensively implicates GABA pathways. Pathological studies and imaging studies also show GABA abnormalities in patients with ET. Most importantly, medications that activate GABA-A receptors, such as primidone, often improve tremor. Ongoing clinical trials and physiology research should further refine potential future GABAergic targets and treatments, which are currently the most promising targets for pharmacological intervention.
Collapse
Affiliation(s)
- William Ondo
- Houston Methodist Hospital, Weill Cornel Medical School, Houston, TX, United States.
| |
Collapse
|
6
|
Bellows S, Jimenez-Shahed J. Is essential tremor a disorder of GABA dysfunction? No. INTERNATIONAL REVIEW OF NEUROBIOLOGY 2022; 163:285-310. [PMID: 35750366 DOI: 10.1016/bs.irn.2022.02.006] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/15/2023]
Abstract
Although essential tremor is common, its underlying pathophysiology remains uncertain, and several hypotheses seek to explain the tremor mechanism. The GABA hypothesis states that disinhibition of deep cerebellar neurons due to reduced GABAergic input from Purkinje cells results in increased pacemaker activity, leading to rhythmic output to the thalamo-cortical circuit and resulting in tremor. However, some neuroimaging, spectroscopy, and pathology studies have not shown a clear or consistent GABA deficiency in essential tremor, and animal models have indicated that large reductions of Purkinje cell inhibition may improve tremor. Instead, tremor is increasingly attributable to dysfunction in oscillating networks, where altered (but not necessarily reduced) inhibitory signaling can result in tremor. Hypersynchrony of Purkinje cell activity may account for excessive oscillatory cerebellar output, with potential contributions along multiple sites of the olivocerebellar loop. Although older animal tremor models, such as harmaline tremor, have explored contributions from the inferior olivary body, increasing evidence has pointed to the role of aberrant climbing fiber synaptic organization in oscillatory cerebellar activity and tremor generation. New animal models such as hotfoot17j mice, which exhibit abnormal climbing fiber organization due to mutations in Grid2, have recapitulated many features of ET. Similar abnormal climbing fiber architecture and excessive cerebellar oscillations as measured by EEG have been found in humans with essential tremor. Further understanding of hypersynchrony and excessive oscillatory activity in ET phenotypes may lead to more targeted and effective treatment options.
Collapse
|
7
|
Gironell A. Is essential tremor a disorder of primary GABA dysfunction? Yes. INTERNATIONAL REVIEW OF NEUROBIOLOGY 2022; 163:259-284. [PMID: 35750365 PMCID: PMC9446196 DOI: 10.1016/bs.irn.2022.02.005] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
Dysfunction in gamma-aminobutyric acid (GABA) neurotransmission has emerged as a prime suspect for the underlying neurochemical dysfunction in essential tremor (ET). This dysfunction has been termed the GABA hypothesis. We review findings to date supporting the 4 steps in this hypothesis in studies of cerebrospinal fluid, pathology, genetics, animal models, imaging, computational models, and human drugs, while not overlooking the evidence of negative studies and controversies. It remains to be elucidated whether reduced GABAergic tone is a primary contributing factor to ET pathophysiology, a consequence of altered Purkinje cell function, or even a result of Purkinje cell death. More studies are clearly needed to confirm both the neurodegenerative nature of ET and the reduction in GABA activity in the cerebellum. Also necessary is to test further therapies to enhance GABA transmission specifically focused on the cerebellar area.
Collapse
Affiliation(s)
- Alexandre Gironell
- Movement Disorders Unit, Department of Neurology, Sant Pau Hospital, Autonomous University of Barcelona, Catalonia, Spain.
| |
Collapse
|
8
|
Kosmowska B, Wardas J. The Pathophysiology and Treatment of Essential Tremor: The Role of Adenosine and Dopamine Receptors in Animal Models. Biomolecules 2021; 11:1813. [PMID: 34944457 PMCID: PMC8698799 DOI: 10.3390/biom11121813] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2021] [Revised: 11/25/2021] [Accepted: 11/30/2021] [Indexed: 12/13/2022] Open
Abstract
Essential tremor (ET) is one of the most common neurological disorders that often affects people in the prime of their lives, leading to a significant reduction in their quality of life, gradually making them unable to independently perform the simplest activities. Here we show that current ET pharmacotherapy often does not sufficiently alleviate disease symptoms and is completely ineffective in more than 30% of patients. At present, deep brain stimulation of the motor thalamus is the most effective ET treatment. However, like any brain surgery, it can cause many undesirable side effects; thus, it is only performed in patients with an advanced disease who are not responsive to drugs. Therefore, it seems extremely important to look for new strategies for treating ET. The purpose of this review is to summarize the current knowledge on the pathomechanism of ET based on studies in animal models of the disease, as well as to present and discuss the results of research available to date on various substances affecting dopamine (mainly D3) or adenosine A1 receptors, which, due to their ability to modulate harmaline-induced tremor, may provide the basis for the development of new potential therapies for ET in the future.
Collapse
Affiliation(s)
| | - Jadwiga Wardas
- Department of Neuropsychopharmacology, Maj Institute of Pharmacology Polish Academy of Sciences, 31-343 Kraków, Poland;
| |
Collapse
|
9
|
GABAergic Modulation in Movement Related Oscillatory Activity: A Review of the Effect Pharmacologically and with Aging. Tremor Other Hyperkinet Mov (N Y) 2021; 11:48. [PMID: 34824891 PMCID: PMC8588888 DOI: 10.5334/tohm.655] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2021] [Accepted: 09/26/2021] [Indexed: 11/20/2022] Open
Abstract
Gamma-aminobutyric acid (GABA) is a ubiquitous inhibitory neurotransmitter critical to the control of movement both cortically and subcortically. Modulation of GABA can alter the characteristic rest as well as movement-related oscillatory activity in the alpha (8-12 Hz), beta (13-30 Hz, and gamma (60-90 Hz) frequencies, but the specific mechanisms by which GABAergic modulation can modify these well-described changes remains unclear. Through pharmacologic GABAergic modulation and evaluation across the age spectrum, the contributions of GABA to these characteristic oscillatory activities are beginning to be understood. Here, we review how baseline GABA signaling plays a key role in motor networks and in cortical oscillations detected by scalp electroencephalography and magnetoencephalography. We also discuss the data showing specific alterations to baseline movement related oscillatory changes from pharmacologic intervention on GABAergic tone as well as with healthy aging. These data provide greater insight into the physiology of movement and may help improve future development of novel therapeutics for patients who suffer from movement disorders.
Collapse
|
10
|
Holtbernd F, Shah NJ. Imaging the Pathophysiology of Essential Tremor-A Systematic Review. Front Neurol 2021; 12:680254. [PMID: 34220687 PMCID: PMC8244929 DOI: 10.3389/fneur.2021.680254] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2021] [Accepted: 05/04/2021] [Indexed: 11/28/2022] Open
Abstract
Background: The pathophysiology underlying essential tremor (ET) still is poorly understood. Recent research suggests a pivotal role of the cerebellum in tremor genesis, and an ongoing controversy remains as to whether ET constitutes a neurodegenerative disorder. In addition, mounting evidence indicates that alterations in the gamma-aminobutyric acid neurotransmitter system are involved in ET pathophysiology. Here, we systematically review structural, functional, and metabolic neuroimaging studies and discuss current concepts of ET pathophysiology from an imaging perspective. Methods: We conducted a PubMed and Scopus search from 1966 up to December 2020, entering essential tremor in combination with any of the following search terms and their corresponding abbreviations: positron emission tomography (PET), single-photon emission computed tomography (SPECT), magnetic resonance imaging (MRI), magnetic resonance spectroscopy (MRS), and gamma-aminobutyric acid (GABA). Results: Altered functional connectivity in the cerebellum and cerebello-thalamico-cortical circuitry is a prevalent finding in functional imaging studies. Reports from structural imaging studies are less consistent, and there is no clear evidence for cerebellar neurodegeneration. However, diffusion tensor imaging robustly points toward microstructural cerebellar changes. Radiotracer imaging suggests that the dopaminergic axis is largely preserved in ET. Similarly, measurements of nigral iron content and neuromelanin are unremarkable in most studies; this is in contrast to Parkinson's disease (PD). PET and MRS studies provide limited evidence for cerebellar and thalamic GABAergic dysfunction. Conclusions: There is robust evidence indicating that the cerebellum plays a key role within a multiple oscillator tremor network which underlies tremor genesis. However, whether cerebellar dysfunction relies on a neurodegenerative process remains unclear. Dopaminergic and iron imaging do not suggest a substantial overlap of ET with PD pathophysiology. There is limited evidence for alterations of the GABAergic neurotransmitter system in ET. The clinical, demographical, and genetic heterogeneity of ET translates into neuroimaging and likely explains the various inconsistencies reported.
Collapse
Affiliation(s)
- Florian Holtbernd
- Institute of Neuroscience and Medicine (INM-4/INM-11), Forschungszentrum Juelich GmbH, Juelich, Germany.,JARA-BRAIN Institute Molecular Neuroscience and Neuroimaging, Forschungszentrum Juelich GmbH, Rheinisch-Westfaelische Technische Hochschule Aachen University, Aachen, Germany.,Department of Neurology, Rheinisch-Westfaelische Technische Hochschule Aachen University, Aachen, Germany
| | - N Jon Shah
- Institute of Neuroscience and Medicine (INM-4/INM-11), Forschungszentrum Juelich GmbH, Juelich, Germany.,JARA-BRAIN Institute Molecular Neuroscience and Neuroimaging, Forschungszentrum Juelich GmbH, Rheinisch-Westfaelische Technische Hochschule Aachen University, Aachen, Germany.,Department of Neurology, Rheinisch-Westfaelische Technische Hochschule Aachen University, Aachen, Germany
| |
Collapse
|
11
|
Buijink AWG, Prent N, Puts NA, Schrantee A, Potters WV, van Rootselaar AF. GABA, Glutamate, and NAA Levels in the Deep Cerebellar Nuclei of Essential Tremor Patients. Front Neurol 2021; 12:664735. [PMID: 34025569 PMCID: PMC8136412 DOI: 10.3389/fneur.2021.664735] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2021] [Accepted: 04/12/2021] [Indexed: 01/10/2023] Open
Abstract
Background: Essential tremor is among the commonly observed movement disorders in clinical practice, however the exact pathophysiological mechanisms underlying tremor are unknown. It has been suggested that Purkinje cell alterations play a causal factor in tremorgenesis. Altered levels of inhibitory (GABA) and excitatory (glutamate+glutamine, Glx) neurotransmitters could be markers for Purkinje cell alterations. We hypothesize that GABA and Glx levels in the dentate nuclei could be differentially altered in patients responsive to either anticonvulsants or β-adrenergic blockers. Methods: In this explorative study in patients with essential tremor, we measured gamma-aminobutyric acid (GABA) and glutamate+glutamine (Glx) levels in the dentate nucleus region using 1H-magnetic resonance spectroscopy (MRS) in seven patients using propranolol, five patients using anticonvulsants, and eight healthy controls. Results: There were no group differences with respect to GABA+/Cr, Glx/Cr, NAA/Cr, and GABA+/Glx ratios. There was no correlation with tremor severity. Discussion: Our results are in line with previously published studies; however, additional studies on a larger number of patients are warranted to confirm these findings. Furthermore medication-subgroups did not exhibit differences with respect to GABA+/Cr, Glx/Cr, NAA/Cr, and GABA+/Glx ratios. A recent study, of similar size, found an inverse association between tremor severity and the GABA+/Glx ratio in the cerebellum of essential tremor patients. We were unable to replicate these findings. The field of tremor research is plagued by heterogeneous results, and we would caution against drawing firm conclusions based on pilot studies.
Collapse
Affiliation(s)
- Arthur W. G. Buijink
- Department of Neurology and Clinical Neurophysiology, Amsterdam University Medical Centers, Amsterdam Neuroscience, University of Amsterdam, Amsterdam, Netherlands
| | - Naomi Prent
- Department of Neurology and Clinical Neurophysiology, Amsterdam University Medical Centers, Amsterdam Neuroscience, University of Amsterdam, Amsterdam, Netherlands
| | - Nicolaas A. Puts
- Department of Forensic and Neurodevelopmental Sciences, Sackler Institute for Translational Neurodevelopment, Institute of Psychiatry, Psychology, and Neuroscience, King's College London, London, United Kingdom
| | - Anouk Schrantee
- Department of Radiology and Nuclear Medicine, Amsterdam University Medical Centers, University of Amsterdam, Amsterdam, Netherlands
| | - Wouter V. Potters
- Department of Neurology and Clinical Neurophysiology, Amsterdam University Medical Centers, Amsterdam Neuroscience, University of Amsterdam, Amsterdam, Netherlands
| | - Anne-Fleur van Rootselaar
- Department of Neurology and Clinical Neurophysiology, Amsterdam University Medical Centers, Amsterdam Neuroscience, University of Amsterdam, Amsterdam, Netherlands
| |
Collapse
|
12
|
Schneider N, Potschka H, Reese S, Wielaender F, Fischer A. Imepitoin for treatment of idiopathic head tremor syndrome in dogs: A randomized, blinded, placebo-controlled study. J Vet Intern Med 2020; 34:2571-2581. [PMID: 33159484 PMCID: PMC7694850 DOI: 10.1111/jvim.15955] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2020] [Revised: 10/18/2020] [Accepted: 10/21/2020] [Indexed: 12/14/2022] Open
Abstract
Background Idiopathic head tremor syndrome is a paroxysmal movement disorder of unknown etiology. Spontaneous remission may occur, but owners may request treatment in severely affected dogs with continued episodes. Controlled studies of the disease are not available. Hypothesis/Objectives A drug with gamma amino butyric acid‐ergic and anxiolytic effects will decrease head tremor episodes. Animals Twenty‐four dogs with severe nonremitting head tremor and presumptive clinical diagnosis of idiopathic head tremor syndrome. Methods Prospective, blinded, placebo‐controlled clinical trial to compare imepitoin with placebo in dogs with frequent episodes of idiopathic head tremor. Evaluation of efficacy used the quotient T2/T1 that represented prolongation of the head tremor‐free period compared to a 3‐month baseline. A dog was considered a responder if tremors subsided or if the head tremor‐free period was 3× longer than the longest period during baseline (T2/T1 ≥ 3). Sample size calculations considered a large effect of imepitoin on T2/T1 (Cohen's d = 0.8). Results There were no responders in the placebo group (0/12). In the imepitoin group, the responder rate was 17% (2/12; P = .18) with T2/T1 3.8 and 4.0. Mean T2/T1 was 1.0 ± 1.4 in the imepitoin and 0.4 ± 0.4 in the placebo group (P = .37). Conclusion and Clinical Importance Imepitoin did not result in a significant overall benefit. Future studies should focus on treatment of subgroups with a common pathophysiology and similar comorbidities.
Collapse
Affiliation(s)
- Nina Schneider
- Centre for Clinical Veterinary Medicine, LMU Munich, Munich, Germany
| | - Heidrun Potschka
- Institute of Pharmacology, Toxicology, and Pharmacy, LMU Munich, Munich, Germany
| | - Sven Reese
- Department of Veterinary Sciences, Faculty of Veterinary Medicine, LMU Munich, Munich, Germany
| | | | - Andrea Fischer
- Centre for Clinical Veterinary Medicine, LMU Munich, Munich, Germany
| |
Collapse
|