Adaptive structural changes in the motor cortex and white matter in Parkinson's disease

The effect of pallidal stimulation on sleep outcomes and related brain connectometries in Parkinson's disease

Sleep difficulties affect up to 98% of Parkinson's disease (PD) patients and are often not well treated. How globus pallidus internus (GPi)-DBS could help is less understood. We retrospectively analyzed sleep outcomes in 32 PD patients after GPi-DBS with a two-year follow-up. We observed high heterogeneity in sleep response to pallidal stimulation: 16 patients showed clinically meaningful improvement, 9 had minor changes, and 7 experienced worsened sleep quality, with no overall significant change on the Parkinson's Disease Sleep Scale-2 (P = 0.19). Further analysis revealed that stimulation of the left sensorimotor GPi was significantly associated with sleep improvement. Fiber tracts from the left sensorimotor GPi to the bilateral sensorimotor cortex, right GPi, brainstem, and bilateral cerebellum were linked to better sleep, while projections to the left hippocampus correlated with worsened sleep. These findings may guide personalized GPi-DBS lead placement to optimize sleep outcomes in PD.

Microstructural correlates of olfactory dysfunction in Parkinson's Disease: a systematic review of diffusion MRI studies

Olfactory dysfunction (OD) is a non-motor symptom of Parkinson's Disease, affecting 75-95% of the patients. This symptom usually emerges before the clinical diagnosis, and patients with OD present with more severe forms of PD and need higher doses of therapy. It remains unknown whether OD is just a mere non-motor symptom or if it is a part of a series of pathological changes in different brain regions of the affected patients. We performed a systematic review to find the microstructural correlates of OD in people with PD. The systematic search in PubMed, Scopus, Embase, and Web of Science yielded ten eligible studies. Assessments in most included studies were inconclusive. However, we found variable brain regions and tracts associated with OD. The most repeated areas included the primary olfactory cortex, gyrus rectus, inferior fronto-occipital fasciculus, inferior longitudinal fasciculus, corticospinal tract, uncinate fasciculus, cingulum, and cerebellar peduncle. Despite some limitations, we pointed out the microstructural correlates of OD, which were also present in areas other than the olfactory system. These findings imply that OD might be a manifestation of an unknown, greater pathology in the brain of patients with PD.

Human α-synuclein aggregation activates ferroptosis leading to parvalbumin interneuron degeneration and motor learning impairment

The accumulation of α-synuclein induces neuronal loss in midbrain nuclei and leads to the disruption of motor circuits, while the pathology of α-synuclein in cortical regions remains elusive. To better characterize cortical synucleinopathy, here we generate a mouse model with the overexpression of human α-synuclein in the primary motor cortex (M1) of mice. A combination of molecular, in vivo recording, and behavioral approaches reveal that cortical expression of human α-synuclein results in the overexcitation of cortical pyramidal neurons (PNs), which are regulated by the decreased inhibitory inputs from parvalbumin-interneurons (PV-INs) to impair complex motor skill learning. Further mechanistic dissections reveal that human α-synuclein aggregation activates ferroptosis, contributing to PV-IN degeneration and motor circuit dysfunction. Taken together, the current study adds more knowledge to the emerging role and pathogenic mechanism of ferroptosis in neurodegenerative diseases.

Motor Cortical Neuronal Hyperexcitability Associated with α-Synuclein Aggregation

Dysfunction of the cerebral cortex is thought to underlie motor and cognitive impairments in Parkinson disease (PD). While cortical function is known to be suppressed by abnormal basal ganglia output following dopaminergic degeneration, it remains to be determined how the deposition of Lewy pathology disrupts cortical circuit integrity and function. Moreover, it is also unknown whether cortical Lewy pathology and midbrain dopaminergic degeneration interact to disrupt cortical function in late-stage. To begin to address these questions, we injected α-synuclein (αSyn) preformed fibrils (PFFs) into the dorsolateral striatum of mice to seed αSyn pathology in the cortical cortex and induce degeneration of midbrain dopaminergic neurons. Using this model system, we reported that αSyn aggregates accumulate in the motor cortex in a layer- and cell-subtype-specific pattern. Particularly, intratelencephalic neurons (ITNs) showed earlier accumulation and greater extent of αSyn aggregates relative to corticospinal neurons (CSNs). Moreover, we demonstrated that the intrinsic excitability and inputs resistance of αSyn aggregates-bearing ITNs in the secondary motor cortex (M2) are increased, along with a noticeable shrinkage of cell bodies and loss of dendritic spines. Last, neither the intrinsic excitability of CSNs nor their thalamocortical input was altered by a partial striatal dopamine depletion associated with αSyn pathology. Our results documented motor cortical neuronal hyperexcitability associated with αSyn aggregation and provided a novel mechanistic understanding of cortical circuit dysfunction in PD.

⍺-Synuclein levels in Parkinson's disease - Cell types and forms that contribute to pathogenesis

Parkinson's disease (PD) has two main pathological hallmarks, the loss of nigral dopamine neurons and the proteinaceous aggregations of ⍺-synuclein (⍺Syn) in neuronal Lewy pathology. These two co-existing features suggest a causative association between ⍺Syn aggregation and the underpinning mechanism of neuronal degeneration in PD. Both increased levels and post-translational modifications of ⍺Syn can contribute to the formation of pathological aggregations of ⍺Syn in neurons. Recent studies have shown that the protein is also expressed by multiple types of non-neuronal cells in the brain and peripheral tissues, suggesting additional roles of the protein and potential diversity in non-neuronal pathogenic triggers. It is important to determine (1) the threshold levels triggering ⍺Syn to convert from a biological to a pathologic form in different brain cells in PD; (2) the dominant form of pathologic ⍺Syn and the associated post-translational modification of the protein in each cell type involved in PD; and (3) the cell type associated biological processes impacted by pathologic ⍺Syn in PD. This review integrates these aspects and speculates on potential pathological mechanisms and their impact on neuronal and non-neuronal ⍺Syn in the brains of patients with PD.

Motor Cortical Neuronal Hyperexcitability Associated with α-Synuclein Aggregation

Dysfunction of the cerebral cortex is thought to underlie motor and cognitive impairments in Parkinson disease (PD). While cortical function is known to be suppressed by abnormal basal ganglia output following dopaminergic degeneration, it remains to be determined how the deposition of Lewy pathology disrupts cortical circuit integrity and function. Moreover, it is also unknown whether cortical Lewy pathology and midbrain dopaminergic degeneration interact to disrupt cortical function in late-stage. To begin to address these questions, we injected α-synuclein (αSyn) preformed fibrils (PFFs) into the dorsolateral striatum of mice to seed αSyn pathology in the cortical cortex and induce degeneration of midbrain dopaminergic neurons. Using this model system, we reported that αSyn aggregates accumulate in the motor cortex in a layer- and cell-subtype-specific pattern. Particularly, intratelencephalic neurons (ITNs) showed earlier accumulation and greater extent of αSyn aggregates relative to corticospinal neurons (CSNs). Moreover, we demonstrated that the intrinsic excitability and inputs resistance of αSyn aggregates-bearing ITNs in the secondary motor cortex (M2) are increased, along with a noticeable shrinkage of cell bodies and loss of dendritic spines. Last, neither the intrinsic excitability of CSNs nor their thalamocortical input was altered by a partial striatal dopamine depletion associated with αSyn pathology. Our results documented motor cortical neuronal hyperexcitability associated with αSyn aggregation and provided a novel mechanistic understanding of cortical circuit dysfunction in PD.

Emerging insights into Lipocalin-2: Unraveling its role in Parkinson's Disease

Parkinson's disease (PD) ranks as the second most prevalent neurodegenerative disorder globally, marked by a complex pathogenesis. Lipocalin-2 (LCN2) emerges as a crucial factor during the progression of PD. Belonging to the lipocalin family, LCN2 is integral to several biological functions, including glial cell activation, iron homeostasis regulation, immune response, inflammatory reactions, and oxidative stress mitigation. Substantial research has highlighted marked increases in LCN2 expression within the substantia nigra (SN), cerebrospinal fluid (CSF), and blood of individuals with PD. This review focuses on the pathological roles of LCN2 in neuroinflammation, aging, neuronal damage, and iron dysregulation in PD. It aims to explore the underlying mechanisms of LCN2 in the disease and potential therapeutic targets that could inform future treatment strategies.

Dysfunction of motor cortices in Parkinson's disease

The cerebral cortex has long been thought to be involved in the pathophysiology of motor symptoms of Parkinson's disease. The impaired cortical function is believed to be a direct and immediate effect of pathologically patterned basal ganglia output, mediated to the cerebral cortex by way of the ventral motor thalamus. However, recent studies in humans with Parkinson's disease and in animal models of the disease have provided strong evidence suggesting that the involvement of the cerebral cortex is much broader than merely serving as a passive conduit for subcortical disturbances. In the present review, we discuss Parkinson's disease-related changes in frontal cortical motor regions, focusing on neuropathology, plasticity, changes in neurotransmission, and altered network interactions. We will also examine recent studies exploring the cortical circuits as potential targets for neuromodulation to treat Parkinson's disease.

Imaging Procedure and Clinical Studies of [18F]FP-CIT PET

N-3-[18F]fluoropropyl-2β-carbomethoxy-3β-4-iodophenyl nortropane ([18F]FP-CIT) is a radiopharmaceutical for dopamine transporter (DAT) imaging using positron emission tomography (PET) to detect dopaminergic neuronal degeneration in patients with parkinsonian syndrome. [18F]FP-CIT was granted approval by the Ministry of Food and Drug Safety in 2008 as the inaugural radiopharmaceutical for PET imaging, and it has found extensive utilization across numerous institutions in Korea. This review article presents an imaging procedure for [18F]FP-CIT PET to aid nuclear medicine physicians in clinical practice and systematically reviews the clinical studies associated with [18F]FP-CIT PET.

Longitudinal brain changes in Parkinson's disease with severe olfactory deficit

INTRODUCTION

Olfactory dysfunction and REM sleep behavior disorder (RBD) are associated with distinct cognitive trajectories in the course of Parkinson's disease (PD). The underlying neurobiology for this relationship remains unclear but may involve distinct patterns of neurodegeneration. This study aimed to examine longitudinal cortical atrophy and thinning in early-stage PD with severe olfactory deficit (anosmia) without and with concurrent probable RBD.

METHODS

Longitudinal MRI data over four years of 134 de novo PD and 49 healthy controls (HC) from the Parkinson Progression Marker Initiative (PPMI) cohort were analyzed using a linear mixed-effects model. Patients were categorized into those with anosmia by the University of Pennsylvania Smell Identification Test (UPSIT) score ≤ 18 (AO+) and those without (UPSIT score > 18, AO-). The AO+ group was further subdivided into AO+ with probable RBD (AO+RBD+) and without (AO+RBD-) for subanalysis.

RESULTS

Compared to subjects without baseline anosmia, the AO+ group exhibited greater longitudinal declines in both volume and thickness in the bilateral parahippocampal gyri and right transverse temporal gyrus. Patients with concurrent anosmia and RBD showed more extensive longitudinal declines in cortical volume and thickness, involving additional brain regions including the bilateral precuneus, left inferior temporal gyrus, right paracentral gyrus, and right precentral gyrus.

CONCLUSIONS

The atrophy/thinning patterns in early-stage PD with severe olfactory dysfunction include regions that are critical for cognitive function and could provide a structural basis for previously reported associations between severe olfactory deficit and cognitive decline in PD. Concurrent RBD might enhance the dynamics of cortical changes.

Longitudinal Associations of Magnetic Susceptibility with Clinical Severity in Parkinson's Disease

BACKGROUND

Dementia is common in Parkinson's disease (PD), but there is wide variation in its timing. A critical gap in PD research is the lack of quantifiable markers of progression, and methods to identify early stages of dementia. Atrophy-based magnetic resonance imaging (MRI) has limited sensitivity in detecting or tracking changes relating to PD dementia, but quantitative susceptibility mapping (QSM), sensitive to brain tissue iron, shows potential for these purposes.

OBJECTIVE

The objective of the paper is to study, for the first time, the longitudinal relationship between cognition and QSM in PD in detail.

METHODS

We present a longitudinal study of clinical severity in PD using QSM, including 59 PD patients (without dementia at study onset), and 22 controls over 3 years.

RESULTS

In PD, increased baseline susceptibility in the right temporal cortex, nucleus basalis of Meynert, and putamen was associated with greater cognitive severity after 3 years; and increased baseline susceptibility in basal ganglia, substantia nigra, red nucleus, insular cortex, and dentate nucleus was associated with greater motor severity after 3 years. Increased follow-up susceptibility in these regions was associated with increased follow-up cognitive and motor severity, with further involvement of hippocampus relating to cognitive severity. However, there were no consistent increases in susceptibility over 3 years.

CONCLUSIONS

Our study suggests that QSM may predict changes in cognitive severity many months prior to overt cognitive involvement in PD. However, we did not find robust longitudinal changes in QSM over the course of the study. Additional tissue metrics may be required together with QSM for it to monitor progression in clinical practice and therapeutic trials. © 2024 The Authors. Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Society.

The delayed effect of rotenone on the relative content of brain isatin-binding proteins of rats with experimental parkinsonism

Isatin (indoldione-2,3) is an endogenous biological regulator found in the brain, peripheral tissues, and biological fluids of humans and animals. Its biological activity is realized via isatin-binding proteins, many of which were identified during proteomic profiling of the brain of mice and rats. A number of these proteins are related to the development of neurodegenerative diseases. Previously, using a model of experimental Parkinsonism induced by a seven-day course of rotenone injections, we have observed behavioral disturbances, as well as changes in the profile and relative content of brain isatin-binding proteins. In this study, we have investigated behavioral responses and the relative content of brain isatin-binding proteins in rats with rotenone-induced Parkinsonism 5 days after the last administration of this neurotoxin. Despite the elimination of rotenone, animals exhibited motor and coordination impairments. Proteomic profiling of isatin-binding proteins revealed changes in the relative content of 120 proteins (the relative content of 83 proteins increased and that of 37 proteins decreased). Comparison of isatin-binding proteins characterized by the changes in the relative content observed in the brain right after the last injection of rotenone (n=16) and 5 days later (n=11) revealed only two common proteins (glyceraldehyde-3-phosphate dehydrogenase and subunit B of V-type proton ATPase). However, most of these proteins are associated with neurodegeneration, including Parkinson's and Alzheimer's diseases.

Radiomic tractometry reveals tract-specific imaging biomarkers in white matter

Tract-specific microstructural analysis of the brain's white matter (WM) using diffusion MRI has been a driver for neuroscientific discovery with a wide range of applications. Tractometry enables localized tissue analysis along tracts but relies on bare summary statistics and reduces complex image information along a tract to few scalar values, and so may miss valuable information. This hampers the applicability of tractometry for predictive modelling. Radiomics is a promising method based on the analysis of numerous quantitative image features beyond what can be visually perceived, but has not yet been used for tract-specific analysis of white matter. Here we introduce radiomic tractometry (RadTract) and show that introducing rich radiomics-based feature sets into the world of tractometry enables improved predictive modelling while retaining the localization capability of tractometry. We demonstrate its value in a series of clinical populations, showcasing its performance in diagnosing disease subgroups in different datasets, as well as estimation of demographic and clinical parameters. We propose that RadTract could spark the establishment of a new generation of tract-specific imaging biomarkers with benefits for a range of applications from basic neuroscience to medical research.

White matter injury across neurodegenerative disease

Oligodendrocytes (OLs), the myelin-generating cells of the central nervous system (CNS), are active players in shaping neuronal circuitry and function. It has become increasingly apparent that injury to cells within the OL lineage plays a central role in neurodegeneration. In this review, we focus primarily on three degenerative disorders in which white matter loss is well documented: Alzheimer's disease (AD), Parkinson's disease (PD), and amyotrophic lateral sclerosis (ALS). We discuss clinical data implicating white matter injury as a key feature of these disorders, as well as shared and divergent phenotypes between them. We examine the cellular and molecular mechanisms underlying the alterations to OLs, including chronic neuroinflammation, aggregation of proteins, lipid dysregulation, and organellar stress. Last, we highlight prospects for therapeutic intervention targeting the OL lineage to restore function.

Fiber-Specific White Matter Alterations in Parkinson's Disease Patients with GBA Gene Mutations

BACKGROUND

Patients with Parkinson's disease (PD) carrying GBA gene mutations (GBA-PD) have a more aggressive disease course than those with idiopathic PD (iPD).

OBJECTIVE

The objective of this study was to investigate fiber-specific white matter (WM) differences in nonmedicated patients with early-stage GBA-PD and iPD using fixel-based analysis, a novel technique to assess tract-specific WM microstructural and macrostructural features comprehensively.

METHODS

Fixel-based metrics, including microstructural fiber density (FD), macrostructural fiber-bundle cross section (FC), and a combination of FD and FC (FDC), were compared among 30 healthy control subjects, 16 patients with GBA-PD, and 35 patients with iPD. Associations between FDC and clinical evaluations were also explored using multiple linear regression analyses.

RESULTS

Patients with GBA-PD showed significantly lower FD in the fornix and superior longitudinal fasciculus than healthy control subjects, and lower FC in the corticospinal tract (CST) and lower FDC in the CST, middle cerebellar peduncle, and striatal-thalamo-cortical pathways than patients with iPD. Contrarily, patients with iPD showed significantly higher FC and FDC in the CST and striatal-thalamo-cortical pathways than healthy control subjects. In addition, lower FDC in patients with GBA-PD was associated with reduced glucocerebrosidase enzyme activity, lower cerebrospinal fluid total α-synuclein levels, lower Montreal Cognitive Assessment scores, lower striatal binding ratio, and higher Unified Parkinson's Disease Rating Scale Part III scores.

CONCLUSIONS

We report reduced fiber-specific WM density and bundle cross-sectional size in patients with GBA-PD, suggesting neurodegeneration linked to glucocerebrosidase deficiency, α-synuclein accumulation, and poorer cognition and motor functions. Conversely, patients with iPD showed increased fiber bundle size, likely because of WM reorganization. © 2023 The Authors. Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Society.

White matter changes in Parkinson's disease

Parkinson's disease (PD) is the second most common neurodegenerative disease after Alzheimer's disease (AD). It is characterized by a progressive loss of dopaminergic neurons in the substantia nigra pars compacta (SNc) and the formation of Lewy bodies (LBs). Although PD is primarily considered a gray matter (GM) disease, alterations in white matter (WM) have gained increasing attention in PD research recently. Here we review evidence collected by magnetic resonance imaging (MRI) techniques which indicate WM abnormalities in PD, and discuss the correlations between WM changes and specific PD symptoms. Then we summarize transcriptome and genome studies showing the changes of oligodendrocyte (OLs)/myelin in PD. We conclude that WM abnormalities caused by the changes of myelin/OLs might be important for PD pathology, which could be potential targets for PD treatment.

Adenosine A2A receptor availability in cerebral gray and white matter of patients with Parkinson's disease

OBJECTIVE

Atrophic changes in cerebral gray matter of patients with PD have been reported extensively. There is evidence suggesting an association between cortical gyrification changes and white matter abnormalities. Adenosine A2A receptors have been shown to be upregulated in cerebral white matter and on reactive astrocytes in preclinical models of neurodegenerative diseases. We, therefore, sought to investigate in vivo changes in A2A receptor availability in cerebral gray and white matter of PD patients and its association with gray matter atrophy.

METHODS

Eighteen patients with PD without dyskinesia and seven healthy controls were enrolled for this study. Brain MRI and dynamic PET scan was acquired with [11C]TMSX radioligand which binds selectively to A2A receptors. FreeSurfer software was used to segment cerebral gray and white matter structures. The resulting masks were used to calculate region specific volumes and to derive distribution volume ratios (DVRs), after co-registration with PET images, for the quantification of specific [11C]TMSX binding.

RESULTS

We showed an increase in A2A receptor availability in frontal (P < 0.001) and parietal (P < 0.001) white matter and a decrease in occipital (P = 0.02) gray matter of PD patients as compared to healthy controls. A decrease in gray matter volume ratios was observed in frontal (P < 0.01), parietal (P < 0.001), temporal (P < 0.01) and occipital (P < 0.01) ROIs in patients with PD versus healthy controls.

CONCLUSIONS

Our results suggest a role of A2A receptor-based signaling in the neurodegenerative changes seen in the cerebral gray and white matter of patients with PD.

Predicting impact of Deep Brain Stimulation on Non-motor symptoms of Parkinson's disease

This is the largest study on Radiomics analysis looking into the impact of Deep Brain Stimulation on Non-Motor Symptoms (NMS) of Parkinson's disease. Preoperative brain white matter radiomics of 120 patients integrated with clinical variables were used to predict the DBS effect on NMS after 1 year from the surgery. Patients were classified "suboptimal" vs "good" based on a 10% or more improvement in NMS score. The combined Radiomics-Clinical Random Forrest (RF) model achieved an AUC of 0.96, Accuracy of 0.91, Sensitivity of 0.94 and Specificity of 0.88. The Youden's index showed optimal threshold for the RF of 0.535. The confusion matrix of the RF classifier gave a TPR of 0.92 and a FPR of 0.03. This corresponds to a PPV of 0.93 and a NPV of 0.93. The predictive models can be easily interpreted and after careful large-scale validation be integrated in assisting clinicians and patients to make informed decisions.Clinical Relevance- This paper shows the lesser studied positive impact of Deep Brain Stimulation on Non motor symptoms of Parkinson's disease while allows clinicians to predict non responders to the therapy.

Efficacy of rehabilitation robot-assisted gait training on lower extremity dyskinesia in patients with Parkinson's disease: A systematic review and meta-analysis

BACKGROUND

Robot-assisted training is used as a new rehabilitation training method for the treatment of motor dysfunction in neurological diseases. Robot-assisted gait training (RAGT) has been reported to treat motor dysfunction in patients with Parkinson's disease (PD). The purpose of this study was to summarize previous clinical studies comparing the effectiveness of RAGT and conventional training for lower extremity dyskinesia in PD patients.

METHODS

PubMed, Cochrane library, Scopus, Embase, EBSCO, Web of Science, CNKI, and Wanfang databases were searched. This study included all randomized controlled trials (RCTs) compared lower extremity RAGT with conventional training on motor impairment in PD patients. The retrieval time limit is from the establishment of the database to October 2022. Two researchers independently screened the literature, extracted data, assessed the risk of bias of included studies, and then used RevMan 5.3 software for meta-analysis.

RESULTS

A total of 14 RCTs with 572 patients were included. The results showed that compared with the control group, RAGT significantly improved the motor function evaluation-related indicators 10MWT, 6MWT, TUG and UPDRS III, 10MWT [MD= 0.08, 95 % CI (0.01, 0.14), P = 0.03], 6MWT [MD= 42.83, 95 % CI (22.05, 63.62), P < 0.0001], TUG[MD= -1.81, 95 % CI (-2.55, -1.08), P < 0.0001], UPDRS III [MD= - 3.82, 95 % CI (-4.27, -3.37), P < 0.00001]; For the balance function evaluation index BBS [MD= 3.33, 95 % CI (2.76, 3.89), P < 0.00001], the above results were significantly different significance.

CONCLUSION

The currently limited evidence suggests that RAGT provides evidence for the effectiveness of lower extremity motor function and balance dysfunction, and RAGT can significantly improve motor and balance function in PD patients.