Resequencing the complete SNCA locus in Indian patients with Parkinson's disease.

The genetic loci implicated in familial Parkinson's disease (PD) have limited generalizability to the Indian PD population. We tested mutations and the frequency of known mutations in the SNCA gene in a PD cohort from India. We selected 298 PD cases and 301 age-matched controls for targeted resequencing (before QC), along with 363 PD genomes of Indian ancestry and 1029 publicly available whole genomes from India as healthy controls (IndiGenomes), to determine the frequency of monogenic SNCA mutations. The raw sequence reads were analyzed using an in-house analysis pipeline, allowing the detection of small variants and structural variants using Manta. The in-depth analysis of the SNCA locus did not identify missense or structural variants, including previously identified SNCA mutations, in the Indian population. The familial forms of SNCA gene variants do not play a major role in the Indian PD population and this warrants further research in the under-represented population.

Quantifying abnormal writing kinematics in writer's cramp using a novel software platform.

BACKGROUND: Writer's cramp is a task-specific focal hand dystonia, which is diagnosed clinically. Quantification of defect in WC is done using clinical scales, while digitized platforms are lacking. OBJECTIVE: To design and test a platform that can differentiate and quantify the abnormal kinematics of writing using a software interface and to validate it in adult-onset isolated writer's cramp (WC). METHODS: A native platform was designed using Java and Wacom Intuos pro tablet and the data analyzed using a MATLAB-based platform called Large Data-Based Evaluation of Kinematics in Handwriting (LEKH). We standardized this new platform by comparing the handwriting between patients with WC and age, and gender and education-matched healthy controls, using standard tasks to assess the kinematics. RESULTS: Comparison of the writing of right-handed WC patients (N = 21) and 39 healthy controls (N = 39) showed that patients differed from controls in the frequency of strokes (P < 0.001), number of inversions of velocity (P < 0.001), number of breaks (P = 0.02), air time and paper time (P < 0.001). CONCLUSIONS: Using the LEKH platform, the kinematic profile of patients with WC could be differentiated from healthy controls. Studies in larger samples will be needed to derive statistical models that can differentiate the flexion and extension types of WC which can help in muscle selection and to quantify the effects of treatment.

A Novel PINK1 p.F385S Loss-of-Function Mutation in an Indian Family with Parkinson's Disease.

BACKGROUND: Most Parkinson's disease (PD) loci have shown low prevalence in the Indian population, highlighting the need for further research. OBJECTIVE: The aim of this study was to characterize a novel phosphatase tensin homolog-induced serine/threonine kinase 1 (PINK1) mutation causing PD in an Indian family. METHODS: Exome sequencing of a well-characterized Indian family with PD. A novel PINK1 mutation was studied by in silico modeling using AlphaFold2, expression of mutant PINK1 in human cells depleted of functional endogenous PINK1, followed by quantitative image analysis and biochemical assessment. RESULTS: We identified a homozygous chr1:20648535-20648535 T>C on GRCh38 (p.F385S) mutation in exon 6 of PINK1, which was absent in 1029 genomes from India and in other known databases. PINK1 F385S lies within the highly conserved Deutsche Forschungsgemeinschaft (DFG) motif, destabilizes its active state, and impairs phosphorylation of ubiquitin at serine 65 and proper engagement of parkin upon mitochondrial depolarization. CONCLUSIONS: We characterized a novel nonconservative mutation in the DFG motif of PINK1, which causes loss of its ubiquitin kinase activity and inhibition of mitophagy. © 2024 The Authors. Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Society.

A Review on Implantable Neuroelectrodes.

The efficacy of every neuromodulation modality depends upon the characteristics of the electrodes used to stimulate the chosen target. The geometrical, chemical, mechanical and physical configuration of electrodes used in neurostimulation affects several performance attributes like stimulation efficiency, selectivity, tissue response, etc. The efficiency of stimulation in relation to electrode impedance is influenced by the electrode material and/or its geometry. The nature of the electrode material determines the charge transfer across the electrode-tissue interface, which also relates to neuronal tissue damage. Electrode morphology or configuration pattern can facilitate the modulation of extracellular electric field (field shaping). This enables selective activation of neurons and minimizes side effects. Biocompatibility and biostability of the electrode materials or electrode coating have a role in glial formation and tissue damage. Mechanical and electrochemical stability (corrosion resistance) determines the long-term efficacy of any neuromodulation technique. Here, a review of electrodes typically used for implantable neuromodulation is discussed. Factors affecting the performance of electrodes like stimulation efficiency, selectivity and tissue responses to the electrode-tissue interface are discussed. Technological advancements to improve electrode characteristics are also included.

Cerebellar and basal ganglia structural connections in humans: Effect of aging and relation with memory and learning.

Introduction: The cerebellum and basal ganglia were initially considered anatomically distinct regions, each connected via thalamic relays which project to the same cerebral cortical targets, such as the motor cortex. In the last two decades, transneuronal viral transport studies in non-human primates showed bidirectional connections between the cerebellum and basal ganglia at the subcortical level, without involving the cerebral cortical motor areas. These findings have significant implications for our understanding of neurodevelopmental and neurodegenerative diseases. While these subcortical connections were established in smaller studies on humans, their evolution with natural aging is less understood. Methods: In this study, we validated and expanded the previous findings of the structural connectivity within the cerebellum-basal ganglia subcortical network, in a larger dataset of 64 subjects, across different age ranges. Tractography and fixel-based analysis were performed on the 3 T diffusion-weighted dataset using Mrtrix3 software, considering fiber density and cross-section as indicators of axonal integrity. Tractography of the well-established cerebello-thalamo-cortical tract was conducted as a control. We tested the relationship between the structural white matter integrity of these connections with aging and with the performance in different domains of Addenbrooke's Cognitive Examination. Results: Tractography analysis isolated connections from the dentate nucleus to the contralateral putamen via the thalamus, and reciprocal tracts from the subthalamic nucleus to the contralateral cerebellar cortex via the pontine nuclei. Control tracts of cerebello-thalamo-cortical tracts were also isolated, including associative cerebello-prefrontal tracts. A negative linear relationship was found between the fiber density of both the ascending and descending cerebellum-basal ganglia tracts and age. Considering the cognitive assessments, the fiber density values of cerebello-thalamo-putaminal tracts correlated with the registration/learning domain scores. In addition, the fiber density values of cerebello-frontal and subthalamo-cerebellar (Crus II) tracts correlated with the cognitive assessment scores from the memory domain. Conclusion: We validated the structural connectivity within the cerebellum-basal ganglia reciprocal network, in a larger dataset of human subjects, across wider age range. The structural features of the subcortical cerebello-basal ganglia tracts in human subjects display age-related neurodegeneration. Individual morphological variability of cerebellar tracts to the striatum and prefrontal cortex was associated with different cognitive functions, suggesting a functional contribution of cerebellar tracts to cognitive decline with aging. This study offers new perspectives to consider the functional role of these pathways in motor learning and the pathophysiology of movement disorders involving the cerebellum and striatum.

Depotentiation of associative plasticity is intact in Parkinson's disease with mild dyskinesia.

OBJECTIVE: Depotentiation of homosynaptic plasticity of the primary motor cortex (M1) is impaired in patients with Parkinson's disease (PD) who have developed dyskinesias. In this exploratory study, we tested whether this holds true for heterosynaptic plasticity induced by paired associative stimulation (PAS). METHODS: Dyskinetic (n=11) and Non-dyskinetic (n=11), levodopa-treated PD patients were tested in M1 with PAS25ms alone, PAS25ms preceded by continuous theta-burst stimulation of the cerebellum (cTBSCB-PAS) as a method to evoke a larger plastic response in M1, and each of these two interventions followed by a depotentiation protocol (cTBS150pulses) to M1. RESULTS: PAS25ms and cTBSCB-PAS25ms induced long-term potentiation (LTP)-like responses in both groups of PD patients, with cTBSCB significantly boosting the plastic response. Both these LTP-like responses could be depotentiated by cTBS150, in both groups of patients. CONCLUSIONS: Cerebellar stimulation enhances heterosynaptic plasticity in PD irrespective of dyskinesias. Depotentiation mechanisms of heterosynaptic plasticity are preserved in PD patients, including those with dyskinesias. The lack of depotentiation of LTP-like plasticity as a hallmark of dyskinesia in PD patients is not absolute. The ability to depotentiate LTP-like plasticity may potentially depend on the type of plasticity induced (homosynaptic or heterosynaptic), the circuits involved in these responses and the adequacy of dopaminergic stimulation.

Cognitive outcome following bilateral subthalamic nucleus deep brain stimulation for Parkinson's disease-a comparative observational study in Indian patients.

BACKGROUND: Deep brain stimulation (DBS) of the subthalamic nucleus (STN) improves motor symptoms and motor complications of Parkinson's disease (PD). The intervention is expected to result in some cognitive changes, the nature of which is not uniform across the studies which have reported them. PD itself is associated with progressive cognitive decline and hence longitudinal follow-up studies with medically managed control group of patients are needed to explore the cognitive deficits attributable to DBS. METHODS: We conducted a prospective comparative observational study to assess the effects of bilateral STN DBS on cognition. Cognitive functions were assessed at baseline and after a minimum of two years after surgery, and compared with baseline and follow-up assessments in patients on medical management alone. RESULTS: Thirty-four patients with PD who underwent bilateral STN DBS and thirty-four medically managed patients participated in the study. At a mean follow-up of around 33 months, we found a significant decline in verbal fluency scores in the DBS group compared to those on medical management alone (1.15 ± 1.23 vs 0.59 ± 0.93, p = 0.034) and a trend for decline was noted in digit span test. There was no difference in the performance in tests addressing other cognitive domains, or tests of global cognitive function. No patient developed dementia. Motor functions and activities of daily living (ADL) were significantly better in the surgical group. CONCLUSION: STN DBS results in minor deficits in executive functions, particularly verbal fluency. These may be inconsequential, considering the marked improvement in motor functions and ADL.

Gender differences in progressive supranuclear palsy.

The gender differences in progressive supranuclear palsy (PSP) are not extensively studied. The objective of this study was to determine the gender differences in the phenotypic expression and progression in PSP. We did a retrospective review of medical records of patients diagnosed with PSP over a 21-year period. The interval between disease onset and attainment of the five clinical disability milestones namely wheel chair dependency, unintelligible speech, severe dysphagia, severe cognitive impairment and urinary catheterization was used to determine the progression. Data was analysed from the case records of 334 patients with PSP. 209 patients (62.2%) were male and 125 (37.4%) among the patients were women (male:female ratio = 1.6:1). Males had older age at onset with longer duration of illness at time of presentation. Tremors were more common, PSP-P phenotype was more frequent and time to attain wheelchair dependency was earlier in males. Falls within 1 year of disease onset, apathy and executive dysfunction were more frequent and time to attain unintelligible speech, severe dysphagia and cognitive impairment were earlier in females. This study in a large cohort of clinically diagnosed cases of PSP has showed that gender differences exist in PSP in terms of clinical characteristics, progression of the disease.

Myoclonus- A Review.

Myoclonus is a hyperkinetic movement disorder characterized by a sudden, brief, involuntary jerk. Positive myoclonus is caused by abrupt muscle contractions, while negative myoclonus by sudden cessation of ongoing muscular contractions. Myoclonus can be classified in various ways according to body distribution, relation to activity, neurophysiology, and etiology. The neurophysiological classification of myoclonus by means of electrophysiological tests is helpful in guiding the best therapeutic strategy. Given the diverse etiologies of myoclonus, a thorough history and detailed physical examination are key to the evaluation of myoclonus. These along with basic laboratory testing and neurophysiological studies help in narrowing down the clinical possibilities. Though symptomatic treatment is required in the majority of cases, treatment of the underlying etiology should be the primary aim whenever possible. Symptomatic treatment is often not satisfactory, and a combination of different drugs is often required to control the myoclonus. This review addresses the etiology, classification, clinical approach, and management of myoclonus.

Plastic responsiveness of motor cortex to paired associative stimulation depends on cerebellar input.

OBJECTIVE: The extent of plastic responses of motor cortex (M1) to paired associative stimulation (PAS) varies among healthy subjects. Continuous theta-burst stimulation (cTBS) of cerebellum enhances the mean PAS-induced plasticity in groups of healthy subjects. We tested whether the initial status of Responder or Non -Responder to PAS, influenced the effect of cerebellar stimulation on PAS-induced plasticity. METHODS: We assessed in 19 young healthy volunteers (8 Responders, 11 Non-Responders to PAS), how cTBS and iTBS (intermittent TBS) applied to the cerebellum before a PAS protocol influenced the plastic responsiveness of M1 to PAS. We tested whether the PAS-induced plastic effects could be depotentiated by a short cTBS protocol applied to M1 shortly after PAS and whether cerebellar stimulation influenced GABA-ergic intracortical inhibition and M1 plasticity in parallel. RESULTS: Cerebellar cTBS restored the M1 response to PAS in Non-Responders while cerebellar iTBS turned the potentiating response to PAS to a depressive response in both groups. The depotentiation protocol abolished both responses. CONCLUSION: Non-Responder status to PAS is a state of M1 amenable to bidirectional plastic modulation when primed by a change in cerebello-thalamic drive. SIGNIFICANCE: The meaning of lack of responsiveness to certain protocols probing plasticity should be reconsidered.

Cross-sectional analysis of the Parkinson's disease Non-motor International Longitudinal Study baseline non-motor characteristics, geographical distribution and impact on quality of life.

Growing evidence suggests that non-motor symptoms (NMS) in Parkinson's disease (PD) have differential progression patterns that have a different natural history from motor progression and may be geographically influenced. We conducted a cross-sectional analysis of 1607 PD patients of whom 1327 were from Europe, 208 from the Americas, and 72 from Asia. The primary objective was to assess baseline non-motor burden, defined by Non-Motor Symptoms Scale (NMSS) total scores. Other aims included identifying the factors predicting quality of life, differences in non-motor burden between drug-naïve and non-drug-naïve treated patients, and non-motor phenotypes across different geographical locations. Mean age was 65.9 ± 10.8 years, mean disease duration 6.3 ± 5.6 years, median Hoehn and Yahr stage was 2 (2-3), and 64.2% were male. In this cohort, mean NMSS scores were 46.7 ± 37.2. Differences in non-motor burden and patterns differed significantly between drug-naïve participants, those with a disease duration of less than five years, and those with a duration of five years or over (p ≤ 0.018). Significant differences were observed in geographical distribution (NMSS Europe: 46.4 ± 36.3; Americas: 55.3 ± 42.8; Asia: 26.6 ± 25.1; p < 0.001), with differences in sleep/fatigue, urinary, sexual, and miscellaneous domains (p ≤ 0.020). The best predictor of quality of life was the mood/apathy domain (ß = 0.308, p < 0.001). This global study reveals that while non-motor symptoms are globally present with severe NMS burden impacting quality of life in PD, there appear to be differences depending on disease duration and geographical distribution.

Apraxia of Lid Opening in Subthalamic Nucleus Deep Brain Stimulation for Parkinson's Disease-Frequency, Risk Factors and Response to Treatment.

BACKGROUND: New-onset apraxia of lid opening (ALO) is reported to occur in Parkinson's disease (PD) patients following Deep Brain Stimulation (DBS). There are only few systematic studies on this uncommon disorder of eyelid movements. OBJECTIVES: We aimed to examine the frequency, temporal evolution, predisposing factors and response to treatment, of new-onset ALO in PD patients who underwent bilateral subthalamic nucleus (STN) DBS. METHODS: We retrospectively reviewed the data of patients who underwent STN DBS at our centre between 1999 and 2017, with a minimum of 2 years of follow up after surgery. RESULTS: New-onset ALO was seen in 17 (9.1%) of the 187 patients after an average of 16.9 months (Range - 6-36 months). Comparison of the groups with and without ALO revealed that ALO occurred more often in older patients, both at the onset of PD symptoms and at surgery and in those with non-tremor dominant subtypes of PD and freezing of gait at baseline. The extent of levodopa dose reduction after surgery and the pre-operative severity of motor symptoms were not risk factors. Response to adjustments of dopaminergic medications and stimulation parameters was ill-sustained or nil. Botulinum toxin therapy resulted in satisfactory improvement in the majority. CONCLUSIONS: New-onset ALO is an uncommon phenomenon that manifests months after STN DBS. Development of ALO is likely to be due to the effects of chronic stimulation of basal ganglia-thalamo-cortical or brain stem circuits controlling lid movements in susceptible patients. Botulinum toxin therapy offers relatively better relief of symptoms than other strategies.

Interleaved Stimulation for Freezing of Gait in Advanced Parkinson's Disease.

BACKGROUND: Freezing of gait (FOG) is a disabling and refractory symptom of advanced Parkinson's disease (PD). Interleaved stimulation (ILS) is a novel paradigm which may benefit axial symptoms of PD. OBJECTIVES: To assess the effect of ILS on FOG in patients unresponsive to conventional subthalamic nucleus (STN) stimulation. METHODS: 19 PD patients receiving subthalamic stimulation and experiencing FOG at both conventional (130-150Hz) and low frequency (60Hz) stimulation were given ILS.The primary outcome measure was the UPDRS part III gait score (item 29) at 3 months after ILS. A subset of patients was tested with the stand-walk-sit (SWS) test, 30 min after ILS. RESULTS: The mean UPDRS part III gait score (baseline: 1.8 ± 0.6) improved at 30 min (1.1 ± 0.8, P = 0.017) and remained improved at 3 months (1.2 ± 0.8, P = 0.048). FOG episodes reduced during SWS test (P = 0.041). CONCLUSIONS: ILS of STN through two adjacent contacts provided significant short-term beneficial effects on FOG.

Subtypes of PSP and Prognosis: A Retrospective Analysis.

BACKGROUND: Progressive supranuclear palsy (PSP) is a clinically heterogeneous disease characterized by supranuclear gaze palsy and varying combinations of Parkinsonism, gait disturbances, postural instability, and fronto-limbic cognitive dysfunction. A major challenge in clinical diagnosis is the existence of subtypes whose clinical features overlap with those of other Parkinsonian disorders. OBJECTIVES: To categorize patients of PSP into its using the recently proposed movement disorder society criteria (2017) and to determine the prognosis of the PSP subtypes. METHODS: Demographic and clinical data of patients diagnosed with PSP over a 21 year period were collected by review of medical records and categorized into its subtypes. Subtype prognosis was assessed from the interval between disease onset and attainment of the first of 5 clinical disability milestones namely wheelchair dependency, unintelligible speech, severe dysphagia, severe cognitive impairment, and urinary catheterization. RESULTS: When categorized into subtypes, out of the 334 patients with PSP, PSP-RS predominated (72%), followed by PSP-parkinsonism (PSP-P) (13.5%), PSP-corticobasal syndrome (PSP-CBS) (5.1%), PSP-frontal (PSP-F) (4.2%), PSP-progressive gait freezing (PSP-PGF) (4.2%), PSP-postural instability (PSP-PI) (0.6%), and PSP-speech/language (PSP-SL) (0.3%). PSP-P reaches the milestones of wheelchair dependency, unintelligible speech, and dysphagia later than other subtypes. CONCLUSION: PSP-RS was the commonest and PSP-OM the rarest PSP subtype in our retrospective PSP cohort analysis. PSP-P had a better prognosis than all other subtypes of PSP. A large proportion of these cases would remain unclassified using NINDS-SPSP (1996) criteria.

Genetic Architecture of Parkinson's Disease in the Indian Population: Harnessing Genetic Diversity to Address Critical Gaps in Parkinson's Disease Research.

Over the past two decades, our understanding of Parkinson's disease (PD) has been gleaned from the discoveries made in familial and/or sporadic forms of PD in the Caucasian population. The transferability and the clinical utility of genetic discoveries to other ethnically diverse populations are unknown. The Indian population has been under-represented in PD research. The Genetic Architecture of PD in India (GAP-India) project aims to develop one of the largest clinical/genomic bio-bank for PD in India. Specifically, GAP-India project aims to: (1) develop a pan-Indian deeply phenotyped clinical repository of Indian PD patients; (2) perform whole-genome sequencing in 500 PD samples to catalog Indian genetic variability and to develop an Indian PD map for the scientific community; (3) perform a genome-wide association study to identify novel loci for PD and (4) develop a user-friendly web-portal to disseminate results for the scientific community. Our "hub-spoke" model follows an integrative approach to develop a pan-Indian outreach to develop a comprehensive cohort for PD research in India. The alignment of standard operating procedures for recruiting patients and collecting biospecimens with international standards ensures harmonization of data/bio-specimen collection at the beginning and also ensures stringent quality control parameters for sample processing. Data sharing and protection policies follow the guidelines established by local and national authorities.We are currently in the recruitment phase targeting recruitment of 10,200 PD patients and 10,200 healthy volunteers by the end of 2020. GAP-India project after its completion will fill a critical gap that exists in PD research and will contribute a comprehensive genetic catalog of the Indian PD population to identify novel targets for PD.

Treatable cerebellar ataxias.

Cerebellar ataxic syndrome is a heterogenous class of disorders which can result from a miscellany of causes- genetic or acquired. There are a few metabolic, immune mediated, inflammatory and hereditary causes of ataxia which can be diagnosed from the gamut of possibilities, offering great relief to the ailing patient, their family and the treating physician. A pragmatic algorithm for diagnosing treatable causes of ataxia includes a thorough clinical history, meticulous examination for associated signs and an investigative mind to clinch the diagnosis. With novel diagnostic techniques and targeted therapies, early diagnosis and treatment can lead to favourable outcomes. In this review, diseases presenting predominantly as cerebellar ataxia and are treatable by targeted therapies are discussed.