Short-Latency Afferent Inhibition Correlates with Stage of Disease in Parkinson's Patients.

BACKGROUND: Sensory-motor decoupling at the cortical level involving cholinergic circuitry has also been reported in Parkinson's Disease (PD). Short-latency afferent inhibition (SAI) is a transcranial magnetic stimulation (TMS) paradigm that has been used previously to probe cortical cholinergic circuits in well-characterised subgroups of patients with PD. In the current study, we compared SAI in a cohort of PD patients at various stages of disease and explored correlations between SAI and various clinical measures of disease severity. METHODS: The modified Hoehn and Yahr (H&Y) scale was used to stage disease in 22 patients with PD. Motor and cognitive function were assessed using the MDS-UPDRS (Movement Disorder Society-sponsored revision of the Unified Parkinson's Disease Rating Scale) part III and MoCA (Montreal Cognitive Assessment) score, respectively. Objective gait assessment was performed using an electronic walkway (GAITRite®). SAI was measured as the average percentage inhibition of test motor-evoked potentials (MEPs) conditioned by electrical stimulation of the contralateral median nerve at the wrist. RESULTS: SAI was significantly reduced in patients with advanced PD (H&Y stage 3) compared to early PD patients (H&Y stage 1) on pairwise comparison. The visuospatial executive function and orientation domains of cognition demonstrated significant negative associations with SAI. CONCLUSION: Cortical sensory-motor integration is progressively diminished as disease progresses. The observation that a reduction in SAI is associated with a reduction in cognitive function possibly reflects the progressive involvement of cortical cholinergic circuits in PD with increasing motor stage. Future longitudinal studies are necessary to confirm this preliminary result.

Comparing Stop Signal Reaction Times in Alzheimer's and Parkinson's Disease.

BACKGROUND: To investigate the relative contributions of cerebral cortex and basal ganglia to movement stopping, we tested the optimum combination Stop Signal Reaction Time (ocSSRT) and median visual reaction time (RT) in patients with Alzheimer's disease (AD) and Parkinson's disease (PD) and compared values with data from healthy controls. METHODS: Thirty-five PD patients, 22 AD patients, and 29 healthy controls were recruited to this study. RT and ocSSRT were measured using a hand-held battery-operated electronic box through a stop signal paradigm. RESULT: The mean ocSSRT was found to be 309 ms, 368 ms, and 265 ms in AD, PD, and healthy controls, respectively, and significantly prolonged in PD compared to healthy controls (p = 0.001). The ocSSRT but not RT could separate AD from PD patients (p = 0.022). CONCLUSION: Our data suggest that subcortical networks encompassing dopaminergic pathways in the basal ganglia play a more important role than cortical networks in movement-stopping. Combining ocSSRT with other putative indices or biomarkers of AD (and other dementias) could increase the accuracy of early diagnosis.

Spectrum of hospitalized NeuroCOVID diagnoses from a tertiary care neurology centre in Eastern India.

PURPOSE: To describe the spectrum of hospitalized NeuroCOVID on admission in a tertiary neurology centre in Kolkata, the largest and most populated metropolitan city in Eastern India. METHOD: We retrospectively studied confirmed COVID-19 patients admitted with a neurological condition from 1st May 2020 to 30th January 2021. Neurological diagnoses and their temporal relationship to respiratory features along with clinicodemographic profile for such patients was ascertained. RESULT: 228 patients were diagnosed with NeuroCOVID at our centre. Of the 162 included population (median age was 59 (50-70) and 62.3% (101) were male) and 73.5% were diagnosed with NeuroCovid before any respiratory or febrile features. 46 patients (28.8%) had a pre/co-existing neurological illness, and 103 (63.6%) had systemic comorbidities. No significant difference was observed when comparing demographics and comorbidities of NeuroCOVID patients presenting with and without fever and respiratory features. Moreover, no individual NeuroCOVID diagnosis was more prone to present with respiratory or febrile features. Diabetes mellitus was the only comorbidity which was significantly higher in the ischemic stroke group, all other comorbidities and characteristics were evenly distributed between stroke and non-stroke NeuroCOVID patients and encephalopathy non encephalopathy NeuroCOVID patients. CONCLUSION: Stroke and encephalopathy are the most prevalent parainfectious neurological conditions occurring with COVID-19 in the Indian population. This study demonstrates seemingly low-risk individuals (i.e. people without pre-existing systemic and neurological comorbidities) may develop neurological conditions. Moreover, NeuroCOVID may manifest independent of respiratory features and fever.

A longitudinal quantitative analysis of gait in patients with SCA-12.

INTRODUCTION: Spinocerebellar ataxia type 12 (SCA 12) is characterized by late onset tremor, ataxia and pyramidal signs. Parkinsonism and cognitive decline may appear with time. It is considered as slowly progressive but temporal evolution of symptoms has not been reported. METHOD: We report the evolution of symptoms in three SCA12 patients followed over a range of 5-6 years. We focused on the evolution of gait abnormality as it becomes the most disabling symptom as disease advances. Two-dimensional gait parameters were studied using an electronic walkway at various time points to measure objective changes in gait. RESULT: All patients presented with tremor in the upper extremity at baseline which progressed non-uniformly over the years. Progression of gait variability measures of step length, stance time and step time were also observed. CONCLUSION: Gait characteristics such as variability may precede clinical gait abnormality and could serve as a sensitive marker for disease progression for better therapeutic intervention in disease management. Future studies with larger sample size should be undertaken to conclusively validate this observation.

Task-dependent modulation of corticospinal excitability and inhibition following strength training.

This study determined whether there are task-dependent differences in cortical excitability following different types of strength training. Transcranial magnetic stimulation (TMS) measured corticospinal excitability (CSE) and intracortical inhibition (ICI) of the biceps brachii muscle in 42 healthy subjects that were randomised to either paced-strength-training (PST, n = 11), self-paced strength-training (SPST, n = 11), isometric strength-training (IST, n = 10) or to a control group (n = 10). Single-pulse and paired-pulse TMS were applied prior to and following 4-weeks of strength-training. PST increased CSE compared to SPST, IST and the control group (all P < 0.05). ICI was only reduced (60%) following PST. Dynamic strength increased by 18 and 25% following PST and SPST, whilst isometric strength increased by 20% following IST. There were no associations between the behavioural outcome measures and the change in CSE and ICI. The corticospinal responses to strength-training are task-dependent, which is a new finding. Strength-training that is performed slowly could promote use-dependent plasticity in populations with reduced volitional drive, such as during periods of limb immobilization, musculoskeletal injury or stroke.

Determining the Sites of Neural Adaptations to Resistance Training: A Systematic Review and Meta-analysis.

BACKGROUND: Resistance-training causes changes in the central nervous system (CNS); however, the sites of these adaptations remain unclear. OBJECTIVE: To determine sites of neural adaptation to resistance-training by conducting a systematic review and meta-analysis on the cortical and subcortical responses to resistance-training. METHODS: Evidence from randomized controlled trials (RCTs) that focused on neural adaptations to resistance-training was pooled to assess effect estimates for changes in strength, cortical, and subcortical adaptations. RESULTS: The magnitude of strength gain in 30 RCTs (n = 623) reported a standardised mean difference (SMD) of 0.67 (95% CI 0.41, 0.94; P < 0.001) that measured at least one cortical/subcortical neural adaptation which included: motor-evoked potentials (MEP; 19 studies); silent period (SP; 7 studies); short-interval intracortical inhibition (SICI; 7 studies); cervicomedullary evoked potentials (CMEP; 1 study); transcranial magnetic stimulation voluntary activation (VATMS; 2 studies); H-reflex (10 studies); and V-wave amplitudes (5 studies). The MEP amplitude during voluntary contraction was greater following resistance-training (SMD 0.55; 95% CI 0.27, 0.84; P < 0.001, n = 271), but remained unchanged during rest (SMD 0.49; 95% CI -0.68, 1.66; P = 0.41, n = 114). Both SP (SMD 0.65; 95% CI 0.29, 1.01; P < 0.001, n = 184) and active SICI (SMD 0.68; 95% CI 0.14, 1.23; P = 0.01, n = 102) decreased, but resting SICI remained unchanged (SMD 0.26; 95% CI - 0.29, 0.81; P = 0.35, n = 52). Resistance-training improved neural drive as measured by V-wave amplitude (SMD 0.62; 95% CI 0.14, 1.10; P = 0.01, n = 101), but H-reflex at rest (SMD 0.16; 95% CI - 0.36, 0.68; P = 0.56; n = 57), during contraction (SMD 0.15; 95% CI - 0.18, 0.48; P = 0.38, n = 142) and VATMS (MD 1.41; 95% CI - 4.37, 7.20; P = 0.63, n = 44) remained unchanged. CONCLUSION: There are subtle neural adaptations following resistance-training involving both cortical and subcortical adaptations that act to increase motoneurone activation and likely contribute to the training-related increase in muscle strength.