The Lateralization of Resting Motor Threshold to Predict Medication-Mediated Improvement in Parkinson’s Disease

Abstract

Cortical stimulation patterns in patients with Parkinson’s disease (PD) are asymmetric and get altered over time. This study examined cortical neurophysiological markers for PD and identified neurophysiological markers for lateralization in PD. We used transcranial magnetic stimulation (TMS) to study corticospinal and intracortical excitability in 21 patients with idiopathic PD. We used the Movement Disorder Society Unified Parkinson’s Disease Rating Scale for examination during on and off periods and evaluated inhibitory and facilitatory process markers using TMS, including resting motor thresholds (RMT), active motor thresholds, and motor evoked potential amplitude. The RMT in the more affected cortex was significantly shorter than in the less affected cortex, and was strongly correlated with improved motor function following medication. Patients in the tremor group exhibited significantly lower RMT compared to those in the akinetic-rigid group. Cortical electrophysiological laterality observed in patients with PD may be a useful marker for guiding treatment and identifying underlying compensatory mechanisms.

A comparative transcranial magnetic stimulation study: Assessing cortical excitability and plasticity in Alzheimer's disease, dementia with Lewy bodies and Frontotemporal dementia

“…Although this finding may indicate a glutamatergic dysfunction in the cortical neurons in DLB similar to AD, the co‐existence of cognitive findings with parkinsonism may be related to the lower rMT in our study. rMT is lower in Parkinson's disease; it is more evident on the more affected side and tremor‐dominant patients 40 . For example, patients with vascular parkinsonism with cognitive impairment also had reduced rMT and a significant reduction in SICI 41 .…”

“…rMT is lower in Parkinson's disease; it is more evident on the more affected side and tremordominant patients. 40 For example, patients with vascular parkinsonism with cognitive impairment also had reduced rMT and a significant reduction in SICI. 41 Therefore, a detailed approach regarding the subanalysis of clinical findings warrants further analysis.…”