Abstract WMP37: Differential Montage Effect On Cortical Excitability In Ischemic Stroke Patients By Single Session Of High Amperage Transcranial Direct Current Stimulation

Abstract

Background and Objective: We aim to assess the cortical excitability under three montages with single session of transcranial direct current stimulation (tDCS) at 4 mA on ischemic stroke patients. Methods: Adult subjects with first-ever unilateral ischemic stroke ≥6 months and inducible motor evoked potentials (MEP) underwent 3 sessions (washed out ≥2 days apart) of 30 minutes 4 mA tDCS in anodal, cathodal or bihemispheric montage (in pseudorandom order) combined with t upper extremity repetitive task training administered by an Occupational Therapist. We collected MEP responses to transcranial magnetic stimulation (TMS) single pulse, short intracortical inhibition (SICI, 3 ms) and intracortical facilitation (ICF, 15 ms) on bilateral abductor pollicis brevis (APB) muscles at baseline and four post-stimulation timepoints 12 minutes apart. We also monitored safety by recording adverse events, surveying subjects with a questionnaire on tolerability issues and collecting biometric measures (body resistance, skin temperature under the tDCS electrode). Results: Eighteen subjects completed 54 tDCS sessions in total. We observed montage ( P <0.0001) and time ( P <0.01) effects only on the lesioned hemisphere, with bihemispheric tDCS showing relatively higher peak-to-peak MEP. Lack of montage effect in baseline ( P >0.949) suggested sufficient washout interval across the visits. No subjects experienced any adverse events. Biometric measures and tolerability were comparable across the three montages. The most common tolerability issue was transient redness under the tDCS electrodes (70% at anode, 48% at cathode). Conclusions: The bihemispheric montage increased ipsilateral cortical excitability the most in a single session of 4 mA tDCS in chronic ischemic stroke patients. Additionally, a current level of 4 mA is safe and tolerable over multiple sessions.