ID 29 – Focal lesion on the hand knob re-localizes motor function laterally compared to the unaffected hemisphere

Abstract

Objective To evaluate the differences in cortical muscle representations between affected and unaffected hemispheres in stroke patients using navigated transcranial magnetic stimulation (nTMS). Methods Eight right-handed chronic ischemic stroke patients (2 females, age range: 48–68 years) who had an M1 hand knob localized lesion (2 left hemisphere, 6 right hemisphere, at least 2 years from stroke) were studied. Single-pulse nTMS was applied with a stimulation intensity of 110% of the resting motor threshold to map the functional cortical representation of APB muscle of affected and unaffected hemisphere. Differences in center of gravities (CoGs) obtained in cortical areas producing responses exceeding 50 μ V in amplitude were assessed using paired t-test. Results CoGs on the affected hemisphere were more lateral compared to the unaffected hemisphere (mean difference 0.9 cm, p = 0.030), no differences were observed in anterior-posterior direction ( p = 0.190). The representation areas between affected and unaffected hemisphere were not different form each other ( p = 0.577). Conclusions The cortical muscle representation of the affected hemisphere had changed, which can be seen as more laterally localized CoG compared to the unaffected hemisphere. Key message Focal lesion on the motor functional hand area causes re-localization of the representation, while the representation size is unaffected.