Transcranial Magnetic Stimulation-EEG Biomarkers of Poststroke Upper-Limb Motor Function

Background: Motor evoked potentials obtained with transcranial magnetic stimulation (TMS) can provide valuable information to inform stroke neurophysiology and recovery but are difficult to obtain in all stroke survivors due to high stimulation thresholds. Objective: To determine whether transcranial magnetic stimulation evoked potentials (TEPs) evoked using a lower stimulus intensity, below that necessary for recording motor evoked potentials, could serve as a marker of poststroke upper-limb motor function and were different compared to healthy adults. Methods: Eight chronic stroke survivors (66 +/- 21 years) and 15 healthy adults (53 +/- 10 years) performed a motor function task using a customized grip-lift manipulandum. TMS was applied to the lesioned motor cortex, with TEPs recorded using simultaneous high-definition electroencephalography (EEG). Results: Stroke participants demonstrated greater hold ratio with the manipulandum. Cluster-based statistics revealed larger P30 amplitude in stroke participants, with significant clusters over frontal (P = .016) and parietal-occipital electrodes (P = .023). There was a negative correlation between the N45 peak amplitude and hold ratio in stroke participants (r = -.83, P = .02), but not controls. Conclusions: TEPs can be recorded using lower stimulus intensities in chronic stroke. The global P30 TEP response differed between stroke participants and healthy controls, with results suggesting that the TEP can be used as a biomarker of upper-limb behavior.