MEP Status is Not Predictive of Response to Upper Limb Training in People With Chronic, Moderate–Severe Hemiparesis Post-Stroke

Background: The presence or absence of a motor evoked potential (MEP) in the post-stroke hemiparetic limb has been recommended by rehabilitation experts as a predictive biomarker which is ready for use in clinical trials. However, evidence remains limited for its prognostic value in the chronic stage. Objective: Determine if MEP status (MEP+ or MEP−) obtained within 1 week of starting treatment (baseline) predicts the magnitude of response to intervention in individuals with chronic, moderate–severe hemiparesis. Methods: This is a retrospective analysis using data from a single-blind randomized controlled trial. Seventy-six individuals ≥6 months post-stroke with a baseline Fugl-Meyer Assessment of the Upper Extremity (FMUE) score of 23 to 40 underwent 30 hours of upper limb (UL) training over 6 weeks. Participants were stratified by baseline MEP status. The primary endpoint was change in FMUE score from baseline to post-test. Results: Seventy-three participants provided FMUE scores and MEP status at baseline. Individuals who were MEP+ (n = 49) demonstrated a mean FMUE change score of 5.09 (standard deviation [SD] = 3.8) while MEP− (n = 24) individuals demonstrated a mean change score of 5.04 (SD = 4.0). There were no significant differences between the groups (mean difference = 0.05, P =.96, 95% confidence interval [−1.99, 2.09]). Conclusions: Our results demonstrate that MEP status at the start of an intervention in the chronic stage does not predict recovery for people with moderate–severe UL impairments. This finding directly challenges recent expert recommendations to stratify trial groups by MEP status, suggesting that such stratification may not effectively reduce variability or predict treatment response at the chronic stage. Clinical Trial Registration: ClinicalTrials.gov, ID: NCT03517657.