Could the Early Disinhibition of the Unaffected Motor Cortex Predict Motor Recovery After Stroke?

BACKGROUND: Whether intracortical inhibition in the unaffected hemisphere is related to motor recovery after stroke may depend on the status of corticospinal excitability in the affected hemisphere. The aims are (1) to identify the presence of short-latency intracortical inhibition (SICI) in the acute phase according to the motor-evoked potential (MEP) status of the patients and (2) to investigate whether unaffected hemisphere SICI is associated with motor recovery at 3 months in subgroups of patients (with or without an MEP). METHODS: We enrolled 95 patients with stroke (median age, 68 years; interquartile range, 61–78 years, sex: 61% males, n=58) with upper extremity weakness persistent on day 3 and analyzed 83 patients (median age, 67 years; interquartile range, 59–77 years, sex: 65% males, n=54) in this single-center study (from August 2022 to May 2024). Transcranial magnetic stimulation was performed before day 7 to determine the presence of MEP and to record SICI in both hemispheres. The motor evaluation was performed on day 7 using the Fugl-Meyer Assessment of the Upper Extremity and at 3 months by the Fugl-Meyer Assessment of the Upper Extremity and the Action Research Arm Test. RESULTS: SICI was present in the unaffected hemisphere in 58% of MEP− patients (patients with no evocable MEP in the first dorsal interosseous; n=14/24) and 57% of MEP+ patients (patients with evocable MEP in the first dorsal interosseous; n=33/57, 2 missing data). The presence of SICI in the unaffected hemisphere in MEP− patients (but not in MEP+) was associated with better motor recovery (Spearman rank coefficient, −0.514 [95% CI, −0.774 to −0.106]; P =0.017) and was an independent predictor of motor recovery on a stepwise multiple linear regression, along with the Fugl-Meyer Assessment of the Upper Extremity at day 7 ( R ²=54%, P =0.002). CONCLUSIONS: Implementing intracortical inhibition could improve prediction models in future studies for severe patients without an MEP whose recovery trajectories are hard to predict and for whom clinical rehabilitation decisions are difficult to make.