Motor cortical disinhibition during early and late recovery after stroke

Background. Functional neuroimaging studies show adaptive changes in areas adjacent and distant from the stroke. This longitudinal study assessed whether changes in cortical excitability in affected and unaffected motor areas after acute stroke correlates with functional and motor recovery. Methods. We studied 13 patients with moderate to severe hemiparesis 5 to 7 days (T1), 30 days (T2), and 90 days (T3) after acute unilateral stroke, as well as 10 healthy controls. We used paired-pulse transcranial magnetic stimulation to study intracortical inhibition and facilitation, recording from the bilateral thenar eminences. F waves were also recorded. Results. At T1, all patients showed significantly reduced intracortical inhibition in the unaffected hemisphere. At T2, in patients whose motor function recovered, intracortical inhibition in the unaffected hemisphere returned to normal. In patients with poor clinical motor recovery, abnormal disinhibition persisted in both hemispheres. At T3, in patients whose motor function progressively recovered, the abnormal disinhibition in the unaffected hemisphere decreased further, whereas in patients whose motor function remained poor, abnormal inhibition in the unaffected hemisphere persisted. No modification of F-wave latency and amplitude were found in patients and controls. Conclusions. During early days after stroke, motor cortical disinhibition involves both cerebral hemispheres. Longitudinal changes in motor disinhibition of the unaffected hemisphere may reflect the degree of clinical motor recovery.