Mechanisms of hand motor recovery after stroke: An electrophysiologic study of central motor pathways

Mechanisms of motor recovery after a stroke are still poorly understood. A contribution of the healthy hemisphere has been proposed based on clinical and neuroimaging data. We report our observations from a group of patients studied serially during the first two months after stroke and another group of patients studied in the chronic phase after stroke using transcranial magnetic stimulation and the MRC scale for estimation of hand motor deficit. Among the patients studied in the acute and subacute phase (n = 16) recordable motor evoked potentials (MEPs) in the affected hand after contralateral hemispheric stimulation were present in all cases who improved their hand motor score. There was a strong correlation between MEP amplitude/latency and hand motor scores at day 60. In the patients studied in the chronic phase (n = 16), MEPs after stimulation of the affected hemisphere were observed in all patients with or without recovery, although the MEP amplitude was reduced in the four patients with no hand motor improvement, and normal in all patients with motor score improvement. There was also a significant correlation between the MEP amplitude/latency and hand motor scores. An ipsilateral response after focal stimulation of the intact hemisphere was only observed in one case (who did not recover). Our data do not suggest a significant participation of the intact hemisphere or of corticoreticulospinal pathways in motor recovery after stroke. Conversely, the persistence of a functional pyramidal tract seems necessary for recovery to occur after a cortical stroke.