POSTSTROKE REORGANIZATION OF BRAIN MOTOR OUTPUT TO THE HAND - A 2-4 MONTH FOLLOW-UP WITH FOCAL MAGNETIC TRANSCRANIAL STIMULATION

Focal transcranial magnetic stimulation (TCS) was employed for the rep resentation of the motor cortex in a population of 18 patients to inve stigate the functional properties of hand motor areas 2-4 months after a monohemispheric stroke. Eleven sites were stimulated to elicit moto r evoked potentials (MEPs) in abductor digiti minimi muscle after TCS of affected (AH) and unaffected (UH) hemispheres; recording sessions w ere performed al the beginning (T1) and after 8-10 weeks (T2) of neuro rehabilitation. Barthel index and Canadian neurological scale scores w ere evaluated. A group of 20 healthy control subjects was enrolled. In stroke patients the AH was less excitable than normal, combined with a decrease in motor cortical output area (P < 0.05) in T1. In T2, ther e was an enlargement of the: hand motor area on the AH combined with a n improvement of clinical scores (P < 0.001). In T1 and T2, the amplit ude of MEPs in the AH was reduced (P < 0.001) with a prolongation of c entral conduction time (P < 0.001) and with a tendency towards improve ment in T2; the amplitude of contracted MEPs was larger than normal in the UH in T1. Both in T1 and T2, anomalous 'hot spot' (most excitable ) scalp sites, never seen in normals, were often encountered (T2 > T1) on the AH and UH. Interhemispheric differences for topography and lat ency of MEPs were remarkably affected, Our data are consistent with a rearrangement of the brain motor cortical output between 2 and 4 month s following stroke. The amelioration of the neurophysiological paramet ers was correlated with clinical improvement in disability and neurolo gical scores. This study confirms the existence in adults of brain 'pl asticity' still operating between 2 and 4 months from an acute vascula r monohemispheric insult. (C) 1997 Elsevier Science Ireland Ltd.