Patterns of motor control reorganization in a patient with mirror movements

Objective: To explore motor control reorganization in a 40-year-old, left-h anded patient with perinatally acquired mirror movements. Methods: We performed simultaneous bilateral recordings of motor evoked pot entials (MEPs) following focal transcranial magnetic stimulation (fTMS) and of central silent period (cSP) during unilateral voluntary contraction in abductor pollicis brevis (APB) and abductor digiti minimi (ADM) muscles. Results: For both muscles the MEP study showed bilateral fast-conducting co rticospinal projections front the right undamaged hemisphere, and residual contralateral projections from the left hemisphere. The cSP findings differ ed in the two Muscles: the mirror phenomenon was bilateral in the ADM, but present only on the right side in the APB muscles; the mirror activity of r ight ADM and APB muscles was inhibited only by fTMS of the ipsilateral righ t motor cortex; the mirror phenomenon in the left ADM muscle was inhibited only by fTMS of the contralateral right motor cortex. Conclusions: Mirror movements of right APB and ADM muscles were sustained b y the ipsilateral connections from the undamaged motor cortex, while the mi rror phenomenon in the left ADM, muscle could be explained by hypothesizing a bilateral activation of motor cortices. This previously unreported elect rophysiological picture demonstrates that different patterns of motor contr ol may realize after perinatal cerebral lesions, even in different distal m uscles of the same patient. (C) 2000 Elsevier Science Ireland Ltd, All righ ts reserved.