CRITICAL REORGANIZATION IN PATIENTS WITH FACIAL PALSY

Possible changes in the organization of the cortex in patients with fa cial palsy, serving as a model of peripheral motor deefferentation, we re investigated by using transcranial magnetic stimulation (TMS) and p ositron emission tomography (PET). With TMS, the size of the area prod ucing muscle-evoked potentials (MEPs) of the abductor pollicis brevis muscle, the sum of MEP amplitudes within this area, and the volume ove r the mapping area were compared between both hemispheres in 8 patient s. With PET, increases in regional cerebral blood flow, measured with the standard (H2O2)-O-15 bolus injection technique, were compared betw een 6 patients and 6 healthy volunteers during sequential finger oppos ition. Patients moved the hand ipsilateral to the facial palsy, the co ntrol subjects the right hand. Of 9 patients in total, 5 participated in both experiments. With both methods, an enlargement of the hand fie ld contralateral to the facial palsy was found, extending in a lateral direction, into the site of the presumed face area. The PET data show ed that the enlargement of the hand field in the somatosensory cortex (SMC) is part of a widespread cortical reorganization, including the i psilateral SMC and bilateral secondary motor and sensory areas. We rep ort for the first time, using two different noninvasive methods, that peripheral, mere motor deefferentation is a sufficient stimulus for re organizational changes in the healthy adult human cortex.