LATERALIZATION OF THE P22 N30 COMPONENT OF SOMATOSENSORY-EVOKED POTENTIALS OF THE MEDIAN NERVE IN PATIENTS WITH CERVICAL DYSTONIA/

Somatosensory evoked potentials (SEPs) of the median nerve were record ed in 40 patients suffering from cervical dystonia and in 40 healthy v olunteers as a control. Before recording the median nerve SEPs, polymy ographic recordings were performed in all patients with cervical dysto nia. The activity of cervical muscles was recorded, and the leading mu scle of cervical dystonia was determined. Patients were divided into t wo groups according to the results of polymyography. The leading muscl e was sternocleidomastoid in the first group and the splenius capitis in the second group. Patient SEPs were recorded during abnormal head r otation. SEPs in 20 healthy Volunteers were recorded with the head in the middle position. SEPs of another 20 healthy volunteers were record ed with the head rotated 60 degrees to the right. The mean peak-to-pea k amplitude values of the precentral P22/N30 complex and the mean rati o of the P22/N30 amplitudes between both hemispheres were calculated i n the F3 (F4) and C3' (C4') electrode positions in all four groups. No significant lateralization of the precentral P22/N30 component was fo und in either group of healthy volunteers. In dystonic patients in who m the sternocleidomastoid was determined as the leading muscle of dyst onia, a statistically significant lateralization of the P22/N30 compon ent toward the ipsilateral side of the leading muscle was found. In th e group with the splenius capitis determined as the leading muscle of dystonia, a statistically significant lateralization of the P22/N30 co mponent toward the contralateral side of the leading muscle was found. The possibility that the precentral cortex is activated differently i n cervical dystonia patients who have different muscle patterns of dys tonia is discussed.