Paroxysmal kinesigenic choreoathetosis and abnormal contingent negative variation. A case report.

We treated a patient suffering from paroxysmal kinesigenic choreoathetosis (PKC). The etiology and pathophysiologic mechanism of this rare movement disorder are unclear. Like other patients with PKC, our patient experienced attacks more frequently when making anticipated movements. Because anticipation plays an important role in the genesis of the contingent negative variation (CNV), we investigated the CNV in our patient. One of the components of the CNV, the slow negative wave (SNW), repeatedly showed a remarkable enhancement compared with that of controls. After institution of phenytoin sodium therapy, the attacks of PKC subsided and the SNW amplitude came within the range of control values. There may be a relationship between PKC and the abnormal CNV.