[Readiness potential associated with an athetotic movement].

A 28-year-old man was admitted to our hospital because of focal seizures probably generated by the right sensorimotor cortex with secondary generalization for 3 months. He had 5 years history of keratoconjunctivitis and iriditis. Physical examination revealed minimal hemiparesis and hyperreflexia in the left side and left papillitis. Cerebrospinal fluid analysis showed 75 cells per cubic-millimeter (all lymphocytes) and 88 mg/dl protein. Computerized tomography of the brain revealed elimination of the sulcus and vague enhancement of the cortex in the right cerebral hemisphere. The symptoms and the laboratory data improved spontaneously in a few months. Slow, athetotic movements were observed in the left forearm extensor muscles for about 10 days period. Electromyography (EMG) of these movements showed bursts of 300-800 sec in duration which repeated almost regularly at a varying frequency of 0.3-0.5 msec. The electroencephalographic (EEG) studies revealed slow background activities over the right hemisphere. The simultaneous recording of EEGs and EMGs demonstrated no EEG activity correlated with the athetotic movements. In the jerk-locked averaging (JLA) recorded with the time constant of 0.3 sec, no spiky or sharp EEG activities were detected before the EMG discharges of the left forearm extensor muscles. However, JLA with the time constant of 3.2 sec disclosed a slow negative shift which preceded the athetotic movement by about 500 msec. This negative potential was fairly localized in the right central area, which was thought to be consistent with the hand area of the motor cortex contralateral to the muscles showing the athetotic movements. The present case had a wide-spread, mainly unilateral lesion in the cerebral hemisphere.(ABSTRACT TRUNCATED AT 250 WORDS)