Negative myoclonus in Creutzfeldt-Jakob disease

Objective: To describe electrophysiological findings in a patient with Creu tzfeldt-Jakob disease (CTD) showing negative myoclonus. Methods and results: We studied this CJD patient electrophysiologically, in comparison with two patients with cortical reflex positive myoclonus due t o benign adult familial myoclonic epilepsy (BAFME). Spontaneous negative my oclonus was associated with periodic synchronous discharges (PSDs) on the e lectroencephalogram, but negative myoclonus could also be induced by electr ical stimulation of the median nerve in the CJD patient. This patient showe d giant somatosensory evoked potentials (SEPs) and enhanced C reflexes, and the duration of the induced EMG silences was found to be significantly cor related with the amplitude of cortical SEPs. The duration of silent periods (SPs) produced by magnetic stimulation of the motor cortex was extremely l ong. The study of recovery function of SEPs suggested that the excitability of the somatosensory cortex was decreased during a long post-stimulus peri od. These findings were clearly different from those of patients with BAFME . Conclusions: This CJD patient had two types of negative myoclonus; one was associated with PSDs and the other was cortical reflex negative myoclonus. The long-lasting decrease in excitability of the sensorimotor cortices afte r stimulation could be related to the occurrence of both types of negative myoclonus. (C) 2000 Elsevier Science Ireland Ltd. All rights reserved.