Neurophysiological studies of myoclonus epilepsy

In 7 patients with myoclonus epilepsy (toxic encephalopathy - 1, postanoxic encephalopathy - I, MELAS - 1, MEERF-syndrome - 2, Jantz syndrome - I, Unferricht-Lundborg myoclonus epilepsy - 1) EEG, EP and movement-related brain potential (MRBP) were studied. In EEG there were spike discharges related to myoclonia and high photosensitivity. The "giant" EPs were formed of early components corresponding to primary cortical input. Epileptiform MRBPs related to myoclonia coincided in parameters with giant SSEP. Spindles of sharp rhythmic activity 16-18 Hz in EEG coincided with the flicker frequency optimum for photoparoxismal response and the period of spike discharges in the wave form of the VEP. The data suggest that epileptic myoclonus is caused by hyperexcitability of cortical neurones related to excitability cycles and leading to hypersynchronous discharges on exogenic or endogenic afferent input.