NEUROPHYSIOLOGICAL FINDINGS IN THE NORTHERN EPILEPSY SYNDROME

We describe the neurophysiological findings in the northern epilepsy s yndrome (NES), an autosomal recessively inherited childhood onset epil epsy with associated mental deterioration. Sixty-five EEGs of 18 patie nts (10 females and 8 males) from the age of 5 years to 52 years were analyzed. EEG showed relatively slight changes at the outbreak of epil epsy at the mean age of 6.6 years (range 5-10 years). Slowing of the b ackground activity to 6-7 Hz theta activity, abundant diffuse or inter mittent theta and delta activity and disappearance of sleep-specific a ctivity characterized the EEGs at puberty. The amount of diffuse delta and theta activity diminished in adulthood. Epileptiform findings wer e scanty. Spikes and sharp waves occurred in 43% of the recordings wit h varying localization, form and extent. Intermittent 2-4 Hz sharp and slow wave rhythm was seen in 32% of the recordings. Of the three icta l recordings, one showed a primarily generalized discharge pattern, wh ile two were clearly asymmetric. Clonazepam was the most effective ant iepileptic drug, and it also normalized the EEG when started in childh ood or at the onset of puberty. Visual evoked potentials were abnormal in 44% and brainstem auditory evoked potentials in 35%. The neurophys iological findings suggest an extensive, probably multifocal degenerat ive brain process, which reaches its peak at puberty. Although the abn ormal features of EEG often decreased in adulthood, the clinical cours e of NES showed slow progression throughout the lifetime.