Investigations on the mechanism of nocturnal epilepsy

Sixty polygraphic all-night sleep tracings were obtained, including 40 from 20 patients with epileptic attacks occurring during sleep (during treatment with anticonvulsants and after their withdrawal), and 10 tracings in each of two groups serving as controls: a group of patients with seizures occurring in the waking state and a group of healthy controls. A significant difference was observed in the sleep pattern of the patients with nocturnal attacks (who were good sleepers and received no anticonvulsants) and healthy controls. These patients had a significantly higher proportion of III + IV stages of the slow-wave sleep phase. Besides that, in all epileptics disruption and lability of the REM phase was observed, without a statistically significant reduction in the proportion of its duration during the whole sleep. Clinical seizures developed usually in the SW phase but one seizure occurred during the REM phase. The effects of anticonvulsants on sleep EEG tracings require further investigation. A significant difference was observed in the morphology and dynamics of EEG changes in both groups of epileptics. The patients with nocturnal attacks had much more frequently normal tracings in the waking state. During sleep focal changes were often found. Seizure activity of the spike-wave type was less frequent than in patients with waking attacks and the dynamics of this activity were different. It seems possible that the pathways of spread of epileptic discharges are different in these two groups of epileptics.