Effects of sleep and sleep stage on epileptic and nonepileptic seizures

Previous studies of patients with epilepsy and animal models of epilepsy suggest that sleep increases the frequency, duration, and secondary generalization of seizures. This information is, however, incomplete.

We retrospectively examined video-EEG monitoring reports from our comprehensive epilepsy center. We recorded seizure type, site of onset (for partial seizures), sleep state at onset, and whether partial seizures secondarily generalized. Seizures arising from sleep were then reviewed to determine sleep state.

We analyzed 1,116 seizures in 188 patients. Thirty-five percent of complex partial seizures (CPSs) starting during sleep underwent secondary generalization compared with 18% in wakefulness (p < 0.0001). Frontal lobe CPSs secondarily generalized at equal rates during sleep (22%) and wakefulness (20%), but temporal lobe CPSs generalized much more frequently during sleep (45%) than in wakefulness (19%; p < 0.0001). Frontal lobe seizures were more likely to occur during sleep (37%) than were temporal lobe seizures (26%; p = 0.0068). CPSs were more frequent in stages 1 and 2 and occurred rarely during REM. Seizures starting during slow-wave sleep were significantly longer than seizures starting during wakefulness or stage 2 sleep. Psychogenic nonepileptic seizures (PNESs) were rare between midnight and 6 a m. and never occurred during sleep.

Sleep has a pronounced effect on secondary generalization of partial seizures, especially those of temporal lobe origin. Frontal lobe seizures occur more often during sleep than do temporal lobe seizures, and occurrence during sleep helps to distinguish PNESs from CPSs.