Sleep and epileptic activity.

Thirteen patients suffering from severe partial epilepsy and potential candidates for surgical treatment were investigated with stereotactically implanted intracerebral electrodes during nocturnal physiological sleep. The recorded electrocerebral activity was automatically analyzed to gain information on interictal epileptic events during wakefulness and the phases of sleep. The interictal epileptic activity shows: (1) great variability in the different subjects, and intra-individually, variability according to the explored cerebral regions; (2) is not influenced by the location of the recorded epileptic events; and (3) is affected by the local level of epileptogenicity. The latter was determined by the assessment of the capacity to give origin to ictal discharges and the disappearance of seizures following surgical removal. The interictal rate of spiking from the most epileptogenic cerebral zone is characterized by a relative stability during the night and by a relatively high degree during REM sleep.