Sleep and epilepsy.

Over a century of work has confirmed crucial links between sleep and epilepsy. Seizures and some antiepileptic drugs (AEDs) adversely affect the continuity of sleep. However, sleep is fragmented in the absence of seizures or medication, suggesting that sleep instability may be an inherent component of certain forms of epilepsy. In turn, sleep instability can promote seizures, thus forming a vicious cycle. Sleep deprivation provokes seizures and epileptiform discharges in some people with epilepsy. Synchronized nonrapid eye movement (NREM) sleep facilitates seizures, whereas desynchronized rapid eye movement (REM) sleep discourages seizure occurrence. The sleep electroencephalogram (EEG) is useful in the diagnosis and localization of epilepsy, as new epileptic foci can appear in sleep and REM sleep may demonstrate the narrowest localization of the primary focus. Polysomnography (PSG) with expanded EEG aids in the differentiation of seizures and parasomnias and in the diagnosis of primary sleep disorders, such as sleep apnea, that can exacerbate seizures. Treating sleep apnea may lead to improved seizure control. These observations underscore the importance of sleep in the diagnosis and treatment of people with epilepsy.