Comparative evaluation of sleep deprivation and sedated sleep EEGs as diagnostic aids in epilepsy

The comparative value of sedated sleep and sleep deprivation EEGs was investigated in a consecutive series of 43 patients who had received both types of activation study for diagnostic purposes. Patients were referred because of persisting doubt concerning either the diagnosis of epilepsy, or the type of epilepsy present in those with definite seizures. Forty-one had had routine waking EEGs, all of which were normal or only mildly abnormal. EEGs were rated without access to previous reports or clinical data, and epileptiform discharges (ED) were semiquantified during wakefulness and sleep. De novo precipitation of ED, increase in abundance of ED and discovery of a new independent focus or a new type of ED were taken as the yield of useful information. 44% of sleep deprivation records provided useful information compared to 14% of sedated sleep recordings (P < 0.005). In addition, sleep deprivation was significantly superior to sedated sleep in differentiating those with a final clinical diagnosis of epilepsy from those with doubtful or no epilepsy (P < 0.001). It is suggested that the usefulness of the interictal EEG in patients with uncertain epilepsy or epilepsy of unknown type is increased by performance of a diagnostic series to include routine waking, sedated sleep and sleep deprivation recordings.