Sleep deprivation as a method of EEG activation. Observation on the incidence of positive responses

Sleep deprivation is known to be one of the principal mechanisms to activate epileptogenic activity in the EEG recording and indeed it is one of the most common activation techniques in EEG practice. It is generally recognized that about one third of patients with seizures presenting a normal or borderline normal routine EEG may be expected to exhibit an abnormal paroxysmal recording after sleep deprivation. In the present study it was estimated that activation, by sleep deprivation, of a normal EEG into a record with abnormal paroxysmal activity, may be expected to be even higher with selection of patient population. The incidence of such activation was found to be 23% among patients presenting a history of attacks with variable clinical paroxysmal manifestations with or without impairment of consciousness, but in whom the overall picture could not be judged typically epileptic upon historical grounds alone. However, the incidence of activation was found to increase up to 57% among patients with attacks judged by history to be typical as to their epileptic nature. This higher incidence of activation appears to parallel the higher incidence of underlying abnormality as revealed by CAT scanning.