Many subtle electrical abnormalities become more noticeable in the sleep deprived state. The stress of being sleep deprived also contributes to abnormal manifestations appearing. The sleep deprived patient is more likely to fall asleep during the recording , giving us an opportunity to study the arousal phase which is a time when seizures are very likely to appear. It has to be kept in mind that patients who are coming for the test sleep deprived should not be driving.