Electroencephalographic study on narcolepsy

Abstract

A total of 124 EEG examinations were performed in 75 narcoleptic patients. The routine EEGs were normal (abnormal slow waves being observed in less than 10%). The majority of the patients fell in drowsy state and sleep in the early part of the examination and about a half of them did so even during overbreathing. Polygraphic recording of the EEG, EKG, eye movements and respiratory movements were obtained in 34 examinations performed in 21 narcoleptics. An EEG pattern resembling that of drowsy state was found in 18 records in association with rapid eye movements (REM) at the sleep onset or several minutes after the onset. The patients often experienced sleep paralysis and/or hallucinations exclusively in the sleep onset REM period. During a cataplectic attack lasting for a brief period of about 30 sec, low voltage alpha rhythm was observed. Two other recordings obtained soon after the onset of and during cataplectic attacks which lasted several minutes indicated that the patients fell in the REM period soon after the onset of the attacks. The patients experienced hallucinations and/or dreams in the later parts of the attacks, which corresponded to the REM period. It would thus seem that cataplectic attacks are experienced in the transitional state from wakefulness to the REM period. The patients were in a similar or slightly higher level of consciousness in the early part of the sleep onset REM period than in drowsy state. In the REM period occurring several minutes after the sleep onset, they were in sleep, the depth of which corresponded to the sleep stages with spindles and high voltage slow waves. When the EEG pattern of the other sleep stages were observed, they were really in sleep, the depth of which was comparable to that of normal persons in the corresponding sleep stages. The EEG response to arousing stimuli were much decreased in the REM period as compared with those observed in the other sleep stages. In the early part of the sleep onset REM period as well as in the other part of the REM period the flash stimuli induced little or no EEG responses, although in the former period the patients were conscious of the stimuli and later recollected the correct number of them. In other sleep stages than the REM period the patients responded to and remembered only those but not all stimuli that induced marked arousal response in their EEGs. In conclusion, the basic disturbances characterizing narcoleptics are a persistent and intense inclination to fall in sleep and to fall into the REM period of sleep directly from wakefulness and at the sleep onset. Both, but predominantly the former, characterize sleep attacks, and the latter is manifested as cataplectic attacks, sleep paralysis and hypnagogic hallucinations. Narcolepsy is considered to be a disease not related to epilepsy.