ABSTRACT
This chapter outlines the status of nocturnal polysomnography, the multiple sleep latency test (MSLT) and the maintenance of wakefulness test (MWT) in the evaluation and management of Narcolepsy. Much of the material discussed comes from the author’s participation in the work of a task force appointed by The American Academy of Sleep Medicine. The taskforce concluded that nocturnal polysomnography is useful in the evaluation of patients for possible narcolepsy to assess for the presence and degree of other sleep disorders such as sleep apnea. In healthy controls and narcolepsy patients, mean sleep latency (MSL) on the MSLT and the MWT is sensitive to conditions expected to increase sleepiness. However, large between subject variance in MSL makes it difficult to establish a specific threshold value for excessive sleepiness or to discriminate patients with sleep disorders from nonpatients. Sleep latencies can detect change from initial testing to subsequent testing following treatment or manipulations intended to alter sleepiness or alertness. The presence of two or more sleep onset REM periods (SOREMPs) on the MSLT is a common finding in narcolepsy patients. But, SOREMPs are not exclusive to narcolepsy patients. They are found in other conditions such as untreated sleep apnea. The MSL is sensitive to circadian changes but a relationship between MSL and evaluation of safety in real life operations has not been established. A diagnosis of narcolepsy should be made cautiously and with complete clinical information. It may be necessary to go beyond electrophysiological approaches, to develop clinical laboratory tests for biomarkers in bodily fluids or other types of specimens.
