The positive diagnosis of narcolepsy and narcolepsy's borderland.

We studied the validity of cataplexy and number of sleep-onset rapid-eye-movement periods (SOREMPs) during one Multiple Sleep Latency Test (MSLT) as determinants of narcolepsy in 306 subjects with excessive daytime sleepiness not related to obstructive sleep apnea or other known syndromes. The subgroup defined by a history of cataplexy was the most homogeneous in clinical and polygraphic variables. However, only 83% of these subjects had two or more SOREMPs in one MSLT. The subgroup defined by two or more SOREMPs included many patients without cataplexy. A disproportionate number of these subjects were older women whose chances of developing cataplexy are remote. This group of older women had a higher number of periodic leg movements during sleep than the other groups. Patients with both cataplexy and two or more SOREMPs have the greatest chance of being DR2 DQw1 positive. Thus, the combination of history of cataplexy and two or more SOREMPs is the best clinical determinant of narcolepsy. However, two or more SOREMPs is a poorer discriminant of narcolepsy than history of cataplexy.