Decreased cerebrospinal fluid hypocretin-1 levels near the onset of narcolepsy in 2 prepubertal children.

We present 2 cases of narcolepsy with prepubertal onset. Although excessive daytime sleepiness and cataplexy had appeared early in both patients, the presence of sleep-onset rapid eye movement periods was detected several months after the onset of hypersomnia. The levels of hypocretin in the cerebrospinal fluid were reduced when measured 3 weeks (Patient 1) and 2 months (Patient 2) after the appearance of hypersomnia, before the presence of sleep-onset rapid eye movement periods was confirmed. Because the symptoms of narcolepsy in children are often obscure and easily mistaken as other diseases, and the electrophysiologic studies may not be specific in the early stage, the definite diagnosis tends to be delayed. Measurement of hypocretin-1 levels in the cerebrospinal fluid is useful for the early diagnosis of narcolepsy with prepubertal onset.