Cataplexy with Normal Sleep Studies and Normal CSF Hypocretin: An Explanation?

Patients with narcolepsy usually develop excessive daytime sleepiness (EDS) before or coincide with the occurrence of cataplexy, with the latter most commonly associated with low cerebrospinal fluid (CSF) hypocretin-1 levels. Cataplexy preceding the development of other features of narcolepsy is a rare phenomenon. We describe a case of isolated cataplexy in the context of two non-diagnostic multiple sleep latency tests and normal CSF-hypocretin-1 levels (217 pg/mL) who gradually developed EDS and low CSF-hypocretin-1 (< 110 pg/mL).