The clinical features of cataplexy: a questionnaire study in narcolepsy patients with and without hypocretin-1 deficiency.

Background: Narcolepsy is often not recognized or accurately diagnosed. This may be due to the fact that cataplexy, a core symptom which is virtually 100% specific, can-in practice-only be diagnosed based on the patient's history. However, the current definition of cataplexy is not very precise and the common distinction between "typical" and "atypical" cataplexy is not well codified.

Methods: We aimed to provide a detailed description of the phenotypic variability of cataplexy. We included 109 patients with a definite history of cataplexy and a proven hypocretin-1 deficiency. The questionnaire contained 37 items to broadly cover the clinical aspects of cataplexy, including triggers, pattern and duration of muscle weakness, associated aspects such as sensory phenomena, and limitations in daily life due to cataplexy.

Results: "Laughing" only listed in place 11th of most frequent triggers. "Laughing excitedly" was much more potent, showing that a certain intensity of the emotion is important for a "cataplectogenic" effect. Anger was the highest ranking "non-humorous" trigger, followed by "unexpectedly meeting someone well known." About 60% of patients also had spontaneous cataplectic attacks. Forty-five percent of patients experienced both partial and complete attacks and 30% only partial cataplexy. Fifteen percent of complete attacks were reported to last longer than 2 min. An abrupt return of muscle function was an important feature. The jaw and the face were most often involved in partial attacks, even more than the knee or the leg.

Conclusions: Cataplexy presents with a large phenotypical diversity, so the current "typical" versus "atypical" distinction may be difficult to hold. We propose that grading cataplexy with different levels of diagnostic confidence may be more useful.