A standardized test for cataplexy

Abstract 

This study developed a standardized procedure for provoking cataplexy, which facilitated observation of the physiologic changes occurring with cataplexy. Data were obtained from narcoleptic patients recruited from a sleep disorder center. Patients were asked to describe the nature and frequency of cataplexy, as well as their typical emotional triggers. Referring clinicians were asked to assess the likelihood, frequency, and severity of the patients’ cataplexy. Nine patients with multiple sleep latency test (MSLT)-confirmed narcolepsy were included in this study. The subjects were then instructed to view a humorous videotape while monitored with video-polysomnography including EEG, EMG, and EOG. In the event of a spell, quadriceps reflexes were tested. The data were examined to determine the occurrence of cataplexy in response to a standardized stimuli. Cataplexy was successfully provoked in five patients (four women and one man). Areflexia of the quadriceps muscle was the most sensitive marker of a cataplectic event. EMG tone was mildly reduced in three patients with no other remarkable changes on polysomnography. The narcoleptic patients’ responses to the humorous videotapes and other stimuli varied tremendously. This pilot study demostrates the feasibility of a standardized procedure for provoking cataplexy, which permits further study of these phenomena. Furthermore, a cataplexy test has considerable potential as a diagnostic tool, especially in situations where an MSLT is impractical.

Keywords:  Cataplexy, Narcolepsy, Polysomnography, REM sleep, Sleep, Multiple sleep latency test