A standardized test to document cataplexy

Cataplexy is the pathognomonic symptom of narcolepsy type 1 (NT1). Since it is considered difficult to be directly observed or documented by clinicians, its diagnosis relies mainly on history taking. Our study aimed at testing the feasibility of a standardized video recording procedure under emotional stimulation to document cataplexy in the diagnostic work-up of suspected hypersomnia of central origin.

Two-hundred-eight consecutive patients underwent the diagnostic work-up and reached the final diagnosis of NT1 (n = 133), idiopathic hypersomnia or narcolepsy type 2 (IH/NT2 group, n = 33), or subjective excessive daytime sleepiness (sEDS group, n = 42). All subjects underwent a standardized video recording procedure while watching funny movies selected according to individual preferences, and a technician blind to clinical features reviewed the recordings to identify hypotonic phenomena that were finally confirmed by patients.

The video recording under emotional stimulation captured hypotonic phenomena in 72.2%, 9.1% and 4.8% of NT1, IH/NT2, and sEDS subjects (p < 0.0001), respectively. When tested against CSF hypocretin deficiency, the documentation of a hypotonic episode at the test showed an area under the ROC curve of 0.823 ± 0.033 (p < 0.0001). NT1 patients under anticataplectic medications showed less frequently hypotonic episodes than untreated ones (48.0% vs 77.8%, p = 0.003).

A standardized video recording procedure under emotional stimulation can help in the characterization of suspected hypersomnia of central origin. Further multi-center studies are warranted to extend the present findings and integrate a shared procedure for the laboratory work-up of narcolepsy.