Cataplexy delineates a brief episode of generalized loss of muscle tone without alteration in consciousness.
When cataplexy is triggered by laughter, the term “gelastic” is utilized.
Gelastic cataplexy and vertical supranuclear gaze palsy (VSGP) are classical features of Niemann Pick type C (NPC).
Gelastic cataplexy is observed in almost 50% of all patients with NPC and may develop during the course of the disease or rarely be the presenting symptom.
Cataplexy reflects a rapid eye movement (REM)‐sleep‐related phenomenon involving multiple neurotransmitter systems which regulate sleep and postural muscle tone.
It is commonly a component of the narcoleptic syndrome alongside daytime sleepiness, sleep paralysis, and vivid hallucinations at the beginning and end of sleep.
Hypocretin excites motor neurons and helps to maintain muscle tone by activating the monoaminergic pathway.
In NPC, the accumulation of lipid‐storage products in the nervous system might affect the hypocretin‐producing cells in the hypothalamus, reducing its level