Narcolepsy, from Greek words meaning numbness and attack, is often played for laughs on screen, but this episode lays out its clinical reality. The classic tetrad is excessive daytime sleepiness, cataplexy, sleep paralysis and hallucinations at the edges of sleep, though only about 20 to 25 percent of patients have all four. Cataplexy is a sudden loss of muscle tone, from a drooping jaw to a full collapse, triggered mostly by laughter and other strong emotions while the person stays fully conscious. Nights are fragmented too, since a narcoleptic brain can drop into REM sleep within five to ten minutes instead of about 90.

In type 1 narcolepsy, roughly 70,000 neurons in the lateral hypothalamus that make orexin, also called hypocretin, are lost, leaving the brain’s flip flop switch between sleep and waking unstable. The leading theory is autoimmune: people carrying the HLA DQB1*06:02 variant may lose those cells after exposure to the 2009 H1N1 influenza virus or the Pandemrix vaccine, through molecular mimicry. The episode covers the diagnostic gap of 10 to 15 years, sleep studies and spinal fluid tests, treatments from scheduled naps and stimulants to sodium oxybate at night, and research in narcoleptic dogs and mice aimed at replacing orexin signaling.

• Orexin in spinal fluid below 110 picograms per milliliter, and undetectable in up to 95 percent of type 1 cases
• Misdiagnoses as depression, epilepsy, laziness or drug use while symptoms begin in adolescence
• The multiple sleep latency test, where REM within minutes across several naps signals the disorder
• Why a 120 minute scheduled nap helps while a 15 minute power nap does little
• Doberman Pinschers and Labrador Retrievers whose spontaneous cataplexy helped find the orexin receptor genes