Narcolepsy, also known as Gelineau syndrome, named after the French physician (1828-1906) who described it for the first time, is a sleep disorder characterised by daytime sleepiness and an uncontrollable compulsion to sleep.
The clinical picture may include other symptoms:
Cataplexy attacks, or the sudden and momentary loss of muscle tone (often associated with strong emotion), are characteristic of type I narcolepsy
Hallucinations essentially occurring on falling asleep, sleep paralysis
The inability to move or speak for a few seconds or minutes on falling asleep or waking up,
A tendency towards obesity
Narcolepsy is a rare disease that affects one in 2,500 people in Europe. It generally arises in adolescence, but a large proportion of patients remain undiagnosed and thus untreated, despite the very disabling nature of the disease.
In the first instance, its diagnosis is based on an assessment of sleepiness, often measured using the Epworth sleepiness scale, and, in the case of type I narcolepsy, the very revealing presence of cataplexy attacks.
Type I narcolepsy is the most common form, and it appears to be brought on by the destruction (often in childhood) of a group of hypothalamic neurons that secrete a small stimulating peptide called hypocretin or orexin.
Several tests allow the diagnosis to be confirmed: polysomnography (a recording of the phases of sleep), which shows abnormal direct transitions from wakefulness to paradoxical sleep, the multiple sleep latency test (MSLT) which finds a mean sleep latency of less than 8 minutes, or even cerebrospinal fluid analysis, which may find low orexin levels.
Narcolepsy is a sleep disorder in which the borderline between wakefulness and paradoxical sleep is abnormal.
Paradoxical sleep is a sleep phase discovered by Michel Jouvet in 1959, which is characterised by a loss of muscle tone, that is, a complete relaxation of muscles and numerous intense dreams.
Over the course of a physiological night’s sleep, paradoxical sleep is generally preceded by slow light sleep or deep sleep. Patients suffering from narcolepsy fall directly into paradoxical sleep without transitioning through slow sleep.