Katapleksi

Katapleksi is a medical term describing a sudden, transient episode of bilateral loss of muscle tone, often with preserved consciousness, triggered by strong emotions such as laughter, anger, or surprise. Episodes typically last from a few seconds to a couple of minutes and may cause facial droop, buckling knees, or difficulty speaking. Individuals usually remain awake and aware during the event, though movement and speech are temporarily impaired.

Most commonly, katapleksi is associated with narcolepsy type 1, a condition characterized by daytime sleepiness and pathophysiology related to hypocretin (orexin) deficiency. It can also occur in narcolepsy type 2 or, less commonly, as an isolated phenomenon. The prevailing explanation involves intrusion of REM sleep atonia into wakefulness, linked to abnormalities in the hypocretin/REM sleep regulation system and heightened emotional responsiveness.

Diagnosis relies on clinical history and targeted sleep testing. Polysomnography followed by a multiple sleep latency test helps differentiate cataplexy from seizures or syncope and may reveal rapid eye movement sleep episodes at sleep onset. Measurement of hypocretin-1 in cerebrospinal fluid can support the diagnosis in uncertain cases.

Treatment focuses on controlling symptoms and improving safety and quality of life. Daytime sleepiness is treated with stimulants or wake-promoting agents, while cataplexy is managed with medications such as sodium oxybate or certain antidepressants that reduce REM sleep propensity. Lifestyle adjustments, including planned daytime naps and trigger awareness, complement pharmacotherapy. Treatment is individualized and often requires sleep specialist input.