Cataplexy: Sudden Muscle Tone Loss Triggered by Emotions, Linked to Narcolepsy

Cataplexy = brief, bilateral loss of muscle tone with preserved consciousness, triggered by strong emotions (laughter, surprise, anger, excitement).

Pathophysiology

Loss of hypocretin (orexin) neurons in lateral hypothalamus (narcolepsy type 1). Hypocretin normally stabilizes wakefulness and inhibits REM-atonia pathways. Without it, emotion activates amygdala → triggers REM-atonia circuitry → cataplexy.

Clinical Features

• Seconds to minutes; partial (jaw drop, slurred speech, knee buckling) or complete collapse.
• Respiratory and ocular muscles spared.
• Often co-occurs with excessive daytime sleepiness, sleep paralysis, hypnagogic hallucinations.

Treatment

• Sodium oxybate (Xyrem): Gold standard; consolidates sleep, reduces cataplexy.
• Antidepressants: Venlafaxine, fluoxetine, clomipramine (off-label).
• Stimulants: Modafinil, armodafinil, pitolisant for EDS.
• Lifestyle: Scheduled naps, avoid alcohol/caffeine, regular sleep schedule.

Diagnosis: clinical history + polysomnography/MSLT + CSF hypocretin-1 (if available). Cataplexy is pathognomonic for narcolepsy type 1.