Narcolepsy is a chronic neurological condition producing disruption to the normal sleep pattern, which produces excessive sleepiness; may occur with or without cataplexy

Cataplexy is a sudden loss of muscle tone and power in response to strong emotion - it always and only occurs as part of narcolepsy

Aetiology

• Equal sex incidence
• Age of onset is typically around adolescence; a smaller number of cases presents at around 35 years

Pathophysiology

• Caused by abnormalities of the brain neurotransmitter hypocretin (orexin), which is a regulator of sleep

Consequences

• Frequently unrecognised, typical delay of 10 years between onset and diagnosis
• Can lead to impairment of social and academic performance

Clinical features

• Daytime sleepiness
  • Involuntary somnolence during eating/talking
  • May be severe, and impossible to resist
• Cataplexy - loss of muscle tone, triggered by emotion
• Hypnagogic hallucinations - hallucinations occurring at sleep onset
• Sleep paralysis - unable to move upon falling asleep or awakening with retained consciousness
• REM sleep behavior disorder (RBD) - 7-36% of patients with RBD have narcolepsy

Investigations

• Overnight polysomnography
• Multiple sleep latency test

Management