Diagnosis:

This is a clinical diagnosis supported by findings on polysomnogram

Clinical features:

Daytime hypersomnolance, wake up refreshed
Cataplexy (sudden loss of muscle tone triggered by emotional situations)
Hypnogogic & hypnopopic hallucinations
Sleep paralysis (patient wakes from sleep but tone is still absent, last 10min)

Findings on investigations:

MSLT (multiple sleep latency test): decreased latency for REM sleep i.e. <8min +2 sleep-onset REM periods
CSF hypocretin-1 (formerly orexin A): low in patients with cataplexy, <110 pg/ml

Treatment:

Amfetamines: Dextroamfetamine P.O.
Antidepressants for cataplexy