Narcolepsy is a well known neurological sleep disorder. It usually starts in adolescence or early adult life and manifests as excessive sleepiness in the wake time.  Patients with narcolepsy may also have ‘cataplexy’ – sudden loss of muscle power when one is emotionally excited, such as when you hear a joke or are taken by surprise. Other features of narcolepsy include vivid dreams, sleep-related hallucinations, sleep paralysis and frequent interruption of sleep at night.  Patients with narcolepsy may also have other sleep disorders such as obstructive sleep apnoea, restless legs syndrome and REM Sleep Behaviour Disorder.