The main symptoms of narcolepsy are daytime sleepiness and abnormal features of dream sleep (i.e, rapid-eye-movement, or, REM, sleep). A subgroup of patients (~ 1/3rd) have disrupted nocturnal sleep. The usual age of onset is in the mid-to-late teens although it can begin in the pre-teens or at a later age, and it is a life time illness. Daytime sleepiness in genuine narcoleptics typically occurs as irresistible urges to fall asleep – sometimes referred to as “sleep attacks” - at random intervals throughout the waking day. These short bouts of sleep are usually refreshing or ‘restorative’ in quality, as is night-time sleep. Abnormal features of dream sleep include: hallucinations, sleep paralysis, and cataplexy. Patients can experience dream-like auditory or visual hallucinations upon falling asleep or dozing that are termed hypnagogic hallucinations. Sleep paralysis can be a frightening sensation of feeling paralyzed and unable to move upon falling asleep or awakening from sleep that lasts for several minutes. Cataplexy is a symptom unique to narcolepsy in which the patient experiences a sudden loss of muscle tone for tens of seconds to minutes, and these are evoked by emotional situations such as laughter, hearing or telling a joke, fear, or anger. Cataplexy varies greatly in intensity and duration from a patient’s knees buckling or jaw becoming lax briefly, to the eyelids and head drooping (thus, mimicking sleep to an observer), to the patient falling down and being unable to move for several minutes. It is a critical distinction that conscious awareness of the environment is preserved in patients during an attack of cataplexy although it might appear to an observer that the patient has “passed out” or “fainted”. A substantial proportion of patients with genuine narcolepsy have disrupted sleep that can manifest as dream enactment (e.g., rapid-eye-movement (REM) – sleep behavior disorder) and periodic leg movements in sleep.