Definition: Narcolepsy is a neurological condition most characterised by excessive daytime sleeping, sudden involuntary episodes of sleep (sleep attacks), cataplexy, sleep-related hallucinations, and sleep paralysis. It is a kind of dyssomnia associated with a disorder of REM (rapid eye movement) sleep. There is strong evidence suggesting that narcolepsy might be an autoimmune disease.

 A person with narcolepsy is likely to become drowsy or to fall asleep, often at inappropriate times and places. Daytime naps may occur with or without warning and may be irresistible. These naps can occur several times a day. They are typically refreshing, but only for up to a couple hours. Drowsiness may persist for prolonged periods of time. In addition, night-time sleep may be fragmented with frequent wakening.

Normally, when an individual is awake, brain waves show a regular rhythm. When a person first falls asleep, the brain waves become slower and less regular. This sleep state is called non-rapid eye movement (NREM) sleep. After about an hour and a half of NREM sleep, the brain waves begin to show a more active pattern again. In narcolepsy, the order and length of NREM and REM sleep periods are disturbed, with REM sleep occurring at sleep onset instead of after a period of NREM sleep. Thus, narcolepsy is a disorder in which REM sleep appears at an abnormal time.
Basically, the brain does not pass through the normal stages of doseing and deep sleep but goes directly into (and out of) rapid eye movement (REM) sleep. This has several consequences:
• Night-time sleep does not include much deep sleep, so the brain tries to "catch up" during the day.
• People with narcolepsy fall quickly into what appears to be very deep sleep.
• They wake up suddenly and can be disoriented when they do.
• They have very vivid dreams, which they often remember.
• People with narcolepsy may dream even when they only fall asleep for a few seconds.

Aetiology / Risk Factors factors that can contribute to the incidence of narcolepsy include
the following:
• Genetics –there appears to be a correlation between narcoleptic individuals and certain variations in HLA genes (these genes code for the protein  hypocretin, which is responsible for controlling appetite and sleep patterns).
• Personal or family history of a utoimmune disorders.
• Stress.

Symptoms & Common signs and symptoms of narcolepsy include:
• Sleepiness: In most cases, the first symptom of narcolepsy to appear is excessive and overwhelming daytime sleepiness.
• Cataplexy: sudden episodes of loss of muscle function, ranging from slight weakness
(such as limpness at the neck or knees, sagging facial muscles, or inability to speak
clearly) to complete body collapse. Episodes may be triggered by sudden emotional
reactions such as laughter, anger, surprise, or fear, and may last from a few seconds to several minutes. The person remains conscious throughout the episode.
• Paralysis: temporary inability to talk or move when waking up. It may last a few seconds to minutes. Often frightening but not dangerous.
• Sleep -related hallucinations: vivid, often frightening, dream-like experiences that occur while doseing or falling asleep (hypnagogic hallucinations) and/or while awakening (hypnopompic hallucinations).
• Automatic behaviour: automatic behaviour occurs when a person continues to function (talking, putting things away, etc.) during sleep episodes, but awakens with no memory of performing such activities.