Narcolepsy is a neurological disorder caused by the brain’s inability to regulate sleep-wake cycles normally. The disease is often associated with excessive daytime sleepiness, sudden sleep attacks, dream-like hallucinations, and a condition called sleep paralysis. Its prevalence in the developed world is approximately the same as that of multiple sclerosis or Parkinson’s disease. However, with increased public education about narcolepsy and physician training in the diagnosis and treatment of sleep disorders, these figures are expected to rise.
In order to understand the basics of narcolepsy, it is important to first review the features of “normal sleep.” Sleep happens in cycles. When we fall asleep, we initially enter a light stage of sleep and then progress into increasingly deeper stages. Both light and deep sleep stages are called non-REM (rapid eye movement) sleep. After about 90 minutes, we enter the first stage of REM sleep, which is the dreaming portion of sleep, and throughout the night we alternate between stages of REM and non-REM sleep. For people with narcolepsy, sleep begins almost immediately with REM sleep and fragments of REM may occur involuntarily throughout the waking hours. When you consider that, during REM sleep our muscles are paralyzed and dreaming occurs, it is not surprising that narcolepsy is associated with paralysis, hallucinations, and other dream-like and debilitating symptoms.
- Excessive daytime sleepiness – this is usually the first symptom to appear in people who have narcolepsy.
- Cataplexy – cataplexy is a sudden loss of muscle tone, usually triggered by emotional stimuli such as laughter, surprise, or anger. It may involve all muscles and result in collapse.
- Hypnagogic hallucinations – during transition from wakefulness to sleep, the patient has bizarre, often frightening dream-like experiences that incorporate his or her real environment.
- Sleep paralysis – a temporary inability to move during sleep-wake transitions. Sleep paralysis may last for a few seconds to several minutes and may accompany hypnapompic hallucinations.
- Fragmented nocturnal sleep – coupled with nightmares, and restlessness.