Narcolepsia

Narcolepsy is a long-term neurological disorder that affects the brain's ability to control sleep-wake cycles. Individuals with narcolepsy experience excessive daytime sleepiness and uncontrollable episodes of falling asleep during the daytime. These sudden sleep attacks may occur during any type of activity at any time of the day. In a typical sleep cycle, a person enters the rapid eye movement (REM) stage of sleep after about 90 minutes. However, people with narcolepsy often enter REM sleep almost immediately in the sleep cycle, as well as sporadically during the waking hours.

Symptoms

The hallmark symptom of narcolepsy is excessive daytime sleepiness (EDS), where individuals have difficulties staying awake and alert throughout the day. Other symptoms include:

• Cataplexy: A sudden, brief loss of voluntary muscle tone triggered by strong emotions such as laughter.
• Sleep paralysis: The temporary inability to move or speak while falling asleep or upon waking.
• Hypnagogic hallucinations: Vivid, often frightening, dream-like experiences that occur while falling asleep.
• Disturbed nocturnal sleep: Fragmented and often interrupted sleep during the night.

Causes

The exact cause of narcolepsy is unknown, but it is believed to involve multiple factors, including genetic predisposition, autoimmune destruction of hypocretin-producing neurons in the hypothalamus, and environmental triggers. Hypocretin is a neurotransmitter that regulates arousal, wakefulness, and appetite. A significant loss of hypocretin-producing cells has been observed in individuals with narcolepsy, particularly in those who experience cataplexy.

Diagnosis

Diagnosis of narcolepsy is based on the clinical evaluation of symptoms, detailed patient history, and specific sleep studies. Tests include:

• Polysomnography (PSG): An overnight sleep study that records brain waves, blood oxygen levels, heart rate, breathing, and eye and leg movements.
• Multiple Sleep Latency Test (MSLT): A test that measures how quickly a person falls asleep in a quiet environment during the day. It also measures how quickly and how often REM sleep is entered. This is done after a PSG test to ensure the individual has had adequate sleep during the night.

Treatment

There is no cure for narcolepsy, but the symptoms can be managed with medications and lifestyle changes. Treatment may include:

• Stimulants, such as modafinil, to help increase alertness.
• Antidepressants to control cataplexy, sleep paralysis, and hypnagogic hallucinations.
• Sodium oxybate (Xyrem) to improve nighttime sleep and reduce daytime sleepiness and incidents of cataplexy.

Lifestyle adjustments, such as regular sleep schedules, short naps to control daytime sleepiness, and avoiding caffeine and alcohol near bedtime, can also help manage symptoms.

Epidemiology

Narcolepsy is a rare condition, affecting about 1 in 2,000 people. It can occur in both men and women and is typically diagnosed in adolescence or early adulthood, although it can manifest at any age.

See Also

• Sleep disorder
• Hypersomnia
• Sleep apnea
• Insomnia