Narcolepsy

Narcolepsy, or Gelineau syndrome, is a rare sleep disorder characterized by excessive daytime sleepiness, uncontrollable sleep attacks, and occasionally cataplexy (sudden loss of muscle tone). It is a chronic hypersomnia that has no cure.

There are two types of narcolepsy based on how it manifests:

• Type 1 narcolepsy: with cataplexy and decreased levels of hypocretin, a neurotransmitter involved in regulating the sleep-wake cycles and managing strong emotions.
• Type 2 narcolepsy: without cataplexy and with normal levels of hypocretin.

In narcolepsy, the normal boundaries between sleep and wakefulness are not maintained, in addition to having a dysregulation of the REM phase. Narcoleptics enter the REM phase almost immediately upon falling asleep, and cataplexy and other symptoms are intrusions of REM sleep during wakefulness.

Symptoms

The typical symptoms of narcolepsy include:

• Constant or excessive daytime sleepiness.
• Sleep attacks: They begin with intense sleepiness and double or blurred vision. They usually last between 20 and 60 minutes and relieve the sleepiness, but only for a few hours. The frequency of the attacks is highly variable; they may happen several times a day or be spaced out over a longer period.
• Cataplexy: Sudden bilateral muscle loss usually triggered by intense emotions, generally anger, laughter, or excitement. Cataplexy may or may not accompany the sleep attacks. It can last for several minutes and cause total muscle weakness, even collapse, or difficulty speaking.
• Disturbances in nighttime sleep: Very brief REM sleep latency and fragmented sleep with multiple awakenings.
• Sleep paralysis: A phenomenon where the person is unable to move, speak, or even breathe normally when starting or ending sleep (when entering or leaving the REM phase), despite being fully awake and conscious. It is usually accompanied by visual, auditory, or sensory hallucinations. The episode ends spontaneously after a few minutes.
• Hypnagogic hallucinations: Very vivid and diverse daydreams experienced at the beginning of sleep. They often feature very intense and disproportionate visual components and may include auditory, olfactory, and tactile sensations. Although less frequent, they can also occur at the end of sleep (hypnopompic hallucinations).

The first symptom that appears is hypersomnolence; the others may appear even years later and persist throughout life. Daytime sleepiness, sleep attacks, and cataplexy are considered basic symptoms, as sleep paralysis and hallucinations may occur in people who do not have narcolepsy, and not all narcoleptics experience them.

Causes

The exact cause of narcolepsy is unknown, although several predisposing factors are considered. On one hand, it is believed that there is a genetic component related to the presence of certain human leukocyte antigens (HLA), proteins that help the immune system differentiate between its own cells and foreign substances. The antigens associated with narcolepsy are HLA DR2 and HLA DQB1*0602, although it is not known why these antigens predispose to narcolepsy. On the other hand, the concentration of hypocretin is reduced in type 1 narcolepsy patients due to the loss of hypothalamic hypocretin-producing neurons. This loss is believed to be of immune origin.

Risk Factors

Since there is no specific cause, only the following risk factors have been described:

• Age: It typically begins between 10 and 30 years old.
• Family history.

Complications

Narcolepsy has serious consequences in the daily lives of patients. Both sleep attacks and cataplexy episodes, sudden and unavoidable, can be dangerous due to:

• Risk of falls, blows, or accidents, especially if they occur while driving, cooking, or handling tools.
• Impaired concentration, memory, and reflexes that can negatively affect the patient's work or academic responsibilities.
• Misunderstanding and reproach from others for the ability to fall asleep anywhere, which can severely affect their social life.
• Increased tendency to gain weight, due to lower basal metabolism and changes in eating habits.

Prevention

There is no way to prevent narcolepsy; only its symptoms can be treated and cataplexy can be reduced by avoiding triggering factors.

What doctor treats narcolepsy?

Narcolepsy is diagnosed and treated in the sleep unit by specialists from various disciplines, such as neurology, neurophysiology, and psychiatry.