What is Narcolepsy?
Narcolepsy is a sleep disorder that is characterized by excessive sleepiness, sleep attacks, sleep paralysis, hallucinations and, for some, sudden loss of muscle control (cataplexy). It affects roughly 1 in 2,000 to 3,000 people but can go undiagnosed for many years. Narcolepsy with cataplexy has a known cause, related to a loss of cells in the brain that secrete hypocretin (also called orexin).Hypocretin is a chemical in the brain that is important for regulating wakefulness.
With narcolepsy, the boundaries between sleep and wakefulness are blurred, causing a person to feel very sleepy and fatigued during the day, have vivid dream-like hallucinations and paralysis while falling asleep or waking up, and experience disrupted nighttime sleep.Narcolepsy is often accompanied by cataplexy, a sudden loss of muscle control that can cause a person to collapse, slump over, or slur words without much warning. The disorder usually has its onset in childhood or adolescence. While there’s currently no cure for narcolepsy, there are treatments and lifestyle changes that greatly improve the symptoms.
Narcolepsy is a sleep disorder characterized by excessive sleepiness, sleep paralysis, hallucinations, and in some cases episodes of cataplexy (partial or total loss of muscle control, often triggered by a strong emotion such as laughter). Narcolepsy occurs equally in men and women and is thought to affect roughly 1 in 2,000 people. The symptoms appear in childhood or adolescence, but many people have symptoms of narcolepsy for years before getting a proper diagnosis.
People with narcolepsy feel very sleepy during the day and may involuntarily fall asleep during normal activities. In narcolepsy, the normal boundary between awake and asleep is blurred, so characteristics of sleeping can occur while a person is awake. For example, cataplexy is the muscle paralysis of REM sleep occurring during waking hours. It causes sudden loss of muscle tone that leads to a slack jaw, or weakness of the arms, legs, or trunk. People with narcolepsy can also experience dream-like hallucinations and paralysis as they are falling asleep or waking up, as well as disrupted nighttime sleep and vivid nightmares.
Narcolepsy with cataplexy is caused by the loss of a chemical in the brain called hypocretin. Hypocretin acts on the alerting systems in the brain, keeping us awake and regulating sleep wake cycles. In narcolepsy, the cluster of cells that produce hypocretin—located in a region called the hypothalamus—is damaged or completely destroyed. Without hypocretin, the person has trouble staying awake, and also experiences disruptions in the normal sleep-wake cycles.
Currently there is no cure for narcolepsy, but medications and behavioral treatments can improve symptoms for people so they can lead normal, productive lives.
In a typical sleep cycle, we initially enter the early stages of sleep followed by deeper sleep stages and ultimately (after about 90 minutes) rapid eye movement (REM) sleep. For people suffering from narcolepsy, REM sleep occurs almost immediately in the sleep cycle, as well as periodically during the waking hours. It is in REM sleep that we can experience dreams and muscle paralysis -- which explains some of the symptoms of narcolepsy.
What Causes Narcolepsy?
The cause of narcolepsy is not known; however, scientists have made progress toward identifying genes strongly associated with the disorder. These genes control the production of chemicals in the brain that may signal sleep and awake cycles. Some experts think narcolepsy may be due to a deficiency in the production of a chemical called hypocretin by the brain. In addition, researchers have discovered abnormalities in various parts of the brain involved in regulating REM sleep. These abnormalities apparently contribute to symptom development. According to experts, it is likely narcolepsy involves multiple factors that interact to cause neurological dysfunction and REM sleep disturbances.
What Are the Symptoms of Narcolepsy?
Symptoms of narcolepsy include:
- Excessive daytime sleepiness (EDS): In general, EDS interferes with normal activities on a daily basis, whether or not a person with narcolepsy has sufficient sleep at night. People with EDS report mental cloudiness, a lack of energy and concentration, memory lapses, a depressed mood, and/or extreme exhaustion.
- Cataplexy: This symptom consists of a sudden loss of muscle tone that leads to feelings of weakness and a loss of voluntary muscle control. It can cause symptoms ranging from slurred speech to total body collapse, depending on the muscles involved, and is often triggered by intense emotions such as surprise, laughter, or anger.
- Hallucinations : Usually, these delusional experiences are vivid and frequently frightening. The content is primarily visual, but any of the other senses can be involved. These are called hypnagogic hallucinations when accompanying sleep onset and hypnopompic hallucinations when they occur during awakening.
- Sleep paralysis : This symptom involves the temporary inability to move or speak while falling asleep or waking up. These episodes are generally brief, lasting a few seconds to several minutes. After episodes end, people rapidly recover their full capacity to move and speak.