Narcolepsy

Definition

Narcolepsy is a sleep disorder that disrupts the normal sleep-wake cycle. It is a chronic neurological condition in which a person experiences uncontrollable sleepiness, falling asleep, or napping throughout most days. Although this excessive sleepiness usually occurs on a daily basis, it must occur at least three times a week for at least three months to warrant a diagnosis of narcolepsy.

According to the Narcolepsy Network, this condition affects approximately 1 in 2,000 people in the United States, though many go undiagnosed. Narcolepsy typically first develops in children and young adults and rarely makes a first appearance in older adults. The severity of symptoms may change over time, but narcolepsy is a chronic, lifelong condition once symptoms emerge. 

Symptoms

Narcolepsy has been described in all ethnic groups and in many cultures around the world. The primary feature of narcolepsy is an overwhelming sense of fatigue, causing affected individuals to take multiple daytime naps or simply lapse into sleep at unplanned times throughout the day. Often this sudden lapse into sleep takes the form of a "micro-nap," lasting just seconds. When the sleepiness is severe, a person may continue with their normal activities automatically but will be in a dazed state and not have any memory of their behavior.

Additionally, people with narcolepsy often experience cataplexy, which is a sudden muscle weakness or paralysis. Cataplexy is typically preceded by strong emotions; for instance, person experiencing cataplexy may be seen laughing or joking just before they have a sudden loss of muscle tone and their knees buckle or head drops. Cataplexy is brief, lasting seconds to minutes, and the person remains conscious and aware during the episode, even as their head bobs, jaw drops, or they collapse to the ground.

Approximately 20 to 60 percent of people with narcolepsy experience vivid hypnogogic hallucinations upon falling asleep or just after awakening. People with narcolepsy also commonly have a deficiency of hypocretin, which is a hormone in the brain that regulates wakefulness and appetite. Nocturnal eating and obesity are both common among people with narcolepsy. Temporary sleep paralysis is another symptom of narcolepsy that may occur just as the individual is falling asleep or waking up. 

Causes

Narcolepsy is an abnormality of rapid eye movement (REM) sleep, the most restorative stage of sleep. Although weak muscle tone and vivid, intense dreams are normal features of REM sleep, in people with narcolepsy these events occur during waking moments.

Though the cause is not completely understood, narcolepsy appears to have both an environmental and a genetic component, with a 10- to 40-fold increase in the chance of developing narcolepsy among first-degree relatives. Several factors can trigger narcolepsy, including head trauma, autoimmune disorders, and sudden changes in sleep-wake patterns. 

Treatments

To rule out other conditions that may result in daytime sleepiness, narcolepsy can only be diagnosed through an overnight sleep study. There is no known cure for narcolepsy, but there are several treatment options that can address symptoms and improve life quality, including medication and lifestyle changes. Stimulant and antidepressant medications are among the medicines that have been shown to reduce drowsiness and control cataplexy. Additional treatment strategies include taking short, regularly scheduled naps, maintaining a consistent sleep schedule, avoiding caffeine, alcohol, and smoking, as well as exercising daily. 

References

American Psychiatric Association. (2013). Diagnostic and Statistical Manual of Mental Disorders (5th ed.). Arlington, VA: American Psychiatric Publishing.

National Institute of Neurological Disorders and Stroke

Narcolepsy Network

Last reviewed 03/05/2018