Narcolepsy (NAR-CO-lep-sy) is a serious, chronic sleep disorder characterized by excessive daytime sleepiness (EDS), fatigue, and sudden sleep attacks, due to the inability of the brain to regulate sleep-wake cycles normally.
The term “narcolepsy” was introduced by the French physician Jean-Baptiste-Édouard Gélineau (1859–1928) in 1876 and literally means a sleep attack (narco means “stupor” and lepsis means “attack”), and the condition is the result of a defect in the ability of the brain to regulate sleepwake cycles.
Narcolepsy affects nearly 1 in 3,000 men and women in the United States. It affects men and women equally and appears throughout the world. Symptoms usually start in childhood and adolescence but are often not recognized until between age 35 and 45. Narcoleptic symptoms are often attributed to other conditions such as depression * , epilepsy * , or even laziness.
Normally, there are four to six sleep cycles during eight hours of sleep. While falling asleep, brain waves slow down and enter into non–rapid eye movement (NREM) sleep. The purpose of NREM is restorative and refreshing sleep, and it lasts for up to 90 to 120 minutes. This period is followed by rapid eye movement (REM) sleep. REM sleep is characterized by complete paralysis * of all muscles except those of the eye, which leads to rapid eye movements, hence the name. Dreaming occurs most often during this stage, but due to muscle paralysis, dreams cannot be acted out. In narcolepsy, the NREM phase is abbreviated or absent with a quick onset of REM phase, which results in nighttime and daytime sleep attacks with accompanying muscle paralysis and vivid dreaming.
There are four classic features of narcolepsy, and only about one-third of patients have all symptoms.
The word “cataplexy” is Greek (kata means “down” and plexy means seizure * ). It refers to a sudden loss of voluntary muscle control, often triggered by a strong feeling such as what one feels while laughing or when angry. About 70 percent of narcoleptics have experienced at least one episode of cataplexy. The severity of cataplexy can range from mild (slurred speech) to severe (knees buckling and falling down). The episode lasts a few seconds to a few minutes, and the person is always conscious. The number of attacks varies from one per day to a few per year.
Sleep paralysis is characterized by brief (one- to two-minute) episodes of inability to talk or move while awakening from sleep or while falling asleep. These episodes are quite frightening, as the person can remember the episode but has no control over it and cannot prevent it. They are often associated with hypnagogic hallucinations. These attacks, however, do not cause any permanent damage, and people recover quickly.
Hallucinations are vivid and often frightening dreamlike experiences that occur while falling into REM sleep (hypnagogic) or on awakening (hypnapompic). They occur due to the intrusion of REMassociated dreaming into a wakeful state, resulting in fragmented and restless nighttime sleep with patients acting out their dreams sometimes.
Narcolepsy occurs sporadically and has some genetic predisposition * . About 50 to 90 percent of patients with narcolepsy and cataplexy have an antigen * on the surface of white blood cells, which is a marker for the disease, but is not the cause of it. For example, 20 percent of normal individuals also have this particular antigen. This specific antigen type is thought to predispose an individual to develop narcolepsy through a hitherto unknown immune system * disturbance. Some 8 to 12 percent of narcoleptics have a close family member with narcolepsy. Relatives of a narcoleptic have a 1 to 2 percent chance of having narcolepsy and a 4 percent chance of having excessive daytime sleepiness (EDS).
The exact cause of narcolepsy was unknown as of 2016. It is thought that some sort of trigger (such as an infection) might activate the immune system of the individual to attack and destroy specific cells in a part of the brain called the hypothalamus * that normally secrete a chemical called hypocretin, leading to its reduction or complete absence. Hypocretin helps to stabilize wakefulness by stimulating certain alertness centers in the brain and prevents inappropriate transition to REM sleep. It also inhibits REM sleep and REM-associated behavior, such as sleep paralysis and dreaming. The total lack or decrease of hypocretin results in the symptoms of narcolepsy. Rarely, patients may have a defect in a receptor, leading to normal but ineffective levels of hypocretin. Narcolepsy can also be a manifestation of rare genetic * disorders such as Prader-Willi or Niemann-Pick.
Polysomnogram consists of monitoring brain waves (electroencephalogram * [EEG]), muscle activity, breathing, and heart rhythm (electrocardiogram) by electrodes and monitors attached to the scalp, face, eyes, jaw, limbs, chest, and abdomen. The patient sleeps overnight in a monitored environment, such as a sleep clinic. Based on the pattern of NREM, REM, and REM-associated behaviors, the diagnosis of narcolepsy is made, and other diagnoses such as sleep apnea are excluded. Narcoleptics fall asleep quickly, go into REM sleep rapidly, exhibit REM behaviors such as cataplexy, and have frequent nighttime awakenings.
The multiple sleep latency test consists of four or five scheduled naps during the day, with naps spaced two hours apart. Based on the time it takes an individual to fall asleep, narcolepsy can be diagnosed. A normal person takes 15 to 20 minutes to fall asleep and gradually progresses through NREM to REM sleep, whereas a narcoleptic falls asleep within five minutes and enters rapidly into REM sleep.
Levels of hypocretin can be measured in the cerebrospinal fluid * . A narcoleptic has low or absent hypocretin levels. Testing for the particular antigen can be done, but as discussed earlier, it is not specific and does not prove that a person has narcolepsy. These research tests are available only at specialized centers.
Narcolepsy is a chronic disorder like diabetes and cannot be cured. Treatment needs to be tailored to the most disturbing symptoms. It may take several months to get to an appropriate regimen, and even then, treatment may result in only partial symptom relief.
Narcolepsy is often treated with medications, namely stimulants and antidepressant medications * .
Modafinil is a non-amphetamine medication approved by the U.S. Food and Drug Administration (FDA) in 1999. It does not have addiction potential, but headache is the most common side effect.
Tricyclic antidepressants (Imipramine) and serotonin reuptake inhibitors (SSRIs) such as fluoxetine (Prozac) suppress REM sleep and REM sleep behavior. Side effects include impotence * , heart rhythm abnormalities, and high blood pressure.
Sodium oxybate (gamma-hydroxybutyrate, Zyrem) is the only medication that controls cataplexy and EDS in patients with resistant narcolepsy. It was approved by FDA in 2002. It is an illegal drug in several countries and is popularly called the “date rape” drug. Side effects include breathing disturbances and bed-wetting. Due to safety concerns and abuse potential, it is subject to FDA regulation.
Caution is to be exercised while taking any of the above medications because they can adversely interact with over-the-counter cough and cold remedies. As of 2009, experiments involving stem cell * transplantation and direct delivery of hypocretin into the brain were being conducted in animals, but this research was considered a long way away from human studies.
Behavioral strategies include the following:
Narcoleptics should avoid engaging in activities that need long periods of alertness such as operating hazardous machinery or taking long drives. Narcoleptics can request reasonable workplace accommodations in accordance with the Americans with Disabilities Act. Children should work with their school personnel to facilitate modification of class schedules and to take medications. Finally, people around the patient should know about the condition, so they can be supportive and help with the emotional and physical aspects of the condition.
See also Sleep Disorders: Overview
Troxel, Wendy M., Brett Ewing, and Elizabeth J. D'Amico. “Examining Racial/Ethnic Disparities in the Association Between Adolescent Sleep and Alcohol or Marijuana Use.” Journal of the National Sleep Foundation 1 (2015): 104–108. http://www.sleephealthjournal.org/article/S2352-7218(15)00060-1/pdf (accessed October 23, 2015).
Sleep Education. “Narcolepsy.” American Academy of Sleep Medicine. http://www.sleepeducation.com/essentials-in-sleep/narcolepsy/overview-facts (accessed October 23, 2015).
Narcolepsy Network. 46 Union Dr., #A212, North Kingstown, RI 02852. Toll-free: 888-292-6522. Website: http://narcolepsynetwork.org (accessed October 23, 2015).
National Sleep Foundation. 1010 North Globe Rd., Suite 310, Arlington, VA 22201. Telephone: 703-243-1697. Website: http://sleepfoundation.org (accessed October 23, 2015).
* depression (de-PRESH-un) is a mental state characterized by feelings of sadness, despair, and discouragement.
* epilepsy (EP-i-lep-see) is a condition of the nervous system characterized by recurrent seizures that temporarily affect a person's awareness, movements, or sensations. Seizures occur when powerful, rapid bursts of electrical energy interrupt the normal electrical patterns of the brain.
* paralysis (pah-RAH-luh-sis) is the loss or impairment of the ability to move some part of the body.
* seizures (SEE-zhurs) are sudden bursts of disorganized electrical activity that interrupt the normal functioning of the brain, often leading to uncontrolled movements in the body and sometimes a temporary change in consciousness.
* genetic predisposition is a tendency to get a certain disease that is inherited from a person's parents.
* antigen (AN-tih-jen) is a substance that is recognized as a threat by the body's immune system, which triggers the formation of specific antibodies against the substance.
* immune system (im-YOON SIStem) is the system of the body composed of specialized cells and the substances they produce that helps protect the body against disease-causing germs.
* hypothalamus (hy-po-THAL-uhmus) is a brain structure located deep within the brain that regulates automatic body functions such as heart rate, blood pressure, temperature, respiration, and the release of hormones.
* genetic (juh-NEH-tik) refers to heredity and the ways in which genes control the development and maintenance of organisms.
* electroencephalogram is an instrument that records the electrical activity of the brain.
* cerebrospinal fluid (seh-ree-broSPY-nuhl) is the fluid that surrounds the brain and spinal cord.
* antidepressant medications are used for the treatment and prevention of depression.
* amphetamines (am-FET-ameenz) are stimulants, drugs that produce a temporary feeling of alertness, energy, and euphoria.
* palpitation is the sensation of a rapid or irregular heartbeat.
* addiction (a-DIK-shun) is a strong physical or psychological dependence on a physical substance.
* impotence (IM-po-tens) is failure of a man to achieve or to maintain an erection.
* stem cell an unspecialized cell that gives rise to differentiated cells.