Narcolepsy is a disorder of the nervous system marked by excessive daytime
attacks, and cataplexy (a sudden loss of muscle tone, usually lasting up
to half an hour). The American Psychiatric Association (APA) classifies
narcolepsy as a sleep disorder in the fourth edition of the
Diagnostic and Statistical Manual of Mental Disorders
. The National Institute of Neurological Disorders and Stroke (NINDS)
defines narcolepsy as a "disorder caused by the brain's
inability to regulate sleep-wake cycles normally." The disorder is
sometimes called Gélineau's syndrome because it was first
identified in 1880 by the French neurologist Jean-Baptiste Gélineau.
itself comes from two Greek words that together mean "seized by
Narcolepsy is the second-leading cause of excessive daytime sleepiness
(after obstructive sleep apnea). Persistent sleepiness and sleep attacks
are the hallmarks of this condition. The sleepiness has been compared to
feeling of trying to stay awake after not sleeping for two or three days.
It is not correct, however, to describe people with narcolepsy as sleeping
longer or spending more time asleep in a 24-hour period than people
without the disorder. Although patients with narcolepsy experience
drowsiness and sleep attacks during the daytime, they also wake up
frequently during the nighttime hours. For this reason, narcolepsy is more
accurately described as a disorder of the normal boundaries between sleep
People with narcolepsy fall asleep suddenly—anywhere, at any time,
maybe even in the middle of a conversation. These sleep attacks can last
from a few seconds to more than an hour. Depending on where they occur,
they may be mildly inconvenient or even dangerous. Some people continue to
function outwardly during the sleep episodes, such as talking or putting
things away. But when they wake up, they have no memory of the event.
Narcolepsy is related to the deep, dreaming part of sleep known as rapid
eye movement (REM) sleep. Normally when people fall asleep, they
experience 80 to 100 minutes of non-REM sleep, which is then followed by
about 20 minutes of REM sleep. People with narcolepsy, however, enter REM
sleep immediately. In addition, REM sleep occurs inappropriately
throughout the day in patients with narcolepsy.
There has been considerable debate in the early 2000s over the incidence
of narcolepsy. Some researchers think the disorder is underdiagnosed.
According to NINDS, the disorder affects one American in every 2000, or
about 135,000 people in the general United States population. However, the
rates in other countries vary considerably, from one in 600 people in
Japan to one in 500,000 in Israel. The reasons for these variations in
different ethnic groups are not yet fully understood.
Males and females seem to experience this disorder at about the same rate.
Narcolepsy is a somewhat unusual disorder in terms of age distribution.
Although the disorder has been identified in children as young as three
years of age, most patients with narcolepsy are diagnosed either between
the ages of ten and 25 or between the ages of 40 and 45. It is uncommon
for a person to develop the signs of narcolepsy for the first time after
Causes and symptoms
In 1999 researchers identified the gene that causes narcolepsy on
chromosome 12. The gene allows cells in the hypothalamus (the part of the
brain that regulates sleep behavior) to receive messages from other cells.
When this gene is abnormal, cells cannot communicate properly, and
abnormal sleeping patterns develop. However, not everyone who has the gene
develops narcolepsy; between 12 percent and 35 percent of the United
States population is thought to carry the gene but only 0.02 percent
develop the disorder. Narcolepsy sometimes clusters in families;
first-degree relatives of a person diagnosed with the disorder have a 1
percent to 2 percent risk of developing narcolepsy themselves, or about 10
to 40 times the risk of a person in the general population.
In the late 1990s, three independent research groups discovered a
neuropeptide system in the hypothalamus, the part of the brain that
regulates body temperature and appetite. The newly discovered system,
which has been called the hypocretinergic system, regulates sleep and
wakefulness. The nerve cells, or neurons, in this part of the hypothalamus
secrete substances known as hypocretins or orexins, which regulate the
sleep/wake cycle in humans. There are two of these compounds, known as
orexin-A and orexin-B, or as hypocretin-1 and hypocretin-2. As of the
early 2000s, narcolepsy is thought to be an orexin deficiency syndrome;
that is, it develops when a person's hypothalamus does not secrete
enough orexins to keep the person from falling asleep at inappropriate
times. Samples of cerebrospinal fluid taken from patients with narcolepsy
contain little or no orexins. MRI scans of these patients indicate that
there is some loss of brain tissue in the hypothalamus itself, suggesting
that the neurons responsible for secreting orexins have died.
In a few cases, the first signs of narcolepsy are triggered by traumatic
damage to the part of the brain that governs REM sleep or from a rapidly
growing tumor that puts pressure on this region of the brain. It is also
thought that the hormonal changes of
may affect this region of the brain in some people.
Narcolepsy is defined by four major symptoms:
The symptoms of narcolepsy in children below the age of ten are somewhat
different from the classical signs of the disorder in adolescents and
adults. They may include the following (in addition to cataplexy and
Children between the ages of ten and 12 frequently report falling asleep
in school or being unable to pay attention during class. In some cases a
sudden drop in the child's academic performance is the first
indication of narcolepsy.
Parents who suspect that their child may have narcolepsy should consult a
specialist (usually a pediatric neurologist) and have the child tested in
a sleep clinic. Children with narcolepsy have often been misdiagnosed as
having attention-deficit hyperactivity disorder, while adolescents have
sometimes been misdiagnosed as having substance abuse or
. The sooner narcolepsy is correctly identified, the better the
child's chances of maintaining normal academic and social
Narcolepsy is a complex disorder, and it is not always easy to identify.
It takes ten years on average for an individual to be correctly diagnosed.
The diagnosis of younger patients is additionally complicated by the fact
that children with narcolepsy rarely have all four of the classical
symptoms of the disorder as described in adults. Most often, the first
symptom in children is an overwhelming feeling of fatigue. After several
months or years, cataplexy and the other classical symptoms of the
disorder may appear.
The child's doctor will not be able to diagnose narcolepsy on the
basis of a routine physical examination. If the child has experienced both
excessive daytime sleepiness and cataplexy, a tentative diagnosis may be
made on the basis of the patient's history. In addition, the doctor
may give the child or adolescent a short self-administered list of eight
questions known as the Epworth Sleepiness Scale (ESS). First published by
an Australian doctor in 1991, the ESS asks the person to rate how likely
they are to doze off or fall asleep in eight different situations from
everyday life. A score above ten (maximum score is 24) generally indicates
that the doctor should consider laboratory testing for narcolepsy.
Imaging studies are not helpful in diagnosing narcolepsy, although in some
cases the doctor may order an MRI or CT scan to rule out a brain tumor or
other abnormality in brain structure. Laboratory tests used to evaluate a
person for narcolepsy include an overnight polysomnogram (a test in which
sleep is monitored with electrocardiography, a video camera, and
respiratory parameters). A multiple sleep latency test, which measures
sleep latency (onset) and how quickly REM sleep occurs, may also be used.
People who have narcolepsy usually fall asleep much more rapidly that
people without the disorder, often in less than five minutes.
If the diagnosis is still questionable, a genetic blood test can reveal
the existence of certain substances in people who have a tendency to
develop narcolepsy. Positive test results suggest but do not prove that
the person has narcolepsy. As of the early 2000s, the diagnosis of
narcolepsy also can be confirmed by taking a sample of the
patient's cerebrospinal fluid by a spinal tap and testing it for
the presence of hypocretin-1. Patients with narcolepsy have no
hypocretin-1 in their spinal fluid.
There is no cure for narcolepsy. The disorder is neither progressive nor
fatal, but it is chronic. The symptoms, however, can be managed with a
combination of medications and lifestyle adjustments. Amphetamine-like
are often prescribed to control drowsiness and sleep attacks. Patients
who do not like taking high doses of stimulants may choose to take smaller
doses and make adjustments in their lifestyles, such as napping every
couple of hours, to relieve daytime sleepiness.
are also often effective in treating symptoms of abnormal REM sleep.
Newer nonamphetamine wake-promoting drugs are available to treat
narcolepsy. These medications lack the unpleasant side effects of
amphetamines, particularly jitteriness and
. Modafinil (Provigil) is the most commonly prescribed of the newer
psychostimulants. As of 2004, however, researchers do not know exactly how
modafinil prevents the drowsiness associated with narcolepsy. Its most
common side effect is
. A study published in 2003 reported that modafinil appears to be safe for
use in children.
With discovery of the gene that causes narcolepsy, researchers are hopeful
that therapies can eventually be designed to relieve the symptoms of the
The botanical remedy yohimbe (
) may be useful in promoting alertness. As with any herbal preparation or
medication, however, individuals should check with their healthcare
professional before taking the remedy to treat narcolepsy.
Children with narcolepsy sometimes fall asleep while eating, but the
disorder itself does not cause or lead to
. Adolescents should be advised to avoid tobacco,
, and alcoholic beverages, as these substances can increase daytime
sleepiness in patients with narcolepsy.
The symptoms of narcolepsy are more severe when they develop in children
than when they emerge in adult life. Narcolepsy is not a degenerative
disease, however, and patients do not develop other neurologic symptoms.
In fact, older patients often report that their symptoms decrease in
severity after age 60. Apart from falls or other accidents, narcolepsy
does not affect a person's life expectancy. It can, however,
severely interfere with a young person's ability to study,
, participate in
and other social activities, and develop close relationships with others.
The sooner it is diagnosed and treated, the better the child's
outlook for a happy and productive adult life.
There is no way to prevent narcolepsy as of the early 2000s.
—A symptom of narcolepsy in which there is a sudden episode of
muscle weakness triggered by emotions. The muscle weakness may cause the
person's knees to buckle, or the head to drop. In severe cases,
the patient may become paralyzed for a few seconds to minutes.
—Chemicals secreted in the hypothalamus that regulate the
—A part of the forebrain that controls heartbeat, body
temperature, thirst, hunger, body temperature and pressure, blood sugar
levels, and other functions.
—Another name for hypocretin, a chemical secreted in the
hypothalmus that regulates the sleep/wake cycle. Narcolepsy is sometimes
described as an orexin deficiency syndrome.
—An abnormal episode of sleep in which the patient cannot move
for a few minutes, usually occurring on falling asleep or waking up.
Often found in patients with narcolepsy.
Narcolepsy can be particularly stressful for a family when the affected
, because of
to experiment with
and recreational drugs, and because of resentment about restrictions on
learning to drive or use of the family car. Families with a child
diagnosed with narcolepsy should consider joining a support group for
people affected by the disorder.
American Psychiatric Association.
Diagnostic and Statistical Manual of Mental Disorders,
4th ed., Text Revision. Washington, DC: American Psychiatric Association,
"Sleep Disorders: Narcolepsy." Section 14, Chapter 173 in
The Merck Manual of Diagnosis and Therapy.
Edited by Mark H. Beers, and Robert Berkow. Whitehouse Station, NJ: Merck
Research Laboratories, 2002.
Beuckmann, C. T., and M. Yanagisawa. "Orexins: From Neuropeptides
to Energy Homeostasis and Sleep/Wake Regulation."
Journal of Molecular Medicine
80 (June 2002): 329–42.
Ivanenko, A., R. Tauman, and D. Gozal. "Modafinil in the Treatment
of Excessive Daytime Sleepiness in Children."
4 (November 2003): 579–82.
Kotagal, S. "Sleep Disorders in Childhood."
21 (November 2003): 961–81.
Ohayon, M. M., et al. "Prevalence of Narcolepsy Symptomatology and
Diagnosis in the European General Population."
58 (June 25, 2002): 1826–33.
Silvestri, A. J., et al. "The Central Nucleus of the Amygdala and
the Wake-Promoting Effects of Modafinil."
941 (June 21, 2002): 43–52.
American Sleep Disorders Association.
1610 14th St. NW, Suite 300, Rochester, MN 55901. Web site:
PO Box 42460, Cincinnati, OH 45242. Web site:
National Center on Sleep Disorders Research.
Two Rockledge Centre, 6701 Rockledge Dr., Bethesda, MD 20892. Web site:
National Institute of Neurological Disorders and Stroke (NINDS).
National Institutes of Health. 9000 Rockville Pike, Bethesda, MD 20892.
National Sleep Foundation.
1522 K St., NW, Suite 500, Washington, DC 20005. Web site:
Stanford Center for Narcolepsy.
1201 Welch Rd-Rm P-112, Stanford, CA 94305. Web site:
University of Illinois Center for Narcolepsy Research.
845S. Damen Ave., Chicago, IL 60612. Web site:
Baker, Matthew J., and Selim R. Benbadis. "Narcolepsy."
, October 4, 2004. Available online at
http://www.emedicine.com/neuro/topic522.htm (accessed January 14,
National Institute of Neurological Disorders and Stroke (NINDS).
Narcolepsy Fact Sheet
. Bethesda, MD: NINDS, 2003.