Narcolepsy is considered a primary hypersomnia (excessive sleepiness) condition. Primary means the condition is not caused by another disease. The word narcolepsy comes from two Greek words roughly translated as "seized by numbness." The two primary symptoms in narcolepsy reflect this phrase:
Some patients experience other symptoms:
Rapid eye movement (REM) sleep is abnormal in narcolepsy. (REM sleep is the active, dreaming phase of sleep.) In fact, narcolepsy is sometimes defined as the loss of boundaries between wakefulness, non-REM sleep, and REM sleep.
Excessive Sleepiness. All people with narcolepsy experience excessive sleepiness during the day with episodes of falling asleep rapidly and inappropriately, even when fully involved in an activity. It is sometime described as an irresistible daytime need for naps, which will generally refresh the patient. These events may be characterized by the following behaviors:
Cataplexy. Cataplexy is an abrupt but temporary loss of muscle tone or strength that results in an inability to move and always occurs during wakefulness. Symptoms of excessive daytime sleepiness may be present for years before symptoms of cataplexy develop. About two thirds of patients with narcolepsy have symptoms of cataplexy. The following events may be triggers for cataplexy:
Muscle reflexes are completely absent during a cataplectic attack. Cataplectic attacks can be very minimal and appear as passing weakness or affecting only the eyelids and face. They may, on the other hand, be so severe that they weaken the whole body. In the most severe form of cataplexy, attacks can recur repeatedly for hours or days. Abrupt withdrawal from certain drugs used to treat narcolepsy, notably clomipramine, can trigger these severe symptoms.
Cataplexy may have the following characteristics:
Atonia. Atonia is a sense of paralysis that occurs between wakefulness and sleep, usually upon waking or sometimes at the onset of sleep. The person is conscious but cannot speak, move (cannot even open their eyes), or breathe deeply. Atonia rarely lasts beyond 20 minutes, but when it first occurs the experience can be terrifying, particularly if the patient also develops hallucinations.
Hypnagogic Hallucinations. Hypnagogic hallucinations are dreams that intrude on wakefulness, which can cause visual, auditory, or touchable sensations. They occur between waking and sleeping, usually at the onset of sleep, and can also occur about 30 seconds after a cataplectic attack.
Such symptoms may also appear in other sleep disorders and are probably related to extreme sleepiness. In general, cataplexy must also be present for a clear diagnosis of narcolepsy. It is possible, however, for some patients with narcolepsy to experience hypnagogic or hypnopompic hallucinations and daytime sleepiness and not cataplexy.
Microsleep and Automatic Behavior. In some cases, patients have so-called microsleep episodes, in which they behave automatically without conscious awareness. Such automatic behavior may not be recognized as part of a disorder by either patients or the people around them. Some examples include:
Disturbed Sleep. Nighttime sleep is often disturbed in narcolepsy, bthe disturbance is usually mild to moderate and does not account for the daytime sleepiness experienced by people with narcolepsy.
Periodic Limb Movement Disorder. Many patients with narcolepsy experience periodic limb movement disorder (PLMD; formerly known as nocturnal myoclonus). In PLMD, the leg muscles involuntarily contract every 20 - 40 seconds during sleep, occasionally arousing the patient. The patient is usually unaware of the limb movements, but bed partners may notice the movements..
Most people need about 8 hours of sleep each day. Individual adults differ in the amount of sleep they need to feel well rested, however. (Infants may sleep as many as 16 hours a day.)
The daily cycle of life, which includes sleeping and waking, is called a circadian (meaning "about a day") rhythm, commonly referred to as the biological clock. Hundreds of bodily functions follow biologic clocks, but sleeping and waking comprise the most prominent circadian rhythm. The sleeping and waking cycle is about 24 hours. (If confined to windowless apartments, with no clocks or other time cues, sleeping and waking as their bodies dictate, humans typically live on slightly longer than 24-hour cycles.) The daily sleep/wake cycle usuallyfollows the following pattern:
Daily rhythms intermesh with other factors that may interfere or change individual patterns:
Sleep consists of two distinct states that alternate in cycles and reflect differing levels of brain nerve cell activity.
Non-Rapid Eye Movement Sleep (Non-REM). Non-REM sleep is also termed quiet sleep. Non-REM is further subdivided into three stages of progression:
With each descending stage, awakening becomes more difficult. It is not known what governs Non-REM sleep in the brain. A balance between certain hormones, particularly growth and stress hormones, may be important for deep sleep.
Rapid Eye-Movement Sleep (REM). REM sleep is termed active sleep. Most vivid dreams occur in REM sleep. REM-sleep brain activity is comparable to that in waking, but the muscles are totally relaxed, possibly preventing people from acting out their dreams. In fact, except for vital organs like lungs and heart, the only muscles not relaxed during REM are the eye muscles. REM sleep may be critical for learning and for day-to-day mood regulation. When people are sleep-deprived, their brains must work harder than when they are well rested.
The REM/Non-REM Cycle. The cycle between quiet (non-REM) and active (REM) sleep generally follows this pattern:
Narcolepsy has a genetic component and tends to run in families. An estimated 8 - 10% of people with narcolepsy have a close relative who has the disorder. An individual with a family member who has narcolepsy is 20 - 40 times more likely to have narcolepsy, compared to a person with no family history of the disease.
However, genetics are not the only factor involved in narcolepsy. Narcolepsy most likely involves a combination of genetics and one or more environmental triggers, such as infection, trauma, hormonal changes, immune system problems, or stress. Researchers are looking for specific genetic mutations that may make individuals susceptible to this disorder, and have discovered recently that most affected individuals carry the HLA DQB1(*)0602 gene. More recent studies also show that the TCR-alpha gene, which interacts with the HLA genes, is also involved in narcolepsy.
It has been theorized that narcolepsy may be an autoimmune disease, in which the immune system may be tricked into perceiving its own proteins to be antigens. (Antigens are foreign substances targeted for attack by immune factors in the body.)
Important autoimmune diseases include multiple sclerosis, rheumatoid arthritis, systemic lupus erythematosus, and type 1 diabetes. In such diseases, the immune system overproduces potent factors called cytokines, which cause inflammation and injury in the susceptible cells and tissues affected by the disease. Most autoimmune diseases also tend to afflict those with particular genetically determined molecules of the immune system called human leukocyte antigens (HLAs).
Some research suggests that an immune attack in narcolepsy may occur against cells containing the brain peptide hypocretin (orexin). Hypocretin deficiency is the major component of narcolepsy with cataplexy. Recent studies have shown a reduced amount of hypocretin-positive neurons in patients with narcolepsy with cataplexy. Hypocretin deficiencies might set off chemical responses that produce sleep attacks.
HLAs, particularly the above-mentioned subgroup known as (HLA)DQB1-0602, have been strongly associated with narcolepsy and low levels of hypocretin. Narcolepsy patients who carry this HLA group tend to have a specific collection of symptoms that include cataplexy and periodic limb movement disorder. However, roughly 20% of people without narcolepsy also carry these HLA types.
Narcolepsy affects about 1 in 2,000 people. Experts estimate that around 135,000 - 200,000 Americans have narcolepsy, but the number may be higher. Only about 25% of people who have narcolepsy are actually diagnosed with the disorder. Patients are often mistakenly diagnosed with other conditions, such as psychiatric or emotional problems. Many patients wait decades before receiving a proper diagnosis.
Narcolepsy symptoms usually first appear in adolescence or young adulthood. However, narcolepsy can begin at any age. Growing evidence suggests that the disorder may emerge in early childhood in many patients. It can often be misdiagnosed as another disorder, such as ADHD or depression. People who develop it at a young age often have a family history of the disease and a severe condition, suggesting that genetic factors are important in this group.
Narcolepsy is a life-long problem, but it is not progressive. Symptoms may even lessen over time, but they never completely disappear. In older adults, cataplexy may lessen over time, but sleep disturbances at night may worsen.
Perhaps the most serious consequence of narcolepsy is the high risk for accidents. In one survey, almost 75% of patients with narcolepsy reported falling asleep while driving, and 56% reported nearly having accidents. Other common narcolepsy-related accidents include burns from touching hot objects, cuts from sharp objects, and breaking things.
Some studies report that people with narcolepsy have problems with memory, thinking, and attention. Whether these problems are more likely to be due to tiredness and episodes of sleepiness than to brain abnormalities is not clear.
People with narcolepsy suffer emotional and social difficulties caused by their uncontrollable sleep episodes and cataplexy. Studies have reported rates of depression in people with narcolepsy ranging from 30 - 57%. (In the general population, the prevalence of depression is 8%.) Studies have shown severe emotional and social dysfunction in all areas, including work, relationships, and leisure activities. Men with narcolepsy frequently suffer from sexual problems. Some experts believe that the psychological and social effects are more serious than those caused by epilepsy (for which narcolepsy can be mistaken).
Obesity. People with narcolepsy are at high risk for obesity compared to the general population. This could be a consequence of low activity level, but research also indicates that deficiencies in the brain peptide hypocretin may play a role in both narcolepsy and eating behaviors, which could increase the risk for obesity.
Although narcolepsy is a physical disorder, doctors are still very likely to misdiagnose patients as having psychological problems. In most cases, narcolepsy is not diagnosed for up to 10 - 15 years after the symptoms began. To determine specific sleep disorders, the doctor will take a medical and family history. The patient should tell the doctor about any medications the patient takes. The symptoms of narcolepsy are relatively easy to recognize if a patient reports all of the major symptoms:
Diagnosis based only on symptoms, however, is often problematic for various reasons:
In the future, measurements of hypocretin-1 in the cerebrospinal fluid may prove valuable in identifying difficult to diagnose cases of narcolepsy, since hypocretin is often absent in patients with the condition.
A doctor may administer certain questionnaires on sleeping habits, such as the Stanford Sleepiness Scale or the Epworth Sleepiness Scale.
The Epworth Sleepiness Scale. The Epworth Sleepiness Scale (ESS) uses a simple questionnaire to measure excessive sleepiness and differentiate it from normal daytime sleepiness.
The Epworth Sleepiness Scale
Chance of Dozing
0 = no chance of dozing
1 = slight chance of dozing
2 = moderate chance of dozing
3 = high chance of dozing
Sitting and reading
(Indicate a score of 0 - 3)
(Indicate a score of 0 - 3)
Sitting inactive in a public place (a theater or a meeting)
(Indicate a score of 0 - 3)
As a passenger in a car for an hour without a break
(Indicate a score of 0 - 3)
Lying down to rest in the afternoon when circumstances permit
(Indicate a score of 0 - 3)
Sitting and talking to someone
(Indicate a score of 0 - 3)
Sitting quietly after a lunch without alcohol
(Indicate a score of 0 - 3)
In a car, while stopped for a few minutes in traffic
(Indicate a score of 0 - 3)
1 - 6: Getting enough sleep
4 - 8: Tends to be sleepy but is average
9 - 15: Very sleepy and should seek medical advice
Over 16: Dangerously sleepy
The multiple sleep latency test (MSLT) uses a machine that measures the time it takes to fall asleep lying in a quiet room during the day. The patient takes 4 or 5 scheduled naps 2 hours apart. People with healthy sleep habits fall asleep in about 10 - 20 minutes. In patients with narcolepsy, polysomnography (see below) plus MSLT will show a much shorter duration of time (fewer than 8 minutes) from wakefulness into sleep. At least 2 of the naps are REM-onset (the active sleep phase associated dreaming). The test has limitations, however. There is no clear definition of exactly which abnormal results would indicate narcolepsy. It is most useful for measuring the severity of the problem. The Epworth Sleepiness Scale may be more accurate in differentiating narcolepsy from normal daytime sleepiness.
An overnight sleep study, called polysomnography, can be a valuable means for determining the basic cause of sleepiness. The patient arrives at the sleep center about 2 hours before bedtime without having made any changes in daily habits. The patient will be monitored by a variety of devices while sleeping:
These instruments record activity as the patient passes, or fails to pass, through the various sleep stages.
Ruling out Other Sleep Disorders. Other sleep disorders can share some or all of the symptoms of narcolepsy:
Ruling out Psychological Disorders. In one study, 40% of patients who actually had narcolepsy had been diagnosed incorrectly with some psychological or psychiatric problem. Certainly, patients with narcolepsy have emotional difficulties because of the condition, and it is often difficult, particularly for a nonspecialist, to detect the physical problem. Even worse, hypnagogic hallucinations may result in diagnoses of schizophrenia or bipolar disorder, which are treated with potent antipsychotic drugs that have severe side effects and are useless for narcolepsy.
Ruling out Epilepsy. Narcolepsy can easily be mistaken for epilepsy, a group of disorders that cause seizures. Case studies have reported a misdiagnosis of epilepsy in patients who were actually experiencing cataplexy and sleep paralysis.
Other Causes of Persistent Fatigue. A number of conditions can cause persistent fatigue and should be ruled out, including chronic fatigue syndrome.
These conditions may also worsen sleep paralysis in narcolepsy. Narcolepsy sleep paralysis usually occurs at the onset of sleep and is chronic.
Lifestyle treatment of narcolepsy includes taking three or more scheduled naps throughout the day. Patients should also avoid heavy meals and alcohol, which can interfere with sleep.
People with mild narcolepsy symptoms who do not need medication may be able to maintain alertness with sleep scheduling. The role of scheduled naps for patients who are responding to medications for narcolepsy remains unclear.
Medications for narcolepsy target the major symptoms of sleepiness and cataplexy. Stimulant drugs are used to manage excessive daytime sleepiness while antidepressants and other compounds address cataplectic symptoms. The Food and Drug Administration (FDA) has approved three drugs specifically for the treatment of narcolepsy. They are now the first-line treatments:
Modafinil. Modafinil (Provigil) is a drug used to treat the excessive sleepiness associated with narcolepsy and other sleep disorders. It has largely replaced methylphenidate (Ritalin) and other stimulants for treatment of narcolepsy sleepiness. Patients who switch to modafinil from stimulants such as methylphenidate have few problems if they gradually taper off the stimulant dose.
Modafinil helps patients with narcolepsy stay awake during the day. While only some experience normal wake times, patients taking modafinil often have up to a 50% improvement in the ability to stay awake, as well as a 25% reduction in the number of involuntary sleep episodes. It has not been proven to be safe in pregnant women. Pregnant women or those wishing to get pregnant should discuss the risks and benefits of this medication with their doctors.
Some of modafinil's additional benefits include what it does not do:
Side effects of modafinil may include:
Armodafinil (Nuvigil) is a newer drug, which is nearly identical to modafinil. In clinical trials comparing it with placebo, armodafinil improved wakefulness, memory, attention, and fatigue in patients with narcolepsy.
In October 2007, the FDA added new safety information to the prescribing label of modafinil (Provigil) and armodafinil (Nuvigil). The new information warns that:
Stimulants. Medications that act as stimulants are standard treatments for narcolepsy. They include:
Methylphenidate and dextroamphetamine last for 2 - 5 hours and used to be the standard drugs for excessive daytime sleepiness. These drugs are useful for people who can manage wakefulness with a night's sleep and scheduled naps. They can improve mood, mental acuity, and other aspects of mental functioning. However, the evidence to support their benefit for patients with narcolepsy is not a strong as with modafinil.
Stimulants can have unpleasant side effects, including:
People with heart disease, hyperthyroidism, glaucoma, anxiety disorder, and high blood pressure should avoid stimulants, or take them only with a doctor's supervision.
These drugs become ineffective if used continuously, and patients are advised to take a drug holiday one day a week or to withdraw gradually and resume treatment at a lower dose. Patients should not engage in activities that require being awake (such as driving) during withdrawal.
Sodium oxybate (Xyrem). Sodium oxybate (Xyrem), also referred to as gamma hydroxybutyrate (GHB), helps reduce the frequency of cataplexy attacks and improve daytime sleepiness. Patients need to take GHB for about 4 weeks before they notice significant benefits. It may take an additional 4 weeks for the drug to reach maximum effect. Food intake can affect the actions of GHB, so patients are advised to take it at a regular time after the evening meal.
The FDA has placed tight restrictions on the use of this drug. Although the drug appears to be effective and safe when used for narcolepsy, it has a history of illegal and "date-rape" use, with street names such as "Grievous Bodily Harm" or "Liquid Ecstasy." (Despite this name, GHB is not the same as "Ecstasy," a street drug with different effects.) In high doses, GHB can cause dependence over time. Education through the Xyrem Success Program may be valuable to patients and physicians.
Very serious side effects -- including seizures, coma, respiratory arrest, and death -- have been reported in people who abused GHB. Trials of Xyrem, however, have not reported these effects with the doses used in treatment for cataplexy.
Antidepressants. Antidepressant drugs are not approved for treatment of cataplexy, but they are commonly used to manage this condition. Unfortunately, there have been few studies conducted on antidepressant treatment of cataplexy, and there are little data on which type of antidepressant work bests.
Antidepressants used for cataplexy, hallucinations, sleep paralysis, and management of REM symptoms include:
Tricyclics were the first antidepressants used for cataplexy; they were also one of the first treatments for cataplexy. They can be helpful for some patients but have many unpleasant side effects, including dry mouth, constipation, and weight gain. Tricyclics can also lower blood pressure and cause disturbances in heart rhythm.
SSRIs have fewer side effects than tricyclics but may not work as well for cataplexy control. The most common side effects include nausea, drowsiness or insomnia, headache, weight gain, and sexual dysfunction.
Venlafaxine (Effexor) is a selective serotonin and norepinephrine reuptake inhibitor (SSNRI) that has shown promising results for treatment of cataplexy. Some patients with narcolepsy, and their doctors, report that venlafaxine seems to work best of all the antidepressants.
Monoamine Oxidase Inhibitors (MAOIs). Selegiline (Eldepryl, Movergan), also known as deprenyl, is an MAOI that blocks monoamine oxidase B, an enzyme that degrades dopamine. MAOIs may play a role in narcolepsy, but how much benefit this group of drugs provides is not well proven.
Selegiline has significant side effects:
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Reviewed By: Harvey Simon, MD, Editor-in-Chief, Associate Professor of Medicine, Harvard Medical School; Physician, Massachusetts General Hospital. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M. Health Solutions, Ebix, Inc.