Narcolepsy is a neurological disorder caused by the brain’s inability to regulate sleep-wake cycles normally. The main features of narcolepsy are fatigue and cataplexy. The disease is also often associated with sudden sleep attacks, insomnia, dream-like hallucinations, and a condition called sleep paralysis. Its prevalence in the developed world is approximately the same as that of multiple sclerosis or Parkinson’s disease . However, with increased public education about narcolepsy and physician training in the diagnosis and treatment of sleep disorders, these figures are expected to rise.
In order to understand the basics of narcolepsy, it is important to first review the features of “normal sleep.” Sleep happens in cycles. When we fall asleep, we initially enter a light stage of sleep and then progress into increasingly deeper stages. Both light and deep sleep stages are called non-REM (rapid eye movement) sleep. After about 90 minutes, we enter the first stage of REM sleep, which is the dreaming portion of sleep, and throughout the night we alternate between stages of REM and non-REM sleep. For people with narcolepsy, sleep begins almost immediately with REM sleep and fragments of REM occur involuntarily throughout the waking hours. When you consider that during REM sleep our muscles are paralyzed and dreaming occurs, it is not surprising that narcolepsy is associated with paralysis, hallucinations, and other dream-like and dramatically debilitating symptoms.
Despite the perception that people with narcolepsy are perpetually sleepy, they do not typically sleep more than the average person. Narcolepsy is considered a “state boundary” control abnormality. That is, narcolepsy patients sleep a normal amount but cannot control the timing of sleep.
Contrary to common beliefs, people with narcolepsy do not spend a substantially greater proportion of their time asleep during a 24-hour period than do normal sleepers. In addition to daytime drowsiness and uncontrollable sleep episodes, most individuals also experience poor sleep quality that can involve frequent waking during nighttime sleep, and other sleep disorders.
Narcolepsy affects both sexes equally and develops with age; symptoms usually first develop in adolescence or young adulthood and may remain unrecognized as they gradually develop. The instance of a familial connection with narcolepsy is quite small but a combination of genetic and environmental factors may be at the root of this sleep disorder.
Narcolepsy patients typically endure many years of daytime sleepiness before seeking treatment because sleepiness is not indicative of disease to most people. Yet the devastating potential
of this disorder is reflected in studies showing that narcoleptic patients are more accident-prone and have difficulty with interpersonal relationships.
Researchers believe that narcolepsy may be caused by a deficiency in hypocretin production in the brain. The results of one recent study, in which hypocretin was directly administered to the brain, suggest that using hypocretin derivatives may be an effective way to prevent cataplexy and improve wakefulness.
Causes Of Narcolepsy:
Narcolepsy may have several causes. Most people with narcolepsy have low levels of the neurotransmitter hypocretin, which promotes wakefulness. Neurotransmitters are chemicals that neurons produce to communicate with each other and to regulate biological processes.
Most cases of narcolepsy are sporadic, meaning the disorder occurs in individuals with no known family history of the disorder. But clusters in families sometimes occur—up to 10 percent of individuals diagnosed with narcolepsy with cataplexy report having a close relative with the same symptoms. In extremely rare cases, narcolepsy is caused by a genetic defect that prevents normal production of hypocretin molecules. While close relatives of people with narcolepsy have a statistically higher risk of developing the disorder than do members of the general population, that risk remains low when compared to diseases that are purely genetic in origin.
When cataplexy is present, the cause is most often the discrete loss of brain cells that produce hypocretin. Although the reason for such cell loss remains unknown, it appears to be autoimmune in nature (an autoimmune disorder is when the body’s immune system mistakenly attacks healthy cells or tissue). That is, the body’s immune system selectively attacks hypocretin-containing brain cells.
Other factors appear to play important roles in the development of narcolepsy. Some rare cases are known to result from traumatic injuries to parts of the brain involved in REM sleep or from tumor growth and other disease processes in the same regions. Infections, exposure to toxins, dietary factors, stress, hormonal changes such as those occurring during puberty or menopause, and alterations in a person’s sleep schedule are just a few of the many factors that may exert direct or indirect effects on the brain, thereby possibly contributing to disease development.
The main symptoms associated with narcolepsy are:
- Excessive daytime sleepiness – this is usually the first symptom to appear in people who have narcolepsy. Unless they’re being treated for the disorder, the need to sleep can be overwhelming for narcolepsy patients: someone who has narcolepsy is prone to falling asleep while engaged in conversation, driving, eating dinner, or at other inappropriate times. The sleepiness occurs in spite of a full night’s sleep and may persist throughout the day.
- Cataplexy – cataplexy is a sudden loss of muscle tone, usually triggered by emotional stimuli such as laughter, surprise, or anger. It may involve all muscles and result in collapse. It may only affect certain muscle groups and result in slurred speech, buckling of the knees, or weakness in the arms. Consciousness is maintained throughout the episode but the patient is usually unable to speak.
- Hypnagogic hallucinations – during transition from wakefulness to sleep, the patient has bizarre, often frightening dream-like experiences that incorporate his or her real environment.
- Sleep paralysis – a temporary inability to move during sleep-wake transitions. Sleep paralysis may last for a few seconds to several minutes and may accompany hypnagogic hallucinations.
- Disturbed nocturnal sleep – waking up repeatedly throughout the night.
- Leg jerks, nightmares, and restlessness.
Excessive daytime sleepiness (EDS)
EDS, the symptom most consistently experienced by almost all individuals with narcolepsy, is usually the first to become clinically apparent. Generally, EDS interferes with normal activities on a daily basis, whether or not individuals had sufficient sleep at night. People with EDS describe it as a persistent sense of mental cloudiness, a lack of energy, a depressed mood, or extreme exhaustion. Some people experience memory lapses, and many have great difficulty maintaining their concentration while at school, work, or home. People tend to awaken from such unavoidable sleeps feeling refreshed and finding that their drowsiness and fatigue subsides for an hour or two.
Involuntary sleep episodes are sometimes very brief, lasting no more than seconds at a time. As many as 40 percent of people with narcolepsy are prone to automatic behavior during such “microsleeps.” Automatic behavior involves performing a task during a short period of sleep but without any apparent interruption. During these episodes, people are usually engaged in habitual, essentially “second nature” activities such as taking notes in class, typing, or driving. They cannot recall their actions, and their performance is almost always impaired. Their handwriting may, for example, degenerate into an illegible scrawl, or they may store items in bizarre locations and then forget where they placed them. If an episode occurs while driving, individuals may get lost or have an accident.
EDS, the most common of all narcoleptic symptoms, can be the result of a wide range of medical conditions, including other sleep disorders such as sleep apnea, various viral or bacterial infections, mood disorders such as depression, and chronic illnesses such as anemia, congestive heart failure, and rheumatoid arthritis that disrupt normal sleep patterns. Some medications can also lead to EDS, as can consumption of caffeine, alcohol, and nicotine. Finally, sleep deprivation has become one of the most common causes of EDS among Americans.
Cataplexy is a sudden loss of muscle tone while the person is awake that leads to feelings of weakness and a loss of voluntary muscle control. Attacks can occur at any time during the waking period, with individuals usually experiencing their first episodes several weeks or months after the onset of EDS. But in about 10 percent of all cases, cataplexy is the first symptom to appear and can be misdiagnosed as a seizure disorder. Cataplectic attacks vary in duration and severity. The loss of muscle tone can be barely perceptible, involving no more than a momentary sense of slight weakness in a limited number of muscles, such as mild drooping of the eyelids. The most severe attacks result in a complete loss of tone in all voluntary muscles, leading to physical collapse during which individuals are unable to move, speak, or keep their eyes open. But even during the most severe episodes, people remain fully conscious, a characteristic that distinguishes cataplexy from seizure disorders. Although cataplexy can occur spontaneously, it is more often triggered by sudden, strong emotions such as fear, anger, stress, excitement, or humor. Laughter is reportedly the most common trigger.
The loss of muscle tone during a cataplectic episode resembles the interruption of muscle activity that naturally occurs during REM sleep. A group of neurons in the brain stem halts activity during REM sleep, inhibiting muscle movement. Using an animal model, scientists have learned that this same group of neurons becomes inactive during cataplectic attacks, a discovery that provides a clue to at least one of the neurological abnormalities contributing to human narcoleptic symptoms.
The temporary inability to move or speak while falling asleep or waking is similar to REM-induced inhibitions of voluntary muscle activity. This natural inhibition usually goes unnoticed by people who experience normal sleep because it occurs only when they are fully asleep and entering the REM stage at the appropriate time in the sleep cycle. The attacks usually last a few seconds or minutes. Experiencing sleep paralysis resembles undergoing a cataplectic attack affecting the entire body. As with cataplexy, people remain fully conscious. Even when severe, cataplexy and sleep paralysis do not result in permanent dysfunction—after episodes end, people rapidly recover their full capacity to move and speak.
Hallucinations can accompany sleep paralysis and occur when people are falling asleep, waking, or during sleep. Referred to as hypnagogic hallucinations when occurring during sleep onset and as hypnopompic hallucinations when occurring during waking, these images are unusually vivid, seem real, and can be frightening. Most often, the content is primarily visual, but any of the other senses can be involved.
Disrupted nocturnal sleep
While individuals with narcolepsy have no difficulties falling asleep at night, most experience difficulties staying asleep. Sleep may be disrupted by insomnia, vivid dreaming, sleep talking, acting out while dreaming, and periodic leg movements.
After developing narcolepsy, many individuals suddenly gain weight, a side effect that can be prevented by active treatment.
A clinical examination and exhaustive medical history are essential for diagnosis and treatment. Your doctor may ask you to keep a sleep journal noting the times of sleep and symptoms over a one-to-two-week period. Although none of the major symptoms is exclusive to narcolepsy, cataplexy is the most specific symptom and is rarely present outside of narcolepsy.
A physical exam can rule out or identify a condition that may be causing the symptoms. A battery of specialized tests, which can be performed in a sleep disorders clinic, is usually required before a diagnosis can be confirmed.
Two tests in particular are essential in confirming a diagnosis of narcolepsy: the polysomnogram (PSG) and the multiple sleep latency test (MSLT). The PSG is an overnight test that takes continuous multiple measurements while the individual is asleep to document abnormalities in the sleep cycle. It records heart and respiratory rates, electrical activity in the brain using electroencephalography, and nerve activity in muscles through electromyography. A PSG can help reveal whether REM sleep occurs at abnormal times in the sleep cycle and can rule out the possibility that an individual’s symptoms result from another condition.
The MSLT is performed during the day to measure a person’s tendency to fall asleep and to determine whether isolated elements of REM sleep intrude at inappropriate times during the waking hours. The sleep latency test measures the amount of time it takes for a person to fall asleep. As part of the test, an individual is asked to take four or five short naps usually scheduled 2 hours apart over the course of a day. Because sleep latency periods are normally 12 minutes or longer, a latency period of 8 minutes or less suggests a disorder of excessive daytime sleepiness. However, a sleep latency of 8 minutes or less can be due to many conditions other than narcolepsy. The MSLT also measures heart and respiratory rates, records nerve activity in muscles, and pinpoints the occurrence of abnormally timed REM episodes through EEG recordings. If a person enters REM sleep either at the beginning or within a few minutes of sleep onset during at least two of the scheduled naps, this is considered an indication of narcolepsy. Other reasons for REM sleep on the MSLT must be ruled out, such as the effects of medication and disrupted sleep from sleep apnea or an irregular work-rest schedule.
In some cases, human leukocyte antigen (HLA) typing (a marker of viral infection) may be helpful. Most HLA-associated disorders are autoimmune in nature. Certain alleles (genetic information found on a specific location on specific chromosomes) located on chromosome 6 are strongly associated with narcolepsy-cataplexy. To definitively identify a lack of hypocretin as the cause of narcolepsy, a sample of the cerebrospinal fluid (CSF) is removed by using a lumbar puncture and the level of hypocretin-1 is measured. When no other serious medical condition is present, low CSF hypocretin-1 can establish hypocretin deficiency as the cause of narcolepsy.
When cataplexy is not present, diagnosis must be made after excluding other possible causes of daytime sleepiness and fatigue, along with a positive MSLT.
In order to make a determination of narcolepsy, your doctor will ask you for a complete medical and family history and may refer you to a sleep center for evaluation. You should keep a sleep diary as well as a record of your symptoms and their severity for at least a week or two. Bring this information with you when you visit your doctor.
There is currently no widely-accepted cure for narcolepsy but symptoms can be alleviated to the point of near-normal functioning in many patients. Treatment for narcolepsy includes the use of medication as well as behavioral therapy.
Behavioral therapies may help control symptoms, including taking three or more scheduled naps throughout the day. Patients should also avoid heavy meals and alcohol, which can disturb or induce sleep.
Counseling is very important for people with narcolepsy. The particular symptoms of this disorder are not widely understood by the general public and this may cause patients to feel uncomfortable, alienated, or depressed. The disease can also be quite frightening and the fear of falling asleep inappropriately often significantly alters life for people with narcolepsy.
In treating narcolepsy, doctors typically prescribe stimulants to improve alertness and diminish excessive daytime sleepiness. Antidepressants are also often used to treat cataplexy, hypnagogic hallucinations and sleep paralysis. Finally, sodium oxybate, a strong sleep-inducing agent, may be given at night to improve disturbed nocturnal sleep and reduce daytime sleepiness and cataplexy. All these treatments may have side effects. Stimulants can cause headaches, irritability, mood changes, nervousness, insomnia, anorexia, and irregular heartbeat. Side effects from the use of antidepressants vary and can include nausea, weight gain, anxiety or decreased emotions, drowsiness, sexual dysfunction and changes in blood pressure. Sodium oxybate can induce nausea, excessive sedation, mood changes and enuresis.
The goal in using medications to treat narcolepsy is to achieve normal alertness with minimal side effects.
Narcolepsy cannot yet be cured, but some of the symptoms can be treated with medicines and lifestyle changes. When cataplexy is present, the loss of hypocretin is believed to be irreversible and life-long. But EDS and cataplexy can be controlled in most individuals with drug treatment. Modafinil and sodium oxybate are two drugs that have been approved by the U.S. Food and Drug Administration for the treatment of narcolepsy.
Doctors prescribe central nervous system alerting agents such as modafinil and amphetamine-like stimulants such as methylphenidate to alleviate EDS and reduce the incidence of sleep attacks. For most people these medications are generally quite effective at reducing daytime drowsiness and improving levels of alertness. However, use of these medications may be associated with several undesirable side effects and must be carefully monitored. Common side effects include irritability and nervousness, shakiness, disturbances in heart rhythm, stomach upset, nighttime sleep disruption, and anorexia. Individuals may also develop tolerance with long-term use, leading to the need for increased dosages to maintain effectiveness. In addition, doctors should be careful when prescribing these drugs and people should be careful using them because the potential for abuse is high with any amphetamine.
Two classes of antidepressant drugs have proved effective in controlling cataplexy in many individuals: tricyclics (including imipramine, desipramine, clomipramine, and protriptyline) and selective serotonin and noradrenergic reuptake inhibitors (including venlafaxine, fluoxetine and atomoxetine). In general, antidepressants produce fewer adverse effects than do amphetamines. But troublesome side effects still occur in some individuals, including impotence, high blood pressure, and heart rhythm irregularities.
In addition to central nervous system alerting agents and antidepressants, sodium oxybate or gamma hydroxybutyrate, also known as GHB or Xyrem®, can be used to treat narcolepsy. Sodium oxybate is a strong sedative that must be taken during the night. Sodium oxybate induces sleep and reduces the symptoms of daytime sleepiness and cataplexy. Due to safety concerns associated with the use of this drug, the distribution of sodium oxybate is tightly restricted.
Behavioral Strategies Help Cope With symptoms:
Currently available medications do not enable all people with narcolepsy to consistently maintain a fully normal state of alertness. Drug therapy should accompany various behavioral strategies according to the needs of the affected individual.
Many individuals take short, regularly scheduled naps at times when they tend to feel sleepiest.
Improving the quality of nighttime sleep can combat EDS and help relieve persistent feelings of fatigue.
Among the most important common-sense measures people can take to enhance sleep quality are:
- maintain a regular sleep schedule—go to bed and wake up at the same time every day
- avoid alcohol and caffeine-containing beverages for several hours before bedtime
- avoid large, heavy meals just before bedtime
- avoid smoking, especially at night
- maintain a comfortable, adequately warmed bedroom environment, and
- engage in relaxing activities such as a warm bath before bedtime.
Exercising for at least 20 minutes per day at least 4 or 5 hours before bedtime also improves sleep quality and can help people with narcolepsy avoid gaining excess weight.
Safety precautions, particularly when driving, are particularly important for all persons with narcolepsy. EDS and cataplexy can lead to serious injury or death if left uncontrolled. Suddenly falling asleep or losing muscle control can transform actions that are ordinarily safe, such as walking down a long flight of stairs, into hazards. People with untreated narcoleptic symptoms are involved in automobile accidents roughly 10 times more frequently than the general population. However, accident rates are normal among individuals who have received appropriate medication.
Support groups frequently prove extremely beneficial because people with narcolepsy may become socially isolated due to embarrassment about or misunderstandings related to their symptoms. Many people also try to avoid strong emotions, since humor, excitement, and other intense feelings can trigger cataplectic attacks. Support groups also provide individuals with a network of social contacts who can offer practical help and emotional support.
The Americans with Disabilities Act requires employers to provide reasonable accommodations for all employees with disabilities. Adults can often negotiate with employers to modify their work schedules so they can take naps when necessary and perform their most demanding tasks when they are most alert. Similarly, children and adolescents with narcolepsy may be able to work with school administrators regarding special needs, including medication requirements during the school day, and to modify class schedules.
It’s very common for those with narcolepsy to suffer from depression. Many symptoms of narcolepsy—particularly sleep attacks and cataplexy—can cause great embarrassment and wreak havoc on your ability to live a normal life. These episodes can be frightening, and you may become depressed because of the sudden lack of control. Fear of falling asleep or of sudden collapse forces some people to become reclusive and withdrawn. Reaching out to a psychologist, counselor, or narcolepsy support group can help you cope with the effects of the disorder.
Reaching out may seem overwhelming at first, but being with others who face the same problems can help reduce your sense of isolation and remove any stigma you may feel. It can also be inspiring to share experiences and learn how others have coped with his or her symptoms of narcolepsy.
Making healthy lifestyle changes can help you manage narcolepsy symptoms, in conjunction with counseling and support, and any recommendations from your doctor. Daytime habits—such as exercise, diet, and how you manage stress—play a large role in helping you maintain a healthy sleep-wake cycle. It’s important to follow a regular sleep schedule, a relaxing bedtime routine, and take practical steps to counter the effects of narcolepsy during the day.
Combining the various self-help treatments can help to not only improve your daytime alertness but also help reduce the symptoms of narcolepsy.
If you believe you are suffering from narcolepsy it is important to engage your health care team as the condition can be quite debilitation and wreak hazard on quality of life.