Narcolepsy

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Narcolepsy is a disorder characterized by excessive daytime sleepiness. People with narcolepsy often fall asleep without warning at inappropriate times. These sleep attacks occur even after getting enough sleep at night. They can occur during driving, eating, or other activities and can cause accidents and injuries, problems at work and school, impaired memory or concentration and depression. Narcolepsy can affect schooling, work, and social life.


Contents

Signs and Symptoms

The major symptom of narcolepsy is excessive daytime sleepiness accompanied by sleep attacks. People with narcolepsy may also have one or more of the following signs and symptoms:

  • Sudden loss of muscle tone and control when awake (cataplexy). This can appear as muscle weakness and sometimes triggers the body to collapse. Up to 70% of narcolepsy cases are characterized by this symptom.[1]
  • Inability to move or speak while falling asleep or waking up (sleep paralysis).
  • Vivid dreams while falling asleep or waking up (hypnagogic hallucinations, which are different from the hallucinations experienced in schizophrenia).

Daytime sleepiness

Narcolepsy always causes excessive daytime sleepiness. This is usually the first symptom of the condition. Sudden, irresistible urges to sleep during the day (sleep attacks) are very common. Usually these attacks last just a few seconds or minutes. Rarely, they last as long as an hour or more. Daytime sleepiness can cause the following:

  • Mental cloudiness or fogginess
  • Memory problems
  • Problems focusing
  • Lack of energy
  • Depression
  • Exhaustion

Cataplexy

Nearly three out of four people with narcolepsy (75%) experience sudden muscle weakness while awake. This is called cataplexy. It is similar to the paralysis that occurs during dream sleep. Below are some consequences of mild attacks of muscle weakness:

  • Head nodding
  • Drooping eyelids
  • Difficulty speaking
  • Difficulty moving arms or hands, or a weakened grip
  • Buckling of the knees

Severe attacks of narcolepsy may cause complete paralysis and falls. Attacks often last less than two minutes. They can be as short as a few seconds. During both mild and severe attacks, consciousness is maintained.

The sudden attacks of muscle weakness in narcolepsy can happen at any time. These attacks are often triggered by the strong emotions listed below:

  • Laughter
  • Anger
  • Fear
  • Excitement

Attacks of muscle weakness and loss of muscle tone are sometimes the first symptoms that are noticed. However, usually these symptoms occur weeks or months after the onset of excessive daytime sleepiness.

{{#ev:youtube|VlVUV3pKz_I}} This YouTube video from Discovery Science shows a young girl with cataplexy.

Sleep paralysis

Narcolepsy often prevents movement and speech while falling asleep or waking up. This sleep paralysis occurs without loss of consciousness. The paralysis usually lasts just a few seconds or minutes, but it can be scary. Sleep paralysis is similar to the paralysis that happens in REM sleep. Not all people with narcolepsy have sleep paralysis.

Hypnagogic hallucinations

Some people with narcolepsy have vivid dreams while they are falling asleep, waking up, or dozing. These are called hypnagogic hallucinations, and they differ from normal dreams because they seem very real and include sights, sounds, smells, tastes, and touch. They are also different from hallucinations experienced by people suffering from schizophrenia; hypnagogic hallucinations occur only while falling asleep or waking up, whereas schizophrenic hallucinations occur while a person is fully awake. These hallucinations are often described as very scary, much like a nightmare. The hallucinations can occur with sleep paralysis.

Other symptoms

Paradoxically, narcolepsy may prevent some people from sleeping throughout the night. Frequent awakenings may start years after experiencing the first symptoms of narcolepsy. Another symptom of narcolepsy is performing actions without awareness. This is called automatic behavior. For example, this behavior may cause a person to scribble rather than form words when writing, or become lost or get into an accident while driving because the driver forgets she is driving. People usually do not remember such automatic behavior.

Causes

Crystal Structure Of Hla-Dq0602 In Complex With A Hypocretin Peptide. Source: National Institutes of Health.

The two types of sleep are rapid eye movement (REM) sleep and nonrapid eye movement (NREM) sleep. During REM sleep, the eyes move rapidly even though the eyelids remain closed. Dreaming mostly occurs during REM sleep. The body becomes limp and the muscles are unable to move. This temporary paralysis prevents acting out any dreams that may be occurring.

Normally, NREM sleep occurs first, followed by a cycle of REM sleep. People with narcolepsy have a different sleep pattern. They often fall into REM sleep before NREM sleep. Also, the boundary between being asleep and being awake is blurred. Elements of REM sleep happen during a period of wakefulness. This can lead to cataplexy, sleep paralysis, and hypnagogic hallucinations.

Research suggests that narcolepsy is caused by a lack of a protein called hypocretin, also called orexin, in the brain. [2] This chemical stimulates brain cells and helps promote wakefulness. It is not known why hypocretin is low in people who have narcolepsy. Below are some factors that may work in combination to cause low hypocretin levels:

  • Infection
  • Loss of key brain cells due to brain injury, toxins (chemicals that are poisonous to the body), and/or the body's destruction of its own tissues (autoimmune reaction)
  • Hormone changes
  • Stress

One out of ten people with narcolepsy and cataplexy has a close relative with the same symptoms. This suggests that some people may inherit the tendency to develop narcolepsy. [3]

Diagnosis

Doctors diagnose narcolepsy based on history of symptoms, family history of narcolepsy, physical exam, and test results. Symptoms are often distinct enough to make the diagnosis without needing further tests. When the diagnosis is unclear, laboratory tests are sometimes used for confirmation and determine the best treatment. These tests may require the patient to visit a sleep disorders center for an overnight evaluation.

History

If a patient reports a history of narcolepsy symptoms, a history is taken. Important questions included when the symptom(s) began, and if they interfere with sleep or daily activities. The doctor may also ask questions about sleep habits and how the person feels and acts during the daytime. Sleep diaries help to record symptoms. Information in sleep diaries that can help aid diagnosis include the following:

  • When one goes to bed and gets up
  • How long it takes to fall asleep, and how often one wakes up during the night
  • If a person snores loudly and frequently, or wakes up gasping or feeling out of breath
  • How refreshed one feels upon waking, and if the person feels tired during the day
  • How often the person dozes off or has trouble staying awake during the day

Doctors also take into account a family history of narcolepsy, and try to eliminate other sources of disturbed sleep.

Physical exam

Physical exams can eliminate symptoms caused by conditions other than narcolepsy. Several conditions mimic narcolepsy:

  • Infections
  • Certain thyroid diseases
  • Drug or alcohol use
  • Other medical or sleep disorders

Sleep specialists

Sleep specialist are often consulted to recommend special sleep tests, as described by the U.S. Department of Health & Human Services. Sleep specialists can confirm the diagnosis of narcolepsy, diagnose another sleep disorder, or rule out a specific sleep disorder as the cause of the symptoms. The results of sleep tests, recordings in sleep diaries, and the symptoms help determine a proper diagnosis.

Narcolepsy is easier to diagnose if there are more symptoms than just daytime sleepiness and sleep attacks.

Several sleep studies, performed in a clinic, can help diagnose narcolepsy.

Sleep tests

Sleep tests are usually done at a sleep disorders center. Some sleep tests are performed overnight, whereas other sleep tests can be done during the day. Narcolepsy is diagnosed using three sleep tests:

  • Polysomnogram (PSG)
  • Multiple sleep latency test (MSLT)
  • Hypocretin test

Polysomnogram

This study is performed during an overnight stay at a clinic. While sleeping, various devices are used to measure brain activity, breathing, and body movements. This test detects the tendency to fall asleep quickly, REM movement soon after falling asleep, and waking up often during the night.

Multiple sleep latency test

This test is usually done during the day after an overnight PSG. Also called a nap study, the MSLT measures how easy it is for the patient to fall asleep during the day. Patients take short naps about every two hours. The test records eye movements, muscle tone, and brain activity with small devices attached to the head. This test detects the tendency to quickly falling asleep during the day (after a full night's sleep) and REM sleep soon after falling asleep.

Hypocretin test

This test measures the levels of hypocretin in the fluid that bathes the spinal cord. Low levels of hypocretin suggest narcolepsy. The test requires a spinal tap, in which a needle is inserted into the sack that surrounds the spinal cord in order to obtain a sample of spinal fluid. This test can be painful, and there is a small risk of infection. The most common side effect of a spinal tap is a headache.

Treatment

Narcolepsy doesn’t have a cure. Many symptoms can be relieved with medicines and lifestyle changes. Treatment for narcolepsy is based on the type and severity of symptoms. Some medicines help relieve daytime sleepiness, while others help prevent the sudden loss of muscle tone and movement, or vivid dreams while falling asleep or waking up. Not all medicines work for everyone. It may take weeks to months to find the best treatment.

Medications

Medicines target both the daytime sleepiness of narcolepsy as well as other symptoms. Doctors may prescribe stimulants to increase daytime alertness. Below are some frequently used stimulants:

Modafinil is the newest stimulant for treating daytime sleepiness in people with narcolepsy. It may not be strong enough to relieve sleepiness in everyone with narcolepsy. It is sometimes prescribed with another stimulant to give more complete relief from daytime drowsiness.

Antidepressants can be used to treat the sudden loss of muscle tone, vivid dreams, or sleep paralysis associated with narcolepsy. These medicines affect the chemicals in the brain that play a role in narcolepsy. People with cataplexy may need to try several treatments before finding an effective medicine.

Lifestyle changes

Treatment is often more effective if drugs are combined with lifestyle changes. Short naps during times of excessive daytime sleepiness sometimes reduce the need for medication.

Other lifestyle modifications that are effective in narcolepsy include going to sleep and waking up at the same time each day, getting at least eight hours of sleep, and other good sleep habits. Several strategies can help one fall asleep at bedtime:

  • Doing something relaxing before bedtime, such as taking a warm bath.
  • Keeping the bedroom or sleep area quiet, comfortable, and free of light and distractions, such as a TV or a computer.
  • Exercising regularly, but not within three hours of bedtime.
  • Avoiding drugs such as caffeine, tobacco, alcohol, and some prescription medications within a few hours of going to bed

Living With Narcolepsy

Narcolepsy is a lifelong condition. Although there is no cure, symptoms often improve with ongoing treatment. Most people with narcolepsy can live near-normal lives. The condition can be dangerous if sleep attacks or sudden loss of muscle tone occur while driving or using machinery. Even when these episodes occur at other times, they can cause injury or impair performance in school and on the job. The following may help to avoid harm during sleep attacks:

  • Avoiding being alone when one is likely to have a sleep attack.
  • Taking a nap before times of the day when an attack is likely.
  • Safeguarding the home and workspace.
  • Seeking help from family, friends, coworkers, and a doctor.
  • Taking narcolepsy medicine on a regular schedule.

Driving

Driving can be dangerous for people with narcolepsy. Several precautions reduce the risk of an accident while driving:

  • Taking medicines as prescribed.
  • Asking a doctor if it is advisable to drive.
  • Planning to drive when a sleep attack or other narcolepsy symptoms is least likely.
  • Taking naps before driving.
  • Stopping regularly during a long drive and exercising during the stops.
  • Driving with family, friends, or coworkers or getting rides from them.

Work

People with narcolepsy can work in almost all types of jobs. Flexible work schedules that allow napping when needed are preferable. Having a job that involves interaction with other people also helps to maintain wakefulness. Jobs that require driving or long commutes to work increase the risk of attacks and accidents.

The Americans with Disabilities Act (ADA), [4] protects the employment rights of people who have disabilities, including narcolepsy. The ADA requires employers to reasonably accommodate the needs of their workers with disabilities. For workers with narcolepsy, these accommodations may include the following:

  • Allowing short naps during the work day
  • Adjusting work schedules around sleepy periods
  • Alterations to the workspace or job duties

Workers must tell their employer that they have narcolepsy to get these accommodations.

Employers with more than 50 workers are also covered by the Family and Medical Leave Act. This law allows employees pre-approved leave without pay to care for themselves or a family member with narcolepsy. The Social Security Disability Insurance or Supplemental Security Income programs may also help if narcolepsy prevents one from working.

School-aged children

Narcolepsy symptoms can affect learning because it limits children's ability to study, focus, and remember. Children with narcolepsy are sometimes mistakenly thought to have a learning disability or a seizure disorder like epilepsy. When tired, some children with narcolepsy speed up their activities, rather than slow down. These children can be mistakenly labeled as hyperactive. Teachers, school administrators, and school nurses can help a child with narcolepsy function effectively. Some schools have special education programs for children with narcolepsy.

Finding emotional support

Sudden sleep attacks or loss of muscle tone can be embarrassing. This can cause one to avoid get-togethers with friends, schoolmates, or fellow workers. It can cause low self-esteem. People with narcolepsy may also feel that they have no control over their behavior. This may lead to depression. The following may help in getting emotional support for narcolepsy:

  • Working with a doctor to better manage symptoms and emotional problems.
  • Changing one's lifestyle to minimize symptoms.
  • Learning about narcolepsy, and telling family and friends about the condition.
  • Seeking professional counseling.
  • Getting involved with patient support groups

Chances of Developing Narcolepsy

Narcolepsy may affect 150,000 (1 in 2,000) people or more in the United States. It usually first occurs between the ages of 15 and 30 and affects both men and women. The symptoms can start suddenly or appear gradually. The condition is difficult to diagnose without medical tests. Often people live with mild symptoms, such as daytime sleepiness and muscle weakness, for several years before narcolepsy is diagnosed. Narcolepsy can also develop later in life and even in children, but it is rare before the age of five years. Many factors increase the risk of developing narcolepsy:

  • A brother, sister, or parent with narcolepsy
  • Certain thyroid disorders
  • Diabetes
  • Autoimmune disorders (disease in which the body's infection fighting system mistakenly attacks the body's own organs and tissues)

Clinical Trials

Research

  • An article from 2000 in Neuroendocrinology proposed a relationship between decreased hypocretin levels in narcolepsy and disorders of metabolism. Leptin is a hormone which sends signals to the brain about the level of adipose (fat) tissues. The level of leptin was also decreased in narcolepsy sufferers in the study, suggesting a relationship between the increased BMI and narcolepsy patients. [5] A more recent study [6] did not show a decrease in leptin levels with narcolepsy.
  • The effect of environmental factors on the development of narcolepsy is also being studied. A 2007 article in Neuroepidemiology showed a possible link between flu or unexplained fever and narcolepsy. [7]

Notable Experts

Many research studies emerge from Stanford University's Center of Excellence for the Diagnosis and Treatment of Sleep Disorders. The Center for Narcolepsy was established in the 1980s and treats many patients with narcolepsy. The web site lists a contact for ongoing research studies involving narcolepsy. Stanford researchers identified the mutations on the hypocretin genes (in dogs) that appear to cause narcolepsy. [8]

Etymology

The term narcolepsy is derived from the French term narcolepsie. It is a combination of the Greek word narke, meaning numbness and stupor, and lepsis, which means attack or seizure.

References

  1. Baker MJ. eMedicine. Narcolepsy.
  2. Peyron C, Faraco J, Rogers W, et al. A mutation in a case of early onset narcolepsy and a generalized absence of hypocretin peptides in human narcoleptic brains. Nature Medicine. 2000 Sep;6(9):991-7. Abstract
  3. Ohayon M. From wakefulness to excessive sleepiness: what we know and still need to know. Sleep Med Rev. 2008 Apr;12(2):129-41. Abstract
  4. Americans with Disabilities Act: ADA Home Page
  5. Schulda A, Blumb W, Uhra M, Haacka M, Krausa T, Holsboera F, Pollmächera T. Reduced Leptin Levels in Human Narcolepsy. Neuroendocrinology. 2000 Oct;72(4):195-8. Abstract
  6. Dahmen N, Engel A, Helfrich J, Manderscheid N, Lobig M, Forst T, et al. Peripheral leptin levels in narcoleptic patients. Diabetes Technol Ther. 2007 Aug;9(4):348-53. Abstract
  7. Picchioni D, Hope CR, Harsh JR. A case-control study of the environmental risk factors for narcolepsy. Neuroepidemiology. 2007;29(3-4):185-92. Epub 2007 Nov 27. Abstract
  8. Hungs M, Fan J, Lin L, Lin X, Maka RA, Mignot E. Identification and functional analysis of mutations in the hypocretin (orexin) genes of narcoleptic canines. Genome Res. 2001 Apr;11(4):531-9. Abstract | PDF

External Links

National Sleep Foundation

Narcolepsy Network, Inc.

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