Narcolepsy

Definition

Narcolepsy is a chronic sleep disorder characterized by overwhelming daytime drowsiness and sudden attacks of sleep.

People with narcolepsy often find it difficult to stay awake for long periods of time, regardless of the circumstances. Narcolepsy can cause serious disruptions in your daily routine.

Some people mistakenly attribute symptoms of narcolepsy to depression, seizure disorders, fainting, simple lack of sleep, or other conditions that may cause abnormal sleep patterns.

Narcolepsy is a chronic condition that doesn't go away completely. Although there's no cure for narcolepsy, medications and lifestyle changes can help you manage the symptoms. And talking to others — family, friends, employer, teachers — can help you cope better with narcolepsy.

Symptoms

The signs and symptoms of narcolepsy include:

• Excessive daytime sleepiness. The primary characteristic of narcolepsy is overwhelming drowsiness and an uncontrollable need to sleep during the day. People with narcolepsy fall asleep without warning, anywhere and at any time. For example, you may suddenly nod off while at work or talking with friends. You may sleep for just a few minutes or up to a half-hour before awakening and feeling refreshed, but then you fall asleep again.

  In addition to sleeping at inappropriate times and places, you may also experience decreased alertness throughout the day. Excessive daytime sleepiness usually is the first symptom to appear and is often the most troublesome, making it difficult for you to concentrate and function fully.

• Sudden loss of muscle tone. This condition, called cataplexy, can cause a range of physical changes, from slurred speech to complete weakness of most muscles, and may last for a few seconds to a few minutes. Cataplexy is uncontrollable and is often triggered by intense emotions, usually positive ones such as laughter or excitement, but sometimes fear, surprise or anger. For example, your head may droop uncontrollably or your knees may suddenly buckle when you laugh.

  Some people with narcolepsy experience only one or two episodes of cataplexy a year, while others have numerous episodes each day. About 70 percent of people with narcolepsy experience cataplexy.

• Sleep paralysis. People with narcolepsy often experience a temporary inability to move or speak while falling asleep or upon waking. These episodes are usually brief — lasting one or two minutes — but they can be frightening. You may be aware of the condition and have no difficulty recalling it afterward, even if you had no control over what was happening to you.

  This sleep paralysis mimics the type of temporary paralysis that normally occurs during rapid eye movement (REM) sleep, the period of sleep during which most dreaming occurs. This temporary immobility during REM sleep may prevent your body from acting out dream activity. Not everyone with sleep paralysis has narcolepsy, however. Many people experience a few attacks of sleep paralysis, especially in young adulthood.

• Hallucinations. These hallucinations, called hypnagogic hallucinations, may take place when a person with narcolepsy falls quickly into REM sleep, as he or she does at sleep onset at night and periodically during the day, or upon waking. Because you may be semiawake when you begin dreaming, you experience your dreams as reality, and they may be particularly vivid and frightening.

Other characteristics
Other signs and symptoms of narcolepsy include restless nighttime sleep and occasional automatic behavior. During episodes of automatic behavior, you continue to function during sleep episodes — even talking and putting things away, for example — but you awaken with no memory of performing such activities, and you generally don't perform these tasks well. As many as 40 percent of people with narcolepsy experience automatic behavior. People with narcolepsy may also act out their dreams at night by flailing their arms or kicking and screaming.

The signs and symptoms of narcolepsy can begin anytime up to your 50s, but they most commonly begin between the ages of 10 and 25. Narcolepsy is chronic, which means signs and symptoms may vary in severity, but they never go away entirely.

Causes

The exact cause of narcolepsy isn't known. It's believed that genetics may play a role. But the larger influence may be a trigger, such as an infection, that leads to damage to certain brain cells important to sleep.

Normal sleep pattern vs. narcolepsy
The normal process of falling asleep begins with a phase called non-rapid eye movement (NREM) sleep. During this phase, your brain waves slow down considerably. After an hour or two of NREM sleep, your brain activity picks up again, and REM sleep begins. Most dreaming occurs during REM sleep.

In narcolepsy, however, you suddenly fall into REM sleep without first experiencing NREM sleep and at abnormal times, such as during the day. Also, some of the aspects of sleep that normally occur only during REM sleep, such as sudden lack of muscle tone, sleep paralysis and vivid dreams, occur at other times during sleep in people with narcolepsy.

The role of brain chemicals
Hypocretin is an important chemical in your brain that helps regulate staying awake and keeps REM sleep stable and occurring at the appropriate time during sleep. The cells that make hypocretin are severely damaged in narcolepsy. Because the cells are damaged, hypocretin is found in low levels in people with narcolepsy — lowest of all in those who experience cataplexy.

Exactly what causes the damage to hypocretin cells is not known. But it's thought that there's probably some factor such as an infection and an abnormal immune response that leads to the damage. Certain genetic markers are also more common in people who develop narcolepsy. If another family member has narcolepsy, it is slightly more likely you could develop it.

Research continues to focus on whether an abnormal gene may be responsible for narcolepsy or if the body's immune system may be involved in mistakenly attacking hypocretin-producing cells in the brain.

The low levels of hypocretin may even lead to the development of a diagnostic test for narcolepsy. Hypocretin is normally present in spinal fluid of people without the disorder, but is present in only very low levels in the spinal fluid of people with narcolepsy.

Treatments and drugs

There is no cure for narcolepsy, but medications and lifestyle modifications can help you manage the symptoms. Medications include:

• Stimulants. Drugs that stimulate the central nervous system are the primary treatment to help people with narcolepsy stay awake during the day. Modafinil (Provigil), a newer stimulant, isn't as addictive and doesn't produce the highs and lows often associated with older stimulants. Some people need treatment with methylphenidate (Ritalin) or various amphetamines. Although these medications are effective, they may cause side effects, such as nervousness and heart palpitations, and can be addictive.
• Antidepressants. Doctors often prescribe antidepressant medications, which suppress REM sleep, to help alleviate the symptoms of cataplexy, hypnagogic hallucinations and sleep paralysis. These medications include tricyclic antidepressants such as protriptyline (Vivactil) and imipramine (Tofranil) and selective serotonin reuptake inhibitors (SSRIs) such as fluoxetine (Prozac, Sarafem) and sertraline (Zoloft).
• Sodium oxybate (Xyrem). This medication controls cataplexy in people with narcolepsy. Sodium oxybate helps to improve nighttime sleep, which is often poor in narcolepsy. In high doses it may also help control daytime sleepiness, even though you take it only at night. However, because the use of this drug has been associated with serious side effects, such as trouble breathing during sleep, sleepwalking and bed-wetting, it's strictly regulated by the Food and Drug Administration.

If you have other health problems, such as high blood pressure or diabetes, ask your doctor how medications for existing conditions may interact with those taken for narcolepsy.

Certain over-the-counter drugs, such as allergy and cold medications, can cause drowsiness as a side effect. If you have narcolepsy, your doctor will likely recommend that you avoid taking these medications.

Medications to treat narcolepsy can help reduce your signs and symptoms, but they can't alleviate them entirely. Lifestyle changes also are an integral part of treating narcolepsy.

http://www.mayoclinic.com