What Is Narcolepsy?
Narcolepsy (NAR-ko-lep-se) is a disorder that causes periods of extreme daytime sleepiness. It also may cause muscle weakness.
Rarely, people who have this disorder fall asleep suddenly, even if they’re in the middle of talking, eating, or another activity. Most people who have narcolepsy also have trouble sleeping at night.
Narcolepsy also may cause:
- Cataplexy (KAT-a-plek-se). This condition causes a sudden loss of muscle tone while you’re awake. Muscle weakness can occur in certain parts of your body or in your whole body. For example, if cataplexy affects your hand, you may drop what you’re holding. Strong emotions often trigger this weakness. It may last seconds or minutes.
- Hallucinations (ha-lu-si-NA-shuns). These vivid dreams occur while falling asleep or waking up.
- Sleep paralysis (pah-RAL-i-sis). This condition prevents you from moving or speaking while waking up and sometimes while falling asleep. Sleep paralysis usually goes away within a few minutes.
The two main phases of sleep are nonrapid eye movement (NREM) and rapid eye movement (REM). Most people are in the NREM phase when they first fall asleep. After about 90 minutes of sleep, most people go from NREM to REM sleep.
Dreaming occurs during the REM phase of sleep. During REM, your muscles normally become limp. This prevents you from acting out your dreams. (For more information on sleep cycles, see the National Heart, Lung, and Blood Institute’s “Your Guide to Healthy Sleep.”)
People who have narcolepsy often fall into REM sleep quickly and wake up directly from it. This is linked to vivid dreams while waking up and falling asleep.
Hypocretin, a chemical in the brain, helps control levels of wakefulness. Most people who have narcolepsy have low levels of this chemical. What causes these low levels isn’t well understood.
Researchers think that certain factors may work together to cause a lack of hypocretin. Examples include heredity; brain injuries; contact with toxins, such as pesticides; and autoimmune disorders. (Autoimmune disorders occur when the body’s immune system attacks the body’s healthy cells.)
Narcolepsy affects between 50,000 and 2.4 million people in the United States. Symptoms usually begin during the teen or young adult years. Due to extreme tiredness, people who have narcolepsy may find it hard to function at school, work, home, and in social situations.
Narcolepsy has no cure, but medicines, lifestyle changes, and other therapies can improve symptoms. Research on the causes of narcolepsy and new ways to treat it is ongoing.
What Causes Narcolepsy?
Most people who have narcolepsy have low levels of hypocretin. This is a chemical in the brain that helps control levels of wakefulness. What causes these low hypocretin levels isn’t well understood.
- Researchers think that certain factors may work together to cause a lack of hypocretin. These factors may include:
- Heredity. Some people may inherit a gene that affects hypocretin. Up to 10 percent of people who have narcolepsy report having a relative with the same symptoms.
- Brain injuries due to conditions such as brain tumors or strokes.
- Contact with toxins, such as pesticides.
- Autoimmune disorders. These are conditions in which the body’s immune system attacks the body’s healthy cells. An example of an autoimmune disorder is rheumatoid arthritis.
Heredity alone doesn’t cause narcolepsy. You also must have at least one other factor, such as one of those listed above, to develop narcolepsy.
What Are the Signs and Symptoms of Narcolepsy?
The four major signs and symptoms of narcolepsy are extreme daytime sleepiness, cataplexy (muscle weakness) while awake, and hallucinations and sleep paralysis during sleep.
If you have narcolepsy, you may have one or more of these symptoms. They can range from mild to severe.
Extreme Daytime Sleepiness
All people who have narcolepsy have extreme daytime sleepiness. This is often the most obvious symptom of the disorder.
During the day, you may have few or many periods of sleepiness. Each period usually lasts 30 minutes or less. Strong emotions, such as laughter, anger, fear, or excitement, can bring on this sleepiness.
- People who have this symptom often complain of:
- Mental cloudiness or “fog”
- Memory problems or problems focusing
- Lack of energy or extreme exhaustion
Rarely, people who have narcolepsy have sleep episodes in which they fall asleep suddenly. This is more likely to happen when they’re not active—for example, while reading, watching TV, or sitting in a meeting.
However, sleep episodes also may occur in the middle of talking, eating, or another activity. Cataplexy also may occur at the same time.
This condition causes loss of muscle tone while you’re awake. Muscle weakness occurs in certain parts of your body or in your whole body.
Cataplexy may make your head nod or make it hard for you to speak. Muscle weakness also may make your knees weak or cause you to drop things you’re holding. Some people lose all muscle control and fall.
Strong emotions, such as laughter or excitement, often trigger this symptom. It usually lasts a few seconds or minutes. During this time, you’re usually awake.
Cataplexy may occur weeks to years after you first start to have extreme daytime sleepiness.
If you have narcolepsy, you may have vivid dreams while falling asleep, waking up, or dozing. These dreams can feel very real. You may feel like you can see, hear, smell, and taste things.
This condition prevents you from moving or speaking while falling asleep or waking up. However, you’re fully conscious (aware) during this time. Sleep paralysis usually lasts just a few seconds or minutes, but it can be scary.
Most people who have narcolepsy also don’t sleep well at night. They may have trouble falling and staying asleep. Vivid, scary dreams may disturb sleep. Not sleeping well at night worsens daytime sleepiness.
Rarely, people who fall asleep in the middle of an activity, such as eating, may continue that activity for a few seconds or minutes. This is called automatic behavior.
During automatic behavior, you’re not aware of your actions, so you don’t perform them well. For example, if you’re writing before falling asleep, you may scribble rather than form words. If you’re driving, you may get lost or have an accident. Most people who have this symptom don’t remember what happened while it was going on.
Children who have narcolepsy often have trouble studying, focusing, and remembering things. Also, they may seem hyperactive. Some children who have narcolepsy speed up their activities rather than slow them down.
How Is Narcolepsy Diagnosed?
It can take as long as 10 to 15 years after the first symptoms appear before narcolepsy is recognized and diagnosed. This is because narcolepsy is fairly rare. Also, many of the symptoms of narcolepsy are like symptoms of other illnesses, such as infections, depression, and sleep disorders.
Narcolepsy is sometimes mistaken for learning problems, seizure disorders, or laziness, especially in school-aged children and teens. When narcolepsy symptoms are mild, it’s even harder to diagnose.
Your doctor will diagnose narcolepsy based on your signs and symptoms, your medical and family histories, a physical exam, and results from tests.
Signs and Symptoms
Tell your doctor about any signs and symptoms of narcolepsy that you have. This is important because your doctor may not ask about them during a routine checkup.
Your doctor will want to know when you first had signs and symptoms and whether they bother your sleep or daily routine. He or she also will want to know about your sleep habits and how you feel and act during the day.
To help answer these questions, you may want to keep a sleep diary for a few weeks. Keep a daily record of how easy it is to fall and stay asleep, how much sleep you get at night, and how alert you feel during the day.
For a sample sleep diary, see the National Heart, Lung, and Blood Institute’s “Your Guide to Healthy Sleep.”
Medical and Family Histories
To learn about your medical and family histories, your doctor may ask whether:
- You’re affected by certain factors that can lead to narcolepsy. These include infection, brain injuries, contact with toxins (such as pesticides), or autoimmune disorders.
- You take medicines and which ones you take. Some medicines can cause daytime sleepiness. Thus, your symptoms may be due to medicine, not narcolepsy.
- You have symptoms of other sleep disorders that cause daytime sleepiness.
- You have relatives who have narcolepsy or who have signs or symptoms of the disorder.
Your doctor will examine you to see whether another condition is causing your symptoms. For example, infections, certain thyroid diseases, drug and alcohol use, and other medical or sleep disorders may cause symptoms similar to those of narcolepsy.
If your doctor thinks you have narcolepsy, he or she will likely suggest that you see a sleep specialist. This specialist may advise you to have special sleep studies to find out more about your condition.
Sleep studies usually are done at a sleep center. The results of two tests—a polysomnogram (PSG) and a multiple sleep latency test (MSLT)—are used to diagnose narcolepsy.
Polysomnogram. You usually stay overnight at a sleep center for a PSG. The test records brain activity, eye movements, breathing, heart rate, and blood pressure. This test can help find out whether you:
- Fall asleep quickly
- Go into rapid eye movement (REM) sleep soon after falling asleep
- Wake up often during the night
Multiple sleep latency test. This daytime sleep study measures how sleepy you are. It’s often done the day after a PSG. During the test, you relax in a quiet room for about 30 minutes. A technician checks your brain activity during this time. The test is repeated three or four times throughout the day.
An MSLT finds out how quickly you fall asleep during the day (after a full night’s sleep). It also shows whether you go into REM sleep soon after falling asleep.
Hypocretin test. This test measures the levels of hypocretin in the fluid that surrounds your spinal cord. Most people who have narcolepsy have low levels of hypocretin.
To get a sample of spinal cord fluid, a spinal tap (also called a lumbar puncture) is done. For this procedure, your doctor inserts a needle into your lower back area and then withdraws a sample of your spinal fluid.