Narcolepsy

Alternative Names

Daytime sleep disorder; Cataplexy

Causes, incidence, and risk factors

Narcolepsy is a nervous system disorder. The exact cause is unknown.

In some patients, narcolepsy is linked to reduced amounts of a protein called hypocretin, which is made in the brain. What causes the brain to produce less of this protein is unclear.

There is a possibility that narcolepsy is an autoimmune disorder. An autoimmune disorder is when the body's immune system mistakenly attacks healthy tissue.

Narcolepsy tends to run in families. Certain genes are linked to narcolepsy.

Symptoms

Narcolepsy symptoms usually first occur during ages 15 to 30.

The most common symptoms are:

• Periods of extreme drowsiness during the day. You may feel a strong urge to sleep, often followed by a short nap (sleep attack).
  • These periods last for about 15 minutes each, although they can be longer.
  • They may happen after eating, while driving, talking to someone, or during other situations.
  • Most often, you wake up feeling refreshed.
• Dream-like hallucinations between sleep and wakefulness. They involve seeing or hearing, and possibly other senses.
• Sleep paralysis. This is when you cannot move as you start falling asleep or when you first wake up. It may last up to 15 minutes.
• Cataplexy. This is a sudden loss of muscle tone while awake that makes you unable to move. Strong emotions, such as laughter or anger, can trigger this.
  • Most attacks last for less than 30 seconds and can be missed.
  • Your head will suddenly fall forward, your jaw will become slack, and your knees will buckle.
  • In severe cases, a person may fall and stay paralyzed for as long as several minutes.

Signs and tests

The doctor will perform a physical exam and order blood work to rule out conditions that can cause similar symptoms. Conditions that can cause excessive sleepiness include:

• Insomnia and other sleep disorders
• Restless leg syndrome
• Seizures
• Sleep apnea
• Other medical, psychiatric, or nervous system diseases

Other tests may include:

• ECG (measures the heart's electrical activity)
• EEG (measures the brain's electrical activity)
• Genetic testing to look for narcolepsy gene
• Sleep study (polysomnogram)
• Multiple Sleep Latency Test (MSLT) to see how long it takes you to fall asleep during a daytime nap. Patients with narcolepsy fall asleep much faster than people without the condition.

Treatment

There is no known cure for narcolepsy. The goal of treatment is to control symptoms.

Lifestyle changes and emotional counseling may help you do better in work and social activities. This involves:

• Eating light or vegetarian meals during the day and avoiding heavy meals before important activities
• Planning naps to control daytime sleep and reduce the number of unplanned, sudden sleep attacks
• Scheduling a brief nap (10 to 15 minutes) after meals, if possible
• Telling teachers and supervisors about the condition so you are not punished for being "lazy" at school or work

You may need to take prescription medications to help you stay awake. The stimulant drug armodafinil is usually tried first. It is much less likely to be abused than other stimulants. Other stimulants include dextroamphetamine (Dexedrine, DextroStat) and methylphenidate (Ritalin).

Antidepressant medications can help reduce episodes of cataplexy, sleep paralysis, and hallucinations. Antidepressants include:

• Selective norepinephrine reuptake inhibitors (SNRIs) such as venlafaxine
• Selective serotonin reuptake inhibitors (SSRIs) such as fluoxetine, paroxetine, or citalopram
• Tricyclic antidepressants such as protriptyline or imipramine

Sodium oxybate (Xyrem) is prescribed to some patients for use at night.

If you have narcolepsy, you may have driving restrictions. Restrictions vary from state to state.

Expectations (prognosis)

Narcolepsy is lifelong (chronic) condition.

It is not deadly, but it may be dangerous if episodes occur during driving, operating machinery, or similar activities.

Narcolepsy can usually be controlled with treatment. Treating other underlying sleep disorders can improve symptoms of narcolepsy.

Complications

• Difficulty functioning at work
• Difficulty with social activities
• Injuries and accidents, if attacks occur during activities
• Side effects of medications used to treat the disorder

Calling your health care provider

Call your health care provider if:

• You have symptoms of narcolepsy
• Narcolepsy does not respond to treatment, or you develop other symptoms

Prevention

There is no known way to prevent narcolepsy. Treatment may reduce the number of attacks. Avoid situations that aggravate the condition if you are prone to attacks of narcolepsy.

References

Biller J, Love BB, Schneck MJ. Sleep and its disorders. In: Bradley WG, Daroff RB, Fenichel GM, Jankovic J, eds. Neurology in Clinical Practice. 5th ed. Philadelphia, Pa: Butterworth-Heinemann Elsevier; 2008:chap 72.

Mahowald MW. Disorders of sleep. In: Goldman L, Schafer AI, eds. Cecil Medicine. 24th ed. Philadelphia, Pa: Saunders Elsevier; 2011:chap 412.