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Narcolepsy and Idiopathic Hypersomnia


Narcolepsy is associated with additional symptoms that help distinguish it from other sleep disorders, including idiopathic hypersomnia. Although excessive daytime sleepiness is the only symptom that is required to be present for a diagnosis of narcolepsy, the additional symptoms listed below are commonly present in narcolepsy and help make or confirm the diagnosis.

You may have narcolepsy if you experience some of the following symptoms:

  • Excessive Daytime Sleepiness - Excessive daytime sleepiness is usually the first symptom to appear and often the most disabling. Excessive sleepiness may include irresistible urges to sleep throughout the day. Narcoleptics have a tendency to easily nod off when inactive and have a higher risk of motor vehicle accidents. In addition, the excessive sleepiness may adversely affect a patient’s short-term memory and performance. Excessive sleepiness may be partially relieved by short “therapeutic” naps lasting from a few minutes to an hour.
  • Cataplexy - Cataplexy is a sudden loss of muscle tone specifically triggered by strong emotions such as laughter, startle or fear, and is a symptom that is only found in narcolepsy. The loss of muscle tone may range from slight weakness (head drop, arm weakness, slurred speech, or buckling knees) to total body collapse, during which time the narcoleptic may appear unconscious, even though the individual actually remains awake and alert. Cataplectic events can last from a few seconds to several minutes. Although patients with narcolepsy may experience cataplexy, many narcoleptics will never experience cataplexy.
  • Hypnagogic or hyponopompic hallucinations - One out of every two narcoleptics experience vivid, dream-like hallucinations called hypnagogic (from wake to sleep) or hypnopompic (from sleep to wake) hallucinations, which occur during the transitions between wakefulness and sleep. These hallucinations can vary from simple images to nightmare-like events.
  • Sleep paralysis - Narcoleptics may experience sleep paralysis at sleep onset or upon awakening, feeling unable to move or talk for a few seconds to several minutes even though they are awake and aware of their surroundings. Sleep paralysis can be very frightening, especially when combined with vivid hallucinations.
  • Disturbed night sleep and insomnia - Narcoleptics often experience frequent awakenings at night and difficulty maintaining sleep, but tend to have little problem initiating sleep. Such a disturbed sleep at night may be so prominent in some patients that they may have a primary complaint of sleep maintenance insomnia.

When should you suspect narcolepsy or idiopathic hypersomnia?
If you answer yes to the following questions, you may suspect narcolepsy or idiopathic hypersomnia and should consult a qualified sleep medicine physician. You may or may not experience all symptoms listed above, however it is important to seek help.

  1. Are you often overwhelmed by a feeling of sleepiness or falling asleep during the day?
  2. Do you struggle throughout the day, never feeling fully alert even though you had a full night of sleep?
  3. Do you feel still feel sleepy even though you recently had a long nap?


Narcolepsy and idiopathic hypersomnia are two different disorders that have excessive daytime sleepiness as a major symptom, and, in some cases, these disorders may be difficult to differentiate clinically. The cause of narcolepsy was recently discovered, whereas the cause of idiopathic hypersomnia remains unknown. Indeed, the term "idiopathic hypersomnia" actually means "sleepiness of unknown cause."

Narcolepsy is a neurological disorder, and it was recently discovered that a neurotransmitter system in the brain using hypocretin as a chemical messenger selectively degenerates in patients with narcolepsy. Usually, hypocretin neurons in the hypothalamus (region of the brain) help keep the brain awake. For reasons that are not yet clear, recent research has found that neurons containing hypocretin degenerate and die in narcoleptics. No other neurons in the brain, however, appear to be affected in such patients. As a result of the loss of these “waking neurons”, the level of alertness is decreased, and narcoleptics develop excessive daytime sleepiness. Once narcolepsy has developed in a patient, the degree of sleepiness tends be stable throughout the remainder of their lifetime. If narcoleptics develop worsening sleepiness later in life, it is generally caused by an independent problem or disorder, such as chronic sleep deprivation (lifestyle) or the onset of a different sleep disorder such as obstructive sleep apnea.

Idiopathic hypersomnia also is believed to be caused by pathology within the brain, but its cause has remained a mystery. Although the degree of pathologic sleepiness may be prominent, daytime sleepiness in patients with idiopathic hypersomnia is generally not as severe as in patients with narcolepsy.


It is believed that both genetic and non-genetic predisposing factors contribute to the development of narcolepsy. Narcolepsy equally affects both men and women. It usually starts during adolescence but the onset can start as early as five years of age or even after the age of 60. It affects roughly 130,000 Americans or about one out of every 2,000 people. Although narcolepsy is perceived as a relatively rare disorder, its prevalence is similar to multiple sclerosis. As noted above, researchers believe that narcolepsy is caused by a loss of the neuropeptide hypocretin in the brain. The loss of hypocretin containing neurons is believed to be due, in most cases, to an autoimmune cause.


The chronic course of the disease and the potentially devastating socioeconomic impact (diminished self-esteem, strained relationships, accidents, lost jobs, etc.) make narcolepsy a significant problem. Nodding off when relatively inactive can happen anytime or anywhere, while you read or talk, eat, or even drive, and can put your life and others in danger. Patients with narcolepsy should not drive a motor vehicle if untreated. However, narcoleptics have minimal restrictions as long as they seek and adhere to medical therapy. If events of everyday life such as joking, playing sports or even making love become intimidating because of excessive sleepiness or a potential of developing cataplexy, seek help and no longer feel the need to avoid such situations out of fear or embarrassment.


As a symptom, sleepiness is often confused with fatigue in the medical community. Fatigue is usually described as a feeling of low energy or malaise, whereas sleepiness is the actual propensity to fall asleep when inactive. Many medical conditions may cause fatigue, as in patients with thyroid disorders, depression or heart disease, but these other conditions are generally not associated with excessive sleepiness. That is, although patients with congestive heart failure may feel "fatigued," they typically will not nod off when sitting inactive (unless they also have a sleep disorder).

Because fatigue and sleepiness are terms that are often erroneously used interchangeably by the medical community, patients with narcolepsy often go through many years of experiencing symptoms before being properly diagnosed with a sleep disorder. Moreover, most physicians outside of sleep medicine have never seen a patient with cataplexy, and patients with cataplexy are often misdiagnosed with other disorders (such as epilepsy, depression, schrizophrenia, or syncope) before being properly diagnosed with narcolepsy. Therefore, it is critical for you to be evaluated by a qualified sleep medicine specialist who will conduct a clinical evaluation based on your symptoms and health history.

If your sleep medicine physician suspects narcolepsy, you will be asked to undergo an overnight polysomnogram (PSG) or sleep study and a Multiple Sleep Latency Test (MSLT) the following day to confirm the diagnosis or rule out other sleep disorders with similar symptoms. Various monitoring instruments are used during the sleep evaluation to monitor your brain activity, heart, muscles, eye movements, airflow and blood oxygen levels during sleep. The MSLT measures how fast you fall asleep during the day and the type of sleep you experience during naps.


Although no treatment can cure narcolepsy or idiopathic hypersomnia, your symptoms can be greatly improved through behavioral and drug therapy.

Behavioral Therapies
You may be recommended to take one or two short naps during the day and exercise regularly to promote alertness. You should also maximize your total sleep time at night, keep a regular sleep-wake schedule, and avoid heavy meals and alcohol, which may induce sleepiness. It may be helpful to educate family members, friends, or colleagues to avoid feeling embarrassed or misunderstood by your condition.

Medications that increase alertness are commonly used to treat narcolepsy and idiopathic hypersomnia. You should receive a tailored treatment plan so as to find the right balance between benefits and potential side effects.

  • Excessive Daytime Sleepiness resulting from narcolepsy or idiopathic hypersomnia is typically treated with a central nervous system stimulant. Numerous stimulants have long been available and are effective for improving excessive sleepiness. The more traditional medications include amphetamine-like stimulants (e.g. Ritalin, Dexedrine), but may cause side effects such headaches, irritability, anxiety, insomnia, anorexia, or irregular heartbeat or tachycardia. A newer wake-promoting drug called modafenil (Provigil and Nuvigil), is also commonly used. Modafinil is not a traditional amphetamine-like stimulant, but is also very effective in improving daytime alertness. Modafinil typically has less long-term side effects than older stimulants and is generally well tolerated. Some patients may develop a headache when first starting modafinil, which typically resolves once on a steady dose.
  • Cataplexy, hypnagogic hallucinations, and sleep paralysis may be treated with antidepressants such as protriptyline (Vivactil) or serotonin reuptake inhibitors.
  • Cataplexy and Excessive Daytime Sleepiness can also be treated with some antidepressant medications or with sodium oxybate (Xyrem). Xyrem is a relatively new medication available for narcolepsy with cataplexy. It is a liquid taken at bedtime and generally four hours later (in the middle of the night). It is very sedating, but short acting, meaning that patients typically do not have sleepiness or grogginess upon awakening the next morning. Xyrem has been demonstrated to improve nighttime quality of sleep, daytime alertness and cataplexy. Sedation and nausea are the most common side effects.

For More Information

For more information about narcolepsy, visit the American Academy of Sleep Medicine at http://www.sleepeducation.com, the National Sleep Foundation at http://www.sleepfoundation.org, the Narcolepsy Network at http://www.narcolepsynetwork.org, and the Stanford Center for Narcolepsy at http://med.stanford.edu/school/Psychiatry/narcolepsy/

narcolepsy, idiopathic hypersomnia, causes of narcolepsy, narcolepsy symptoms, narcolepsy treatment


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