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Medical Author:

John P. Cunha, DO, FACOEP

John P. Cunha, DO, FACOEP

John P. Cunha, DO, is a U.S. board-certified Emergency Medicine Physician. Dr. Cunha's educational background includes a BS in Biology from Rutgers, the State University of New Jersey, and a DO from the Kansas City University of Medicine and Biosciences in Kansas City, MO. He completed residency training in Emergency Medicine at Newark Beth Israel Medical Center in Newark, New Jersey.

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Medical Editor:

William C. Shiel Jr., MD, FACP, FACR

William C. Shiel Jr., MD, FACP, FACR

Dr. Shiel received a Bachelor of Science degree with honors from the University of Notre Dame. There he was involved in research in radiation biology and received the Huisking Scholarship. After graduating from St. Louis University School of Medicine, he completed his Internal Medicine residency and Rheumatology fellowship at the University of California, Irvine. He is board-certified in Internal Medicine and Rheumatology.

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In this Article

• What is narcolepsy?
• How common is narcolepsy?
• What causes narcolepsy?
• What are the symptoms of narcolepsy?
• Excessive daytime sleepiness (EDS)
• Cataplexy
• Hypnagogic hallucinations
• Sleep paralysis
• Additional symptoms
• How is narcolepsy diagnosed?
• How is narcolepsy treated?
• Medications
• Non-drug treatments
• What is the outcome (prognosis) for patients with narcolepsy?
• What's in the future for narcolepsy?
• Narcolepsy At A Glance
• For more information
• Patient Comments: Narcolepsy - Excessive Daytime Sleepiness
• Patient Comments: Narcolepsy - Treatments
• Patient Comments: Narcolepsy - Experience
• Find a local Sleep Specialist in your town
• Narcolepsy Index

Advances have been made in the last few years in determining the cause of narcolepsy. The newest discovery has been the finding of abnormalities in the structure and function of a particular group of nerve cells, called hypocretin neurons, in the brains of patients with narcolepsy. These cells are located in a part of the brain called the hypothalamus and they normally secrete neurotransmitter substances (chemicals released by nerve cells to transmit messages to other cells) called hypocretins.

Abnormalities in the hypocretin system may be responsible for the daytime sleepiness and abnormal REM sleep found in narcolepsy. (See the section below on sleep laboratory tests for a discussion of REM sleep.)

Experiments in dogs and mice with narcolepsy point to an abnormal hypocretin system as a cause for the development of their narcolepsy. People with narcolepsy have been found to have a markedly decreased number of hypocretin nerve cells in the brain. They also have a decreased level of hypocretins in the cerebrospinal fluid (the fluid that surrounds the brain and the spinal cord).

Narcolepsy is associated with a specific type of human leukocyte antigen (HLA). HLAs are genetically determined proteins on the surface of white blood cells. They are a part of the body's immune (defense) system. The finding of a very high HLA-association in narcolepsy led to the proposal that narcolepsy is an autoimmune disease, similar to other HLA-associated diseases such as multiple sclerosis and ankylosing spondylitis.

It is theorized that an autoimmune reaction causes the loss of nerve cells in the brain in patients with narcolepsy. The environment (for example, infection or trauma) might trigger an autoimmune reaction where normal brain cells are attacked by the body's own immune system. As a result, the neurons are damaged and ultimately destroyed, and they and their neurotransmitter chemicals disappear. Whether narcolepsy is an autoimmune disease remains to be proven.

The role of heredity in humans with narcolepsy is not completely understood. No consistent pattern of heredity has been recognized in families so far. It is estimated that relatives of patients with narcolepsy may have a higher predisposition to develop narcolepsy or sleep-related abnormalities, such as increased daytime sleepiness, increased REM sleep, or others. In dogs with narcolepsy, the disease is inherited in a predictable pattern. In these animals, the narcolepsy is caused by a mutation in a particular gene that is normally responsible for producing a receptor (binder) in the brain for the hypocretin neurotransmitter.