Idiopathic hypersomnia is sleeping too much (hypersomnia) without an obvious cause. It is different from narcolepsy, because idiopathic hypersomnia does not involve suddenly falling asleep or losing muscle control due to strong emotions (cataplexy).A.D.A.M.

Causes, incidence, and risk factors

The usual approach is to consider other potential causes of excessive daytime sleepiness.

Other sleep disorders that may cause daytime sleepiness include:

• Isolated sleep paralysis
• Narcolepsy
• Obstructive sleep apnea
• Restless leg syndrome

Other causes of excessive sleepiness include:

• Atypical depression
• Certain medications
• Drug and alcohol use
• Low thyroid function (hypothyroidism)
• Previous head injury

Symptoms

Symptoms often develop slowly during adolescence or young adulthood. They include:

• Daytime naps that do not relieve drowsiness
• Difficulty waking from a long sleep -- may feel confused or disoriented
• Increased need for sleep during the day -- even while at work, or during a meal or conversation
• Increased sleep time -- up to 14 - 18 hours per day

Other symptoms may include:

• Anxiety
• Feeling irritated
• Loss of appetite
• Low energy
• Restlessness
• Slow thinking or speech
• Trouble remembering

Cataplexy -- suddenly falling asleep or losing muscle control -- which is part of narcolepsy, is NOT a symptom of idiopathic hypersomnia.

Signs and tests

The health care provider will take a detailed sleep history. Tests may include:

• Multiple-sleep latency test
• Sleep study (polysomnography, to identify other sleep disorders)

A psychiatric evaluation for atypical depression may also be done.

Treatment

Idiopathic hypersomnia is usually treated with stimulant medications such as amphetamine, methylphenidate, and modafinil. These drugs may not work as well for this condition as they do for narcolepsy.

Important lifestyle changes that can help ease symptoms and prevent injury include:

• Avoiding alcohol and medications that can make the condition worse
• Avoiding operating motor vehicles or using dangerous equipment
• Avoiding working at night or social activities that delay bedtime

References

1. Consens FB, Chervin RD. Sleep Disorders. In: Goetz, CG, ed. Textbook of Clinical Neurology. 3rd ed. Philadelphia, Pa: Saunders Elsevier; 2007: chap 54.
2. Tsai SC. Excessive sleepiness. Clin Chest Med. 2010; 31:341-351. [PubMed: 20488292]

Review Date: 6/10/2011.

Reviewed by: Denis Hadjiliadis, MD, Assistant Professor of Medicine, Division of Pulmonary, Allergy and Critical Care, University of Pennsylvania, Philadelphia, PA. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc.