Idiopathic hypersomnia is excessive sleeping (hypersomnia) without an obvious cause. It is different from narcolepsy in that idiopathic hypersomnia does not involve suddenly falling asleep or losing muscle control associated with strong emotions (cataplexy).

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 often develop slowly during adoescence 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, low energy, restlessness, slow thinking or speech, loss of appetite, and memory difficulty.

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

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

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

A psychiatric evaluation for atypical depression may also be done.

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
• Avoiding operating motor vehicles or using dangerous equipment
• Avoiding working at night or social activities that delay bedtime