Idiopathic hypersomnia is an uncommon sleep disorder that causes you to be very sleepy during the day even after a full night of good sleep. Its cause is unknown. It also often causes difficulty waking up after you've been asleep. If you take a nap, you generally don't feel refreshed and you may wake up confused and disoriented.

The need to sleep can strike at any time, including when you're driving a car or working, which makes idiopathic hypersomnia potentially dangerous.

The condition often develops gradually. Diagnosing idiopathic hypersomnia requires ruling out more-common sleep disorders. The aim of treatment is to control symptoms with medication.

Your health care provider will usually ask you about your symptoms and discuss your personal medical history to diagnose idiopathic hypersomnia. You'll also likely have a physical exam. You may have several tests to either diagnose your condition or rule out other conditions that may be causing your symptoms.

It's important to discuss your family history and what medicines you're taking. For a diagnosis of idiopathic hypersomnia, you must have experienced daily excessive sleepiness for at least three months.

These may also help diagnose idiopathic hypersomnia:

• Epworth Sleepiness Scale. Your health care provider may ask you to rate your sleepiness with this tool to help determine how sleep affects your daily life.
• Sleep diary. Your provider may ask you to keep a sleep diary. You log your daily sleep and wake times to help show your sleep patterns and how much you sleep.
• Polysomnogram. In this test, you stay in a sleep center overnight. A polysomnogram monitors your brain activity, eye movements, leg movements, heart rate, breathing functions and oxygen levels as you sleep.
• Multiple sleep latency test. You are given multiple daytime nap opportunities and during these naps, measurements show the types and stages of sleep you go through. This test is generally conducted the day after a polysomnogram.

Because the cause of idiopathic hypersomnia isn't known, the treatment is aimed at easing symptoms. Stimulant medication, such as modafinil (Provigil, Alertec), might be prescribed to help you stay awake during the day. Possible side effects of modafinil are headaches, dry mouth, nausea, diarrhea, loss of appetite and weight loss.

Other medicines suggested by the American Academy of Sleep Medicine are sodium oxybate (Xyrem), clarithromycin (Biaxin XL, Klaricid) and methylphenidate (Quillivant XR, Daytrana, QuilliChew ER).

Recently, a drug containing lower-sodium oxybate (Xywav) was approved by the U.S. Food and Drug Administration for the treatment of idiopathic hypersomnia in adults.

In addition, your health care provider might recommend that you develop a regular nighttime sleep schedule and avoid alcohol and medications that can affect your sleep.