Symptoms:

• Persistent drowsiness (hypersomnia -- excessive daytime sleepiness)
• Difficulty for a young adult to stay awake during classes or work
• A sudden, uncontrollable need to sleep during the day (sleep attack)
  • May occur several times during a day
  • Usually happens after eating, but may occur at any time
  • Each sleep episode lasts about 15 minutes
• Awake and refreshed feeling after each episode
• Hallucinations, visual (sight) or auditory (hearing) may come before sleep, or occur during the sleep episode
• Sudden loss of muscle tone (cataplexy)
  • May be associated with emotional reactions such as laughter or anger
  • May be similar in appearance to seizures
• Temporary inability to use muscles (sleep paralysis)
  • Occurs immediately upon awakening
  • Occurs at the onset of drowsiness

Signs and tests:

Examination and tests are used to rule out disorders that may cause similar symptoms, including sleepiness that results from seizures, sleep apnea, insomnia, restless leg syndrome, other sleep disorders, or other medical, psychiatric, or neurological (nervous system) diseases.

The diagnosis is confirmed by sleep studies (polysomnogram), particularly a study called the Multiple Sleep Latency Test (MSLT). During MSLT, the time it takes to fall asleep during daytime nap opportunities is measured .

Tests to rule out other disorders may include:

• Lab tests (variable, depending on the suspected cause)
• ECG (measures the heart's electrical activity)
• Monitoring of breathing
• EEG (brain activity measurements)
• Recording of the amount of sleep
• Sleep lab study -- recording of observed sleep cycle, including episodes of REM sleep (the part of the cycle where dreaming occurs)
• Blood tests -- determines the presence of narcolepsy-related genes, or medical illnesses associated with excessive sleepiness

Recently, patients with narcolepsy have been found to have low levels of hypocretin (a protein made by the brain) in their spinal fluid. More research will determine how useful this test is in diagnosing narcolepsy.