Narcolepsy

Key Features

• A disorder of excessive sleepiness, manifesting in "sleep attacks"

• Disorder begins in early adult life

• Affects both sexes equally

• Severity levels off at ~30 years of age

Clinical Findings

• Tetrad of symptoms

  • Sudden, brief (~15 min) sleep attacks during any type of activity

  • Cataplexy, a loss of specific or generalized muscle tone

  • Sleep paralysis: a flaccidity of muscles with full consciousness while falling or waking from sleep

  • Visual or auditory hypnagogic hallucinations, preceding sleep or occurring during a sleep attack

Diagnosis

• Sleep study

  • Attacks are characterized by abrupt transition into REM sleep, a necessary criterion for diagnosis

Treatment

• Dextroamphetamine sulfate, 10 mg orally each morning, with increased dosage as necessary

• Modafinil, 200–400 mg orally each morning or armodafinil, 150–250 mg orally each morning

  • Mechanism of action is unknown, but risk of abuse is thought to be lower than with stimulants

  • Modafinil may reduce the efficacy of cyclosporine, oral contraceptives, and other medications by inducing their hepatic metabolism

  • Common side effects include headache and anxiety

• Imipramine, 75–100 mg orally once daily, is effective in treatment of cataplexy but not narcolepsy