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Diagnosis and Management of Narcolepsy
by Michael R. Slattery, M.D., Division of Neurology/Sleep Medicine
Narcolepsy is a condition that causes excessive daytime sleepiness in the form of "sleep attacks" or bouts of uncontrollable sleepiness. Within the sleep disorder literature, narcolepsy falls under the category of the Disorders of Excessive Somnolence "DOES"), as opposed to the insomnias, which are referred to as Disorders of Initiating and Maintaining Sleep ("DIMS").
The age of onset of narcolepsy is generally in adolescence or early adulthood. At least .6 % of the population is estimated to have a narcoleptic condition. This disorder is relatively as common as other neurologic conditions, such as Multiple Sclerosis and Parkinson's disease. An increased incidence of narcolepsy also appears to run within some families.
Sleep History and Symptoms
A thorough sleep history can determine whether a patient's sleepiness is normal. The DOES patient will generally be able to fall asleep easily when left alone, and the patient history will likely show a pattern of repeated instances of sleep in inappropriate situations, such as while driving, eating, or during conversation.
In addition to excessive daytime sleepiness, patients with narcolepsy often have other associated symptoms, including the three described below:
Cataplexy. Cataplexy involves sudden attacks of muscle weakness, usually associated with strong emotions such as laughter, anger or fear. These attacks usually last less than one minute.
Sleep Paralysis. Patients with sleep paralysis experience episodes of total body paralysis, either upon awakening or as they are falling asleep.
Hypnagogic Hallucinations. Hypnagogic hallucinations involve the perception of hearing or seeing things when these patients are falling off to sleep. The sensation is as if one is going directly into a dream.
These associated symptoms of cataplexy, sleep paralysis, and hypnagogic hallucinations are thought to be related to abnormal intrusions of Dream State or REM sleep. Only 20-30% of patients with narcolepsy will develop this full array of symptomatology. Associated Difficulties
Patients with narcolepsy experience significant difficulties due to their sleepiness. Issues may include impaired driving ability and motor vehicle accidents. Cataplectic spells, with their associated extreme muscle weakness, can also occur when driving and severely impair driving ability. Patients with narcolepsy also develop decreased work productivity and occupational problems, as well as interpersonal problems, related again to their excessive sleepiness.
Diagnosis
Narcolepsy is diagnosed with sleep studies, including an overnight polysomnogram followed by a multiple sleep latency test, (MSLT). The polysomnogram records the patient's night time brain waves, muscle activity, limb movements, heartbeat, and breathing. In the course of the overnight polysomnogram other sleep disorders such as obstructive sleep apnea or periodic leg movements of sleep are assessed as well. These conditions can also cause excessive daytime sleepiness and are included in the differential diagnosis. On the day following the polysomnogram, the MSLT is conducted. The patient is asked to take multiple naps, and sleep patterns are examined using standard somnographic techniques. The MSLT allows the clinician an opportunity to gather evidence of excessive sleepiness as well as indications of the premature onset of REM or the dreaming state of sleep.
Treatment
If narcolepsy is diagnosed, wake-promoting medications can be prescribed to treat the excessive sleepiness. These medications include Cylert, Ritalin, and a new agent, Provigil. If cataplexy or sleep paralysis is present, effective medication therapy for these problems is also available, usually starting with anti-depressant medications in the tricyclic anti-depressant class.
Narcolepsy is a serious condition which can have a dramatic impact upon an individual's personal and professional life. If bouts of sleepiness or cataplexy are uncontrolled, this condition may also be life-threatening. With the proper diagnosis and treatment, narcolepsy can be monitored and controlled over time, allowing patients to develop strategies of long-term management for this condition.
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