Narcolepsy Overview
Narcolepsy is typically characterized by the following four symptoms with varying frequencies:
- Excessive daytime sleepiness (90%)
- Cataplexy (sudden and temporary loss of muscle tone often triggered by emotions such as laughter) (75%)
- Hallucinations (vivid dreamlike experiences that occur while falling asleep or upon awakening) (30%)
- Sleep paralysis (paralysis that occurs most often upon falling asleep or waking up; the person is unable to move for a few minutes) (25%)
- Frequently, narcolepsy is unrecognized for many years. There could
be a delay of 10 years between the onset of the condition and the
diagnosis.
- Approximately 50% of adults with narcolepsy retrospectively report
symptoms beginning in their teenage years. For most patients, narcolepsy
begins between the ages of 15 and 30 years. It less frequently occurs
in children younger than age 10 years
of age (6%).
- Narcolepsy may lead to impairment of social and academic performance in otherwise intellectually normal children.
- Narcolepsy is a treatable condition. A multi-modal approach is most effective (medications, a regular nighttime sleep schedule, and scheduled naps during the day) is required for the most favorable outcome.
Narcolepsy Causes
Genetic predisposition
Understanding of narcolepsy stems primarily from research involving narcoleptic dogs (for example, special laboratory-bred Dobermans and Labradors). In these animal models, the disorder is transmitted in an autosomal recessive fashion and is characterized mainly by cataplexy. Only 1% of human cases are inherited and, unlike the canine form, are transmitted in an autosomal dominant manner.
Neurotransmitter
The neurotransmitter hypocretin was identified in the last few years and is strongly associated with narcolepsy in dogs with a genetic predisposition. Hypocretin levels in human subjects with narcolepsy have been found to be undetectable or low in several recent studies of patients with narcolepsy. Hypocretin appears to modulate activity in the hypothalamus (the part of the brain associated with sleep). The deficiency of hypocretin might produce sleep attacks. The drug modafinil (Provigil) is useful in the treatment of narcolepsy is believed to activate hypocretin-containing nerve cells.
Exams and Tests
Questionnaires are used to measure excessive sleepiness. The most commonly used questionnaire is the 8-question Epworth Sleepiness Scale (1991).
- Response to each question on a scale from 0 (not at all likely to fall asleep) to 3 (very likely to fall asleep) is obtained.
- The resulting total score is between 0 and 24.
- Although what score constitutes abnormal sleepiness is controversial, total scores above 10 generally warrant investigation.
- You can take the Epworth Sleepiness Scale Test.
For this exam, one needs to come to a sleep laboratory about two hours prior to bedtime without making any changes in the daily habits. Then, the whole night's sleep is monitored and recorded. The following parameters are monitored:
- Electrical activity of the brain (electroencephalogram)
- Electrical activity of the heart (electrocardiogram)
- Movements of the muscles (electromyogram)
- Eye movements (electrooculogram)
- Respirations (oral thermistor or nasal pressure transducer)
If a person has narcolepsy, the polysomnograph shows short sleep latency of usually less than five minutes and an abnormally short latency prior to the first sleep onset REM sleep (SOREMPs). More than two SOREMPs and a mean sleep latency of less than five minutes strongly suggest narcolepsy.
Multiple Sleep Latency Test
In this test, the time taken by a person to fall asleep (sleep latency) during the day while lying in a quiet room is measured. This test is performed the morning after the overnight polysomnogram. The person takes four or five scheduled naps every two hours. The first nap starts two hours after awakening that morning. People with normal sleep and alertness take about 10-20 minutes to fall asleep. Persons with narcolepsy (and other causes of abnormal sleepiness) take a much shorter time (less than five minutes) to go from wakefulness into sleep.
Two weeks prior to these tests, the patient is asked to keep a sleep diary that records bedtime, wake-up times, and nap times. Their physician will inform them to gradually eliminate medications that could affect the sleep tests.
CSF (cerebrospinal fluid) hypocretin test
This has not yet become part of the routine diagnostic tools for narcolepsy, but is being used more frequently. For this test a sample of cerebrospinal fluid is removed by lumbar puncture and sent to the laboratory for analysis. The specificity and sensitivity of the CSF hypocretin test are high enough that it should have clinical usefulness for diagnosis. Thus, defining the precise criteria for the diagnosis of narcolepsy and other sleep disorders is an evolving process.
Narcolepsy Treatment
Self-Care at Home
- Sleep hygiene is very important. For example, many people have an
improvement in their symptoms if they maintain a regular sleep schedule,
usually
seven to eight hours of sleep per night.
- Scheduled naps during the day also help. One study suggested that
the optimal sleep pattern is a combination of scheduled nighttime sleep
(such as from 11:00 pm to 7:30 am) and two 15-minute naps.
- Patient's with narcolepsy should also avoid heavy meals and alcohol (as it can interfere with sleep).
- Driving should be restricted when the patient feels sleepy.
- Children should be encouraged to participate in after-school
activities and sports. A well-designed exercise program can be
beneficial and stimulating.
- Parents should request school personnel to excuse the child from activities if he or she appears drowsy.
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