Narcolepsy is a condition characterized by excessive daytime sleepiness often to the point of an irresistible desire to sleep. Many, though certainly not all patients with narcolepsy have sudden attacks of falling asleep triggered by strong emotion or laughter. More commonly patients complain of excessive daytime sleepiness along with difficulty sleeping at night.
In order to better understand narcolepsy, one needs a little background in the normal stages of sleep. There are basically two types of sleep: REM (rapid eye movement) and non-REM. There are four stages of the non-REM sleep, aptly named stages 1 through 4, each somewhat deeper the preceding stage. Ordinarily, when a person goes to sleep, he/she enters stage 1, which is a very light sleep of relatively short duration. After 10-12 minutes, the person enters stage 2 and stays there for another 30-75 minutes. The person then descends into deep sleep or slow wave sleep (stages 3 and 4), from which it is very difficult to be awaken. After about 90 minutes, and not sooner, a person usually enters stage REM (rapid eye movement). REM sleep is the stage during which a person dreams, so named because during these dreams the eyes move rapidly back and forth as if the patient were looking for something. The mind is very active, almost identical to being awake, as demonstrated on brain wave monitors, or EEG. Though the brain is very active, all of the muscles of the body, except for the diaphragm, the muscle of breathing, and the eye muscles, are paralyzed. The person is completely motionless, but the mind is active.
How does all f this relate to narcolepsy?
Narcolepsy is actually a sudden attack of REM sleep in the middle of the day, in the middle of wakefulness. The patient feels the sudden desire to sleep and enters REM sleep with little if any warning. The classic presentation of narcolepsy is:
excessive sleepiness - this can vary from some simple fleeting sleepiness, to overwhelming irresistible sleep.
cataplexy - bilateral muscle weakness, from a few seconds to several minutes.
sleep paralysis - a sensation of being awake, but being unable to move.
hypnagogic hallucinations - terrifying visual hallucinations usually at the onset of sleep associated with being unable to move.
Interestingly, the majority of patients present only with excessive sleepiness, along with insomnia and much disrupted sleep at night. The usual age of onset is the teens and 20s. but it can present even later. Often the person has a lifetime of social problems related to sleepiness and loss of attention, because of frequent small micro-sleep attacks. These patients are, as expected, also at risk of accidents. The incidence of narcolepsy is 0.07-0.2% in the U.S. Narcolepsy is a genetic disease. Narcolepsy is associated with HLA DR2 and DQ1 genes. Narcolepsy with cataplexy in first degree relatives is 20-40 times more frequent that in the general population, but only 1-2% of first degree relatives with narcolepsy have narcolepsy cataplexy.
How is the diagnosis of narcolepsy made?
the test for narcolepsy is the multiple sleep latency test or the MLST. It is a sleep study that takes about a day to perform in the sleep laboratory. The patient is offered five 20 minute opportunities to fall asleep every 2 hours. Patients with narcolepsy generally will fall sleep and rapidly enter REM sleep at least 2 out of the 5 times on the MSLT.
There is treatment for narcolepsy. Patients with narcolepsy have to maintain good sleep hygiene, with planned naps to also coincide with times of maximal sleepiness. They need to avoid staying up too late and to avoid becoming sleep deprived. Medication for narcolepsy addresses the hypersomnolence and the cataplexy. Hypersomnolence s treated with stimulants, chemically related to amphetamine. These include Dexedrine and Methylphenidate given small doses throughout the day to coincide with times of maximal sleepiness. A newer and safer one now available is Modafiniail, taken usually once or twice a day at a dose of 200-400 mg per day. Drugs for cataplexy include tricyclic antidepressant medications, such as Imipramine, as well as some of the newer serotonin reuptake inhibitors, such as Fluoxetine. Because patients with narcolepsy have trouble staying asleep, often complaining of frequent awakening, they sometimes actually need medication to help them fall asleep and stay asleep, such as Zaleplon or Zolpidem.
The most important rule for patients with narcolepsy is to maintain a regular schedule of sleep and to take their medication on a regular basis.
