Narcolepsy is a sleep disorder. The principal symptoms are excessive daytime sleepiness (EDS) including sudden, brief (about 15 minutes) sleep attacks, cataplexy (sudden loss of muscle tone), hallucinations, that occur at the onset or offset (when starting to wake up) of sleep, and sleep paralysis.
Narcolepsy is believed to be caused by a deficiency of the brain chemical orexin A and B (also known as hypocretin 1 and 2). 90 % of patients that have narcolepsy with associated cataplexy have little or no orexin in the fluid that surrounds the brain and spinal cord (cerebrospinal fluid). Those who have narcolepsy without cataplexy probably have a different cause, as their orexin levels are normal.
To some extent narcolepsy runs in families, but genetics alone are not usually enough for a patient to develop narcolepsy. Scientists believe that it may be secondary to the body’s own immune system attacking the areas in the brain that produce orexin, but it is unclear why some people develop narcolepsy and others do not
It affects both sexes equally. It usually begins in early adult life and levels off in severity at about 30 years of age.
Excessive daytime sleepiness (EDS)occurs every day, regardless of the amount of sleep obtained at night. EDS is usually experienced as a heightened sensitivity (sometimes an almost irresistible susceptibility) to becoming sleepy or falling asleep, especially in sleep-inducing situations. Patients describe the problem as sleepiness, tiredness, lack of energy, exhaustion, or a combination of these feelings, either continuously or at various times throughout the day.
Sometimes sleepiness occurs so suddenly and with such overwhelming power that it is referred to as a "sleep attack." Some patients have several "attacks" each day. When the attack occurs during the day, sleep usually lasts for less than 30 minutes, but sometimes the patient stays asleep for several hours.
Paradoxically, persons with narcolepsy who suffer from significant daytime sleepiness often describe poor quality, interrupted sleep at night. Many complain of difficulty in memory. Some describe "automatic behavior", such as driving past a highway exit or writing off a page, with no memory of the previous few minutes. Occasionally there will be introductions of blurred vision or diplopia due to their sleepiness. Narcoleptics do not sleep longer than normal during a typical 24-hour period, but their sleep is non-restorative.
Cataplexy is an abrupt loss of voluntary muscle tone, usually triggered by emotional arousal. Attacks can range in severity from a brief sensation of weakness to total collapse lasting several minutes.
Hallucinations are intense and vivid, sometimes accompanied by frightening auditory, visual, and tactile sensations, and occur just on awakening or falling asleep. Occasionally, they are extremely difficult to distinguish from reality.
Sleep paralysis is a complete inability to move for one to two minutes immediately upon awakening. Hallucinations may occur at this time.
Many of the symptoms of narcolepsy such as cataplexy, hallucinations, and sleep paralysis are due to an intrusion of the deep sleep stage REM, while the patient is awake. This causes some of the “symptoms” of sleep (dreams/ hallucinations, paralysis) to occur during the wake stage.
Diagnosis is based on the medical history and physical examination. Sleep studies are necessary to diagnose narcolepsy. On an overnight sleep study, doctors may diagnose narcolepsy by measuring how quickly the patient falls asleep and how often rapid eye movements (REM) are present at or near the onset of sleep. In addition, the patient often requires a sleep study during the day to document how sleepy they are, despite having a full night’s sleep on the previous night.
In the treatment of narcolepsy, it is important to define clear outcome goals for specific target symptoms. There are medications to use to help with narcolepsy and its symptoms, as well as behavioral modifications to help the patient deal with this disease.
Some important behavioral changes are:
- Avoiding drugs that can affect sleep (even over the counter medications).
- Napping during the day, for 20-30 minutes may increase a narcoleptic’s ability to function well and maintain work and social obligations.
- Narcoleptics often have many difficulties socially and in their work related lives, due to their disease. There are some professionally supervised support groups that help patients cope with these issues. More information can be found at http://www.narcolepsynetwork.org/.
Medication treatments are usually divided into two categories that address different treatment goals: daytime sleepiness and cataplexy. The only medication shown to improve both of these problems is sodium oxybate (Xyrem).
A relatively new “wake promoting” agent, called modafinil (Provigil), has recently become the primary treatment in improving daytime sleepiness. Other more traditional stimulants - dextroamphetamine (Dexedrine), methylphenidate (Ritalin), and pemoline (Cylert) - can also be used.
Stimulants are generally given in a single morning dose or in morning and lunchtime doses. Too high a dose or one that is given later in the day may disturb nocturnal sleep. Generally, the biggest therapeutic concern is the development of tolerance - some clinicians believe that the use of drug holidays may reduce this problem. Tolerance has not been noted to be a major problem with modafinil.
The current treatments for the sometimes disabling symptoms of cataplexy are sodium oxybate and different types of anti-depressant drugs, such as venlafaxine (Effexor) and fluoxetine (Prozac). The antidepressants are able to decrease the amount of REM and therefore do not allow its intrusion into the awake state, which is the cause of cataplexy.
More information is available at http://www.ninds.nih.gov/disorders/narcolepsy/narcolepsy.htm .