An in-depth report on the causes, diagnosis, and treatment of narcolepsy.
Narcolepsy is considered a primary hypersomnia condition. The word narcolepsy comes from two Greek words roughly translated as "seized by numbness." The two primary symptoms in narcolepsy reflect this phrase:
Some, but not all, patients experience other symptoms:
Rapid eye movement (REM) sleep is abnormal in narcolepsy. In fact, narcolepsy is sometimes defined as the loss of boundaries between wakefulness, non-REM sleep, and REM sleep. REM sleep is the active, dreaming phase of sleep.
Excessive Sleepiness. All people with narcolepsy experience excessive sleepiness during the day with episodes of falling asleep rapidly and inappropriately, even when fully involved in an activity. It is sometime described as an irresistible daytime need for naps, which will generally refresh the patient. These events may be characterized by the following behaviors:
Cataplexy. Cataplexy is an abrupt loss of muscle tone or strength that results in an inability to move and always occurs during wakefulness. Symptoms of excessive daytime sleepiness are often present for years before symptoms of cataplexy develop. Around two thirds of patients with narcolepsy have symptoms of cataplexy. Cataplexy occurs in about two-thirds of narcolepsy patients. The following events may be triggers:
Muscle reflexes are completely absent during a cataplectic attack. Cataplectic attacks can be very minimal and appear as passing weakness or affecting only the eyelids and face. They may, on the other hand, be so severe that they weaken the whole body. In the most severe form of cataplexy, attacks can recur repeatedly for hours or days. Abrupt withdrawal from certain drugs used to treat narcolepsy, notably clomipramine, can trigger this uncommon but troublesome occurrence.
Cataplexy may have the following characteristics:
Atonia. Atonia is a sense of paralysis that occurs between wakefulness and sleep, usually upon waking or sometimes at the onset of sleep. The person is conscious but cannot speak, move (cannot even open the eyes), or breathe deeply. Atonia rarely lasts beyond 20 minutes, but when it first occurs, this experience can be terrifying, particularly if the patient also develops hallucinations.
Hypnagogic Hallucinations. Hypnagogic hallucinations are dreams that intrude on wakefulness, which can cause visual, auditory, or touchable sensations. They occur between waking and sleeping, usually at the onset of sleep, and can also occur about 30 seconds after a cataplectic attack.
Such symptoms may also appear in other sleep disorders and are probably related to extreme sleepiness. In general, cataplexy must also be present for a clear diagnosis of narcolepsy. Some experts believe, however, that some patients with narcolepsy may experience hypnagogic hallucinations and daytime sleepiness and not cataplexy.
Microsleep and Automatic Behavior. In some cases, patients have so-called microsleep episodes, in which they behave automatically without conscious awareness. Such automatic behavior may not be recognized as part of a disorder by either patients or the people around them. Some examples include:
Disturbed Sleep. Nighttime sleep is often disturbed in narcolepsy, but it is usually mild to moderate and does not account for the daytime sleepiness experienced by people with narcolepsy.
Periodic Limb Movement Disorder. Many patients with narcolepsy experience periodic limb movement disorder, also called PLMD (formerly known as nocturnal myoclonus). In PLMD, the leg muscles involuntarily contract every 20 - 40 seconds during sleep, occasionally arousing the patient. The patient is usually unaware of the cause of the interruption.
Most people need about 8 hours of sleep each day. Individual adults differ in the amount of sleep they need to feel well rested, however. (Infants may sleep as many as 16 hours a day.)
The daily cycle of life, which includes sleeping and waking, is called a circadian (meaning "about a day") rhythm, commonly referred to as the biologic clock. Hundreds of bodily functions follow biologic clocks, but sleeping and waking comprise the most prominent circadian rhythm. The sleeping and waking cycle is about 24 hours. (If confined to windowless apartments, with no clocks or other time cues, sleeping and waking as their bodies dictate, humans typically live on slightly longer than 24-hour cycles.) It usually takes the following daily patterns:
In addition, daily rhythms intermesh with other factors that may interfere or change individual patterns:
The response to light signals in the brain is an important key factor in sleep:
Sleep consists of two distinct states that alternate in cycles and reflect differing levels of brain nerve cell activity.
Non-Rapid Eye Movement Sleep (Non-REM). Non-REM sleep is also termed quiet sleep. Non-REM is further subdivided into three stages of progression:
With each descending stage, awakening becomes more difficult. It is not known what governs NonREM sleep in the brain. A balance between certain hormones, particularly growth and stress hormones, may be important for deep sleep.
Rapid Eye-Movement Sleep (REM). REM sleep is termed active sleep. Most vivid dreams occur in REM sleep. REM-sleep brain activity is comparable to that in waking, but the muscles are totally relaxed, possibly preventing people from acting out their dreams. In fact, except for vital organs like lungs and heart, the only muscles not relaxed during REM are the eye muscles. REM sleep may be critical for learning and for day-to-day mood regulation. When people are sleep-deprived, their brains must work harder than when they are well rested.
The REM/Non-REM Cycle. The cycle between quiet (non-REM) and active (REM) sleep generally follows this pattern:
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