Signs and Symptoms of Narcolepsy
Narcolepsy is technically defined by excessive daytime sleepiness and sleep attacks, in conjunction with one or more auxiliary symptoms, which can include cataplexy, hallucination, and sleep paralysis. The entire tetrad of symptoms, as it is often called, occurs only in about 10 percent of cases. Cataplexy is the most common auxiliary symptom of narcolepsy, afflicting roughly 70 percent of patients. Sleep paralysis and hypnogogic and hypnopompic hallucinations are less common. Sleep paralysis occurs in 30 percent of cases, and hallucination in approximately 25 percent. In narcoleptic patients, these symptoms usually accompany cataplexy; they rarely occur on their own. When they occur as a set, the symptoms are intensified.
Excessive Daytime Sleepiness and "Sleep Attacks"
The most prevalent symptom of narcolepsy is suddenly and unexpectedly falling asleep during the day. In fact, narcoleptic attacks often occur at inappropriate times with significant consequences for those who experience them. For example, patients with narcolepsy may fall asleep while driving, during a meeting, and even during sex.
A typical bout of sleep may last 15 minutes to an hour, rarely longer. Sleep can reoccur within one to several hours. Usually, a patient wakes up refreshed, tires slowly within an hour or two, and then falls asleep again. The cycle then repeats. Some people may not actually fall asleep but struggle with extreme sleepiness throughout the day. Excessive daytime sleepiness has been documented in studies using EEGs that show the occurrence of abnormal daytime biorhythms. Many people with narcolepsy try to combat the overwhelming urge to sleep with stimulants like caffeine or other drugs. Uncontrollable sleepiness, combined with continual efforts to resist it, often leads to significant disruption in the lives of people with narcolepsy. Usually, a day's worth of compounded sleepiness results in deep, brief sleep episodes.
It may seem that narcolepsy patients would have normal nocturnal sleep habits. Ironically, this is not the case. When measured with polysomnography, narcolepsy patients demonstrate nonspecific changes in their sleep pattern, which include an increased number of arousals, sleep maintenance insomnia, and less time spent in stage 1 sleep.
Cataplexy, the most prevalent secondary symptom of narcolepsy, is almost exclusive to narcolepsy. It is the sudden, temporary loss of muscle tone in the body. When loss of muscle strength is severe, all the voluntary muscles in the body are affected, leading to complete collapse. In mild cases, the loss in muscle strength can be quite subtle, partially involving only a few muscle groups. For example, partial neck muscle weakness may cause a person to struggle to keep their head from drooping.
Interestingly, the muscles of the eyes are not affected during cataplexy; individuals can move their eyes during a cataplectic episode. The effects of cataplexy are all-consuming, which makes it nearly impossible for a bystander to guide an individual out of an episode. Furthermore, loss of muscle function may not be evident, and the patient may experience only a vague feeling of weakness. Cataplectic episodes usually last from a few seconds to 30 minutes; rarely does an attack last longer.
Cataplexy is thought to occur during times of intense emotional states. For example, the shock of winning the lottery or extreme anger may trigger an episode. This distinguishes cataplexy from its host condition, narcolepsy, whose onset does not discriminate with regard to the patient's emotional state.
During a cataplectic attack, the person is completely awake and later will have total recall of the entire event. If episodes last longer than a few minutes, the patient may begin to hallucinate (distinguishable in occurrence from those described below). It is extremely rare for cataplexy to occur independently of narcolepsy. Indeed, excessive daytime sleepiness and cataplexy are sufficient for a diagnosis of narcolepsy.
Hypnogogic and Hypnopompic Hallucinations
Hypnogogic and hypnopompic hallucinations are not peculiar to narcolepsy, though they occur at a very high rate of frequency in most cases of narcolepsy. However, they are the predominant subsymptom in only an estimated 5 percent of narcolepsy patients and appear in other disorders as well. Hypnogogic hallucinations occur while falling asleep, and hypnopompic hallucinations upon awakening. Both last a few minutes. The hallucinations can be visual, auditory, or tactile and often frighten or disconcert the patient with terrifying shapes and noises. It is possible to wake up a patient during hypnogogic and hypnopompic hallucinations without further distressing them.
These hallucinations are similar to nightmares, in that they are typically more intense, and their effects last longer than mild dreams or daydreams. In the past, patients who suffered from hallucinations were sometimes misdiagnosed as schizophrenic.
Sleep paralysis, the inability to move immediately before falling asleep or upon awakening, has been described and documented since the early 19th century. People who experience sleep paralysis have described feeling afraid, as if some person or creature were sitting on their chest, holding them down.
Like hypnogogic and hypnopompic hallucinations, sleep paralysis is a nonexclusive secondary symptom of narcolepsy. Sleep paralysis usually lasts from a few seconds to 30 minutes and is usually accompanied by hypnogogic and hypnopompic hallucinations. Like hallucinations, sleep paralysis can be alleviated temporarily if an observer intervenes and wakes up the patient.