You've probably seen it in movies a hundred times?the caricature of narcoleptics: one moment they're chatting with you over dinner; the next, they're fast asleep, their faces in their dinner plates. This caricature, more hyperbolic than true, nevertheless points to a symptom of narcolepsy which makes narcoleptics vulnerable?their involuntary loss of muscle control. The truth is that even during these episodes of involuntary loss, narcoleptics are often fully conscious of their situation. And that is no laughing matter. Often unrecognized and misdiagonosed, this sleep disorder has been the source of trauma in many victims' lives. What, then is narcolepsy and what are the symptoms of this disorder?

Narcolepsy is a sleep disorder characterized by the brain's innability to maintain normal wakefulness during the day. We also know that in narcoleptics, the regular pattern of REM sleep is disturbed. Tested in sleep laboratories, people with narcolepsy enter REM sleep within a few moments of falling asleep while normal sleepers move into REM sleep after 80-100 minutes. This abnormal entrance into REM sleep also seems to be associated with the abnormal daytime appearance of conditions usually experienced during sleep?lack of muscular control, sleep paralysis and hypnagogic dream visons. According to Dr. Jerome Siegel of the Center for Sleep Research, ?a group of neurons that is supposed to be active during REM sleep to suppress muscle tone and protect us from the elaborate motor programs that accompany our dreams is being triggered during waking.?

Researchers have theorized that the symptoms of narcolepsy emerge from this abnormal triggering of aspects of REM sleep during the day. These symptoms include

1) Sleep episodes during the day that last anywhere from 15 minutes to 3 hours or more. Despite the extra sleep, narcoleptics experience persistent drowsiness during the day, which means that, if their condition is not recognized and treated, they can literally be time-bombs on the highway.

2) Catalepsy?the experience of being unable to move for several seconds or more. Catalepsy is probably the most prominent and caricatured symptom of narcolepsy, appearing in 70% of cases. Often, catalepsy takes the form of a seizure, an episode of involuntary loss of muscle control. These attacks can occur at any time during the waking period. Prompted frequently by laughter, intense emotions or even athletic exertion, these episodes can range from being barely perceptible (tremor of the lids) to total physical collapse. The one feature that distinguishes catalepsy from other seizures such as epilepsy is that the patient is almost always fully conscious?even during the most severe episodes.

3) Sleep paralysis'a milder version of catalepsy; sleep paralysis is the inability of the subject to move for a few seconds just before falling asleep or awakening. While most of us remember having such experiences once in a while, they are daily occurrences with narcoleptics.

4) Hypnagogic hallucinations or vivid dreams?which we all have felt or seen just before falling asleep. The difference with narcoleptics is that they live these vivid hallucinations even when awake. Known as hypnagogic dream images when we experience them just before sleep and hypnopompic dream visions when we experience them prior to awakening, these delusional, visual and sometimes auditory images are often vivid and frightening.

5) Automatic behavior?which usually occurs while the subject is asleep. This automatic behavior includes talking, eating, putting things away, brushing hair, changing clothes, actions that are performed while the subject is asleep. However, when awakened, the subject has no memory of performing such activities.

Although research on narcolepsy is growing, not much is known about the causes of the condition. What we do know is that this disorder affects between 1 in 1000 and 1 in 2000 people in the US. Its rates are lowest in Israel and highest in Japan (1 in 600), a situation which suggests that there is a genetic component to the disease. Research suggests as well that narcolepsy may be triggered by an abnormality in an area of chromosome 6, known as the HLA complex which controls sleep patterns. Complicating factors that may precipitate this condition include stress, hormonal changes, trauma, infections and immune system dysfunction. As a matter of fact, a great deal of research is now focused on the possibility that narcolepsy is an auto immune disorder.

Treatment options available now tend to treat the symptoms only, not the cause. They include the use of central nervous system stimulants(like provigil) to sustain wakefulness during the day and depressants at night to suppress REM sleep.

Resources: Siegel Lab at the Center for Sleep Research National Institute of Neurological Disease and Stroke Wikipedia