Summary of Narcolepsy
Transcript for Narcolepsy
At one time or another you’ve probably had to force yourself to stay awake, maybe while driving or when you’re in a looooong lecture.
In these situations you were exerting control over your sleep-wake cycles.
Narcolepsy is a disorder in which individuals lose the ability to regulate these sleep-wake cycles, so the normal boundary between sleeping and being awake is blurred, leading to characteristics of sleeping occurring while a person is actually awake.
In the brain, there are a special group of neurons that help increase the state of wakefulness, and they extend from the lateral hypothalamus to various parts of the brain like the reticular activating system (or RAS).
In individuals with narcolepsy, there are fewer of these excitatory neurons, and each neuron carries less of the neuropeptides orexin A and B (also called hypocretin 1 and hypocretin 2).
These orexins increasing the activity of wake-promoting regions of the brain, thereby tipping the scales in favor of wakefulness and preventing inappropriate transitions into a sleeping state.
With narcolepsy, it’s thought that an autoimmune process might damage the neurons delivering orexin or that there may be some other direct injury to those neurons.
Either way, when that happens, less orexin is sent out and sleep-related symptoms begin to intrude into wakefulness.
The onset of narcolepsy often happens during adolescence and young adulthood, and is classically associated with four key symptoms.
The first is daytime sleepiness, where people feel chronically sleepy.
They can get sleep attacks where they doze off with little warning, sometimes inappropriately, but they generally don’t sleep more than healthy people in a given 24-hour period.
Most individuals with narcolepsy find that a short, 15-minute nap substantially improves their alertness for a few hours, which suggests that the sleepiness of narcolepsy is caused by a problem with the brain circuits that normally promote full alertness, rather than poor quality or insufficient hours of sleep.
Normally when a healthy person goes to bed, they go through a sleep cycle lasting an hour or more before they reach REM sleep, the stage of sleep characterized by dreaming.
People with narcolepsy fall asleep very quickly, in as little as five minutes, and they often go directly into REM sleep.
This results in their having very vivid dreams, even when they fall asleep for brief periods of time.
The second symptom that often develops over time is cataplexy, which is when some strong emotion (which can be a positive one like laughter, or a negative one like anger) triggers a transient muscle weakness.
That muscle weakness is often partial, affecting the face, neck, and knees, but severe episodes can cause total body weakness or paralysis, causing the person to collapse.