How Narcolepsy Blurs the Line Between Awake and Asleep

It’s all in the brain chemistry.

By Jacqueline Ronson on May 29, 2017 | Inverse.com

Narcolepsy is a sleep disorder that can cause a variety of strange and often terrifying symptoms, including sleep attacks and temporary paralysis. It’s a neurological disorder that has to do with how our bodies regulate the boundary between being awake and being asleep, and while not every narcoleptic person has the same symptoms, scientists have a pretty good idea of how the disease works. Unfortunately, they’re still figuring out how to fix it.

In 1999 researchers at the Stanford University School of Medicine identified hypocretin, a substance that allows for the transmission of chemical messages in the brain, as a key player in narcolepsy. They found that dogs with narcolepsy had a specific mutation affecting the hypocretin receptor gene, which regulates the hypocretin neurotransmitter.

Hypocretin has since been found to play a key role in human narcolepsy as well. The chemical essentially works to tell the brain to stay awake — the last time you fought to stay awake while driving or watching a movie, it’s likely you had hypocretin on your side.

Hypocretin is only transmitted in a small bundle of neurons, located in the brain’s hypothalamus. These neurons can become damaged, which stops the flow of hypocretin and leads to narcolepsy. Doctors suspect that genetics, autoimmune disorders, and other neural trauma can lead to the degradation of these important pathways.

There are four classic symptoms of narcolepsy, though it’s rare for one patient to display all of them. Narcoleptics frequently complain of daytime sleepiness — they feel excessively tired during the day, regardless of how much they slept. They can be overcome with drowsiness in sudden sleep attacks. Falling asleep standing up is not common; it’s more like the sort of deep tired where you just can no longer keep your eyes open, until you ultimately give in.

The stereotype of narcoleptics suddenly passing out probably comes more so from a separate symptom, called cataplexy, which is a sudden onset of muscle weakness. It can affect just a small part of the body, like the face, or it can overcome a whole person, causing them to collapse. It is sometimes brought on by strong emotions, including laughter and rage. Someone in the midst of cataplexy may appear passed out, but they are in fact conscious. It is as if their body is asleep but their brain is awake.

Some sufferers also experience hypnagogic hallucinations, which feel like a very intense, vivid dream but take place in the space between wakefulness and sleep, often occurring just before falling asleep. This can occur in conjunction with the fourth symptom, sleep paralysis, which can make it particularly frightening. The body cannot move, as if it is sleeping, and the mind is full of very real feeling, dreamlike hallucinations, although it is awake.

People with narcolepsy have disturbed sleep, too. They often fall very quickly asleep and enter the rapid eye movement (REM) phase nearly immediately. This has one benefit — they will feel rested after just a short amount of sleep. But nighttimes can be difficult, as the boundary between awake and asleep remains porous, and sleep is constantly interrupted.

There is no cure for narcolepsy, and sufferers are often prescribed a slew of medications to help them stay awake during the day, and asleep at night. A better understanding of how hypocretin is regulated by the brain could one day lead to better treatments that reverse the problem at its source, rather than just managing symptoms.