Narcolepsy is a disorder that happens when your brain’s control of your sleep-wake cycle is faulty. You can get so drowsy during the day that you might fall asleep suddenly while driving or eating. Some people may have episodes of severe muscle weakness triggered by shock or other strong emotions. Still others may only get mildly sleepy once in a while.
This lifelong condition comes in several distinct types.
Type 1 Narcolepsy
Of the two major forms of the disorder, this is easier to diagnose. Type 1 used to be called narcolepsy with cataplexy. The term refers to sudden, temporary muscle weakness that can leave you immobilized. Anger, excitement, or laughter leads you to lose muscle control. You might fall or slur your speech. These episodes may last a few seconds or a couple of minutes. You’ll be awake and aware of what’s happening.
You may also have other typical symptoms of narcolepsy, such as:
- Extreme sleepiness during the day
- Unstoppable sleep attacks -- a dangerous urge to sleep anywhere, and anytime, such as while walking
- Sleep paralysis, when you’re briefly unable to move
- Vivid and sometimes scary hallucinations
- Interrupted sleep or not being able to fall asleep or stay asleep at night
Type 2 Narcolepsy
This was once called narcolepsy without cataplexy, meaning you don’t lose muscle control. Other than that, your symptoms will be similar to that of type 1 narcolepsy.
This is the rarest type. It can happen after an injury to a deep part of your brain called the hypothalamus that regulates your sleep. Secondary narcolepsy also can be caused by a brain tumor, multiple sclerosis, or brain inflammation called encephalitis. You might have common symptoms of narcolepsy such as fragmented sleep at night. But you also might need to sleep a lot -- more than 10 hours per night.
Experts don’t know exactly how narcolepsy happens. But they believe that it might result from your own immune system attacking the part of your brain that makes hypocretin (orexin), a hormone that regulates sleep. Type 1 narcolepsy is linked to lower levels of this brain chemical. The precise cause of type 2 is unknown.
Your genes also might raise your risk. Researchers found that people with narcolepsy have changes in certain genes, specifically the T-cell receptor gene and a group of genes called the human leukocyte antigen complex. If a family member has narcolepsy, you’re up to 40 times more likely to get it than someone without a family history. Still, narcolepsy is very rare. Any child of yours has only about a 1% chance of inheriting it.