What Are the Types of Narcolepsy? Sleep Experts Explain the Differing Presentations of This Sleep Disorder
Narcolepsy is often portrayed in film and entertainment in ways that make light of this sleep disorder, researchers report. What's more, on-screen images typically fail to depict narcolepsy's various presentations and diversity of symptoms, according to the nonprofit Project Sleep. So let's set the record straight: there are two main types of narcolepsy, but only one is associated with episodes of cataplexy, a sudden loss of voluntary muscle control.
An estimated 200,000 people in the US have narcolepsy, with undiagnosed cases providing the potential for an even higher number, says the National Institute of Neurological Disorders and Stroke (NINDS).
Excessive daytime sleepiness is a core symptom of both types of narcolepsy, says NINDS. Other symptoms may include cataplexy, sleep paralysis, hallucinations, fragmented sleep, and automatic behaviors. Markers of the condition are most likely to first surface in childhood or early adulthood, but a person can develop narcolepsy at any point in their lives.
Here's how sleep specialists explain the types of narcolepsy, how they differ, and common treatments.
What are the different types of narcolepsy?
There are two primary narcolepsy types: type 1 and type 2, plus a third, rare type, which stems from an injury of the brain's hypothalamus region, according to the Division of Sleep Medicine at Harvard Medical School.
Narcolepsy type 1
This is most common and widely known form of the disease. Along with the previously mentioned symptoms, people with this form experience cataplexy.
Athanasios Kaditis, MD, adjunct clinical assistant professor of Child Health at the University of Missouri School of Medicine, says cataplexy is "an abrupt, bilateral, complete or partial loss of muscle tone." Intense positive or negative emotions such as laughter or anger trigger it, with episodes lasting from a few seconds to a few minutes, Dr. Kaditis tells Health.
According to Mayo Clinic, cataplexy episodes may involve physical changes such as head drooping and slurred speech, and the frequency of such events is highly varied. While some people have multiple episodes a day, others will only have one or two each year.
In addition to cataplexy, people with narcolepsy type 1 have low levels of hypocretin-1, the chemical responsible for controlling wakefulness. The exact cause of this is unknown, but researchers theorize it may be an autoimmune response. If this is the case, the immune system would be mistakenly attacking the brain cells which contain this brain hormone, says NINDS.
Cataplexy is a strong indicator of narcolepsy type 1, but 30% of instances are due to other conditions, such as Niemann-Pick Disease Type C and Angelman Syndrome, per a 2019 review in Sleep Medicine.
Sleep specialists will perform an overnight sleep study and next-day nap test to confirm a narcolepsy type 1 diagnosis. A polysomnogram will record points such as eye movement and brain activity. This can also determine if REM (rapid eye movement) sleep occurs earlier than is typical, says NINDS.
The following day, a multiple sleep latency test (MSLT) monitors people as they take naps. It records how long a person takes to fall asleep and when they enter REM sleep, says Alex Dimitriu, MD, double board-certified in psychiatry and sleep medicine and founder of Menlo Park Psychiatry & Sleep Medicine.
Doctors can also use hypocretin-1 levels to help confirm narcolepsy by "measuring levels of hypocretin or orexin in the cerebrospinal fluid. This is often done using a spinal tap," Dr. Dimitriu tells Health. Hypocretin levels of less than 110 picrograms per milliliter "are often diagnostic of" narcolepsy type 1, he adds.
Narcolepsy type 2
Without cataplexy and low hypocretin levels, it can be more challenging to diagnose type 2 narcolepsy. Symptoms tend to be less severe in nature than in people with type 1. On top of that, the main sign, excessive daytime sleepiness, can be caused by a myriad of other sleep conditions (sleep apnea, for one), which are easier to determine.
People with type 2 narcolepsy "may not get a diagnosis for years," Chelsie Rohrschieb, PhD, head neuroscientist and sleep specialist for Wesper, tells Health. "Generally, doctors will first run tests to rule out any underlying health conditions such as anemia, chronic fatigue syndrome, hypothyroid, cancer, and mental illness. Then they will order a sleep study to rule out sleep apnea."
Once doctors rule out other health conditions, a sleep specialist may have you do the overnight sleep study, daytime nap study, or both. Similar to narcolepsy type 1, people with type 2 will also show a shorter time to enter REM sleep and to fall asleep, says Dr. Dimitriu.
Some researchers believe narcolepsy type 2 is a precursor to type 1, adds Dr. Dimitriu.
Per the American Academy of Sleep Medicine, people may be classified as having type 1 if their hypocretin levels are low, even if they don't have cataplexy,
Unlike narcolepsy types 1 or 2, secondary narcolepsy has an exact cause you can point to: an injury of the hypothalamus, the area of the brain regulating sleep. According to Dr. Rohrschieb, hypothalamus injuries can occur due to:
- Head trauma
- A brain tumor
- Multiple sclerosis
- Brain inflammation
In addition to experiencing typical narcolepsy symptoms, people with this condition may require extensive sleep (over 10 hours) and experience severe neurological issues, reports the Division of Sleep Medicine at Harvard Medical School.
In this case, doctors must address both the underlying cause of the brain injury and the narcolepsy itself, says Dr. Rohrschieb. In terms of symptom relief, people with secondary narcolepsy are treated similarly to those with types 1 and 2, adds Dr. Rohrschieb.
How are type 1 and type 2 narcolepsy treated?
While the exact formula is different for everyone, treatment generally includes a mixture of lifestyle changes and medication.
According to NINDS, behavioral treatment includes:
- Regular naps.
- Waking up and going to sleep at consistent times.
- Getting regular exercise.
- Avoiding alcohol and nicotine before bed.
People with narcolespy are strongly encouraged to practice good sleep hygiene and stick to a consistent sleep schedule, adds Dr. Rohrschieb.
As for medication, Mayo Clinic says options include:
- Stimulants, which help people stay awake during the day
- Selective serotonin reuptake inhibitors (SSRIs), which fight off REM sleep
- Tricyclic antidepressants, to treat cataplexy
- Sodium oxybate (Xyrem), a nighttime option for treating cataplexy
After diagnosis, a sleep specialist can determine the right combination of treatment for you to try.
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