What is Narcolepsy, You Ask?
Delving Into The Neurological Disorder That Has Taught Us Much About How Sleep Works

Written by Andrew Hines and Kevin Morton

Narcolepsy is a chronic neurological disorder characterized by relentless tiredness, excessibe daytime sleepiness, and pathological manifestations of REM sleep caused by an inability of the brain to regulate sleep-wake cycles normally.

In individuals with narcolepsy, strong emotion during wakefulness can trigger manifestations of REM sleep called cataplexy. While there are four main symptoms of narcolepsy, cataplexy is the hallmark symptom that distinguishes it quite remarkably from any other disorder.

Cataplectic attacks blur the line between sleep and wakefulness. The individual suffering one is awake in most senses of the word--they can hear, see, think consciously, etc.--but elements of REM sleep, namely the paralyzing force of REM atonia, intrude and overlap with the waking state.

The severity of cataplexy varies profoundly among individuals with narcolepsy. Some may experience light weakening of the knees, face, or neck muscles, while more severe cases can bring on near-total muscle paralysis, causing complete falls to the ground. The video below shows what more severe cataplectic attacks look like, first in a man and then in a number of dogs from the decades of narcolepsy research they were involved in at Stanford University.

NARCOLEPSY SYMPTOMS

Excessive Daytime Sleepiness (EDS) is the feeling of persistent fatigue, mental cloudiness, and lack of energy, that may contribute to feelings of depression and an inability to maintain concentration. Many people with narcolepsy find that remaining awake during sedentary activities requires constant effort.

Cataplexy is the sudden loss of muscle tone due to elements of REM sleep overlying wakefulness. Cataplectic attacks are often brought about by strong emotions. A funny joke, for instance, might cause weakness of the knees, or complete (but temporary) paralysis, wherein the person remains conscious. Attacks can occur anytime during the waking period. For those just developing narcolepsy, cataplexy may not show itself until after several weeks or months of EDS.

Sleep Paralysis is the temporary inability to move and speak while falling asleep or waking up, caused by an overlap of REM atonia with wakefulness. Everyone normally experiences this paralysis during REM sleep, our body's way of preventing us from acting out our dreams. But because of a tendency to go directly into REM sleep (known as sleep-onset REM periods (SOREMPs)), people with narcolepsy may frequently experience sleep paralysis as they're trying to fall asleep. Sleep paralysis is also experienced commonly in individuals without narcolepsy, but the frequency in which it occurs for people with narcolepsy makes it an important symptom. (Learn more)

Sleep-Related Hallucinations are images and sounds that accompany sleep onset (hypnogogic hallucinations) or waking up (hypnopompic hallucinations). They commonly accompany sleep paralysis, but aren't experienced by everyone with narcolepsy. These experiences are vivid episodes that may be thought of as REM dreams projected onto the physical world. The hallucinations can sometimes be so strong that this symptom can be mistaken for schizophrenia.

Prevalence: Close to 250,000 Americans are affected by narcolepsy, with fewer than 50,000 diagnosed. 20 to 25% of people diagnosed experience all 4 symptoms of narcolepsy. Similar figures state that around 1 in 2,000 persons have narcolepsy.

Causes Of Narcolepsy

Narcolepsy is believed to be a type of autoimmune disease. An autoimmune disease involves the immune system making a mistake and attacking the body's own cells and tissues. In the case of narcolepsy, it is thought that the immune system attacks cells in the brain that produce a protein called hypocretin, an important chemical for regulating neuron activity and sleep.

Narcolepsy in humans is genetically complex. Across cultures, everyone with narcolepsy has a certain gene called the hypocretin receptor 2. But not everyone with this gene has narcolepsy--it's prevalent in about 25% of people.

Furthermore, despite the importance of this gene, narcolepsy is not very genetic at all. There is only about a 17-25% monozygotic twin concordance, which means that out of all people with narcolepsy who have an identical twin (and thus, someone with an identical genome), only a small percentage of the twins have narcolepsy too.

The ability for narcolepsy to be passed down from parents to children is rather weak as well. There is a small increased familial risk, but it's only about 1-4%.

So while the causes of narcolepsy are not 100 percent elucidated, Dr. Mignot and his colleagues have brought us close. HLA (human leukocyte antigen) molecules have shown us that narcolepsy is very likely an autoimmune disease that produces an abnormality in hypocretin transmitters, and thus a lack of hypocretin. There are still many questions to uncover, but the momentum of our answers is moving us quickly ahead.

For more on the causes of narcolepsy and the research that helped uncover them, check out this 1999 article on Dr. Dement's old site announcing the discovery of the hypocretin receptor 2 gene.

Treatment For Narcolepsy

In searching for a treatment for narcolepsy we first must think of what we are trying to change--a lack of hypocretin. Experiments with mice have shown that we can actually treat narcolepsy by just giving them more hypocretin. The problem is the hypocretin must be injected directly in the brain. We can do this for mice, but for humans we cannot cross the blood-brain barrier (BBB) to carry this out. Thus, the biggest push in narcolepsy treatment now is to develop a drug that can cross that barrier to replace the lost hypocretin.

Another treatment approach of the future would be to address the autoimmune element of narcolepsy before the disorder even develops, by way of correcting the immune system so it does not destroy the hypocretin-destroying cells.

While these are promising directions that the future of narcolepsy treatment holds, treatment available right now does not address the cause as those solutions do, but instead serve to ameliorate the symptoms.

Narcolepsy Medication

The medication for narcolepsy right now currently consists of two main elements:

• Amphetamines to help give the patient as much alertness as possible throughout the day. These pills can help, but are only like a band-aid to help with day-to-day functioning.
• Anti-depressants to help suppress REM sleep and thus decrease the frequency and severity of cataplexy.

Sometimes medication to help the patient sleep consistently throughout the night is also given.

With the right attention and a strong doctor, the right combination of medicines can often get patients back up to around 80% of their normal functionality. But the key in the process is getting diagnosed, which is critically still missing from many people's paths to effective treatment.

Narcolepsy Diagnosis

The medical field and general public as a whole have historically been very unaware of narcolepsy (in addition to many other sleep disorders), and the result has been an extreme lack of diagnosis, or diagnoses late into life after many years of unregulated symptoms and unknown causes. Despite the extraordinary uniqueness of the symptoms of narcolepsy, many do not recognize the symptoms for what they are because they haven't ever heard of narcolepsy. This visitor-submitted story from Shanna in Missouri is a powerful example of this lack of knowledge in the medical field and the consequences it has brought.

Things are starting to gradually change. As awareness slowly increases more and more pediatricians are beginning to recognize the symptoms of narcolepsy early on in their development (often while the patient is in adolescence, in particular between the ages of 10 and 15), referring the children to specialists who can take steps to restore normalcy before much disruption of the patient's life has occurred.

The key is getting diagnosed, and the key to more diagnoses is raising awareness of the disorder. That's precisely what this website is dedicated towards doing, and I invite you to please let us know if you have any ideas on how to further do that.

How Narcolepsy Is Diagnosed

Once it has been brought to the attention of someone who knows what they are doing, narcolepsy is one of the easiest conditions in the world to diagnose. Many of the symptoms--especially sleep-onset REM periods and cataplexy--are among the most blatantly obvious criterion for diagnosis in all of medicine.

Professional diagnoses for narcolepsy use the Multiple Sleep Latency Test (MSLT), which involves a series of short naps throughout the day monitered by a Polysomnogram (PSG). The PSG records brain waves, eye movements, and muscle tone, which can be used to determine when the sleeper is in REM sleep.

The MSLT measures the tendency of a person to fall asleep, and whether REM sleep intrudes abnormally upon sleep onset. During the test, a patient is instructed to fall asleep 4-5 times at intervals of 2 hours over the course of a day. The time it takes the patient to fall asleep is then measured: scores of sleep latency less than 5 minutes indicates hints strongly at excessive daytime sleepiness. This in combination with the presence of sleep-onset REM periods and reports of cataplexy are used to make a definitive diagnosis. Observing two or more SOREMPs within this time period is common.

Narcolepsy Research

Dr. Dement holding one of his narcoleptic dogs as it has an episode of cataplexy. This picture took a really looong time to get right.

For an in-depth interview with the world's leading narcolepsy researcher please visit: Chasing The 'Narcolepsy Gene': An Interview With Dr. Emmanuel Mignot

Narcolepsy is still a relatively newly discovered disorder (the gene causing it was discovered in 1999), but research in the field of sleep medicine is fast growing.

Currently, the Stanford Sleep Clinic (standing on the shoulders of some of the stars of sleep medicine, Drs. William C. Dement, Christian Guilleminault, and Emmanuel Mignot) is at the forefront of narcolepsy research.

In addition, the National Center on Sleep Disorders Research (NCSDR), the National Institute of Neurological Disorders and stroke (NINDS), and other elements of the National Institutes of Health (NIH) conduct important research into the biology of sleep.

If you, or anyone you know, are suffering from the symptoms of narcolepsy that have been described above, it is imperative that you visit a sleep clinic. With the help of patients and the continued striving of researchers and medical personnel, we will continue to move forward towards a cure for narcolepsy that will have a lasting and significant effect.