Narcolepsy is a neurological disorder that affects wake-sleep cycles. It causes fragmented night sleep and extreme daytime sleepiness.
It causes abnormal rapid eye movement (REM) sleep and it can involve cataplexy (brief attacks of muscle weakness and tone that can lead to body collapse).
Narcolepsy can range from mild to severe. In severe cases, it can negatively affect social activities, school, work, and overall health. A person with narcolepsy may fall asleep unexpectedly at anytime and anywhere.
Symptoms tend to appear in the teenage years, or early twenties and thirties. Men and women are equally prone to this disorder. Narcolepsy is the second leading cause of excessive daytime sleepiness after obstructive sleep apnea.
What is narcolepsy?
Narcolepsy is a considered a hypersomnia, or a sleep disorder characterized by excessive daytime sleepiness.
In a typical sleep cycle, a person enters the early stage of sleep, followed by deeper sleep stages for 90 minutes where finally REM sleep occurs.
For people with narcolepsy, REM sleep occurs within 15 minutes in the sleep cycle, and occasionally during the waking hours. Dreams and muscle paralysis occur in REM sleep.
There are three types of narcolepsy:
- Type 1: Narcolepsy with cataplexy
- Type 2: Narcolepsy without cataplexy, which mainly involves excessive daytime sleepiness
- Secondary narcolepsy: This is caused by an injury to the hypothalamus, a part of the brain involved in sleep.
Causes of Narcolepsy
Narcolepsy may be an inherited autoimmune disease that leads to a deficiency in hypocretin, or orexin, a chemical the brain needs to stay awake. Narcolepsy may run in families.
Hypocretin is a neurotransmitter that controls whether we are asleep or awake by acting on different groups of nerve cells, or neurons in the brain. It is produced in the hypothalamus region of the brain.
Most people with type 1 narcolepsy have low levels of this hormone, but those with type 2 do not.
Hypocretin is needed to help us stay awake. When it is not available, the brain allows REM sleep phenomena to interfere in normal waking periods. As a result, people with narcolepsy experience both excessive daytime sleepiness and nighttime sleeping problems.
In an autoimmune disorder, the body’s immune system mistakenly attacks itself and fights off healthy cells as if they were foreign invaders. Other autoimmune diseases include rheumatoid arthritis, celiac disease, and type 1 diabetes.
Symptoms of Narcolepsy
The main symptom of narcolepsy is excessive daytime sleepiness (EDS). Additional symptoms may include cataplexy, hypnagogic hallucinations, and sleep paralysis.
Excessive daytime sleepiness (EDS) is a dogged feeling of sleepiness with a tendency to doze off at intervals during the day, often at unsuitable times. These are known as sleep attacks. It can lead to decreased energy, brain fog, poor concentration, memory lapses, exhaustion, and a depressed mood.
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Hypnogogic hallucinations are vivid, often frightening sensory hallucinations that occur while falling asleep. These could be caused by the blend of wakefulness and the dreaming that occurs with REM sleep.
Cataplexy: This is a sudden muscle weakness in the neck, face, and knees. Some people have only mild weakness, such as head or jaw drop, but some people completely collapse to the ground. These episodes are often triggered by strong emotions, such as shock, surprise, laughter, or anger. The weakness is temporary, lasting 2 minutes or less.
Sleep paralysis: is a brief inability to move or speak while falling asleep or waking up. These episodes can last from a few seconds to several minutes. After the episode ends, people rapidly recover their full capacity to move and speak.
Automatic behaviors can also occur. A person may fall asleep momentarily but continue doing the previous activity, such as driving, without being conscious.
Keeping a sleep journal may help you and the doctor with diagnosis. Chronic daytime sleepiness can stem from a number of conditions. Anyone experiencing excessive sleepiness should seek a medical evaluation to determine the exact cause.
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Narcolepsy is often misdiagnosed at first. It may be confused with a psychological condition, sleep apnea, restless legs syndrome, or another condition.
To determine if a person has narcolepsy, a thorough medical and sleep history, physical exam, and sleep studies, such as a polysomnography and multiple sleep latency test, need to be done.
Sleep studies can help confirm a diagnosis of narcolepsy. The polysomnography is done with an overnight in a sleep clinic. The multiple sleep latency test is done a few hours after the polysomnography.
There is no cure for narcolepsy, but medication can help manage the symptoms. Stimulants can treat sleepiness. Antidepressants can treat symptoms of cataplexy and abnormal REM sleep.
EDS is treated with amphetamine-like stimulants, such as dexamphetamine, methylphenidate, or modafinil. These drugs are first-line therapy because of their low cost, availability, and higher efficacy.
However, they are controlled substances. Except for Modafinil, they can lead to tolerance and abuse.
Side effects include irritability, insomnia and anxiety. Modafinil may cause headache and nausea.
Cataplexy can be lessened by antidepressant drugs, which suppress REM sleep. Treatment may require adjusting as symptoms change.
Clomipramine is used to treat narcolepsy. Selective serotonin reuptake inhibitors (SSRIs) and selective norepinephrine reuptake inhibitors (SNRIs) may also be effective. Side effects may include dry mouth, constipation, and blurred vision.
Sodium oxybate can relieve EDS, poor nighttime sleep, and cataplexy. It has few side effects and very little interaction with other drugs.
The individual must avoid any activity that could pose a health threat, such as using machinery or driving, until any cataplexy is controlled.