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Narcolepsy

Definition

Narcolepsy falls under the hypersomnia classification of sleeping disorders. People with narcolepsy often have similar symptoms to those suffering from forms of hypersomnia like excessive daytime sleepiness. However, they also experience additional symptoms such as cataplexy (episodes of muscle weakness), sleep hallucinations, and/or sleep paralysis.

There are two types of narcolepsy. Type I narcolepsy (also known as narcolepsy with cataplexy) includes excessive daytime sleepiness, cataplexy, sleep paralysis, and hallucinations.

Type II narcolepsy (also known as narcolepsy without cataplexy) also involves excessive daytime sleepiness but does not necessarily include cataplexy or the presence of sleep paralysis or hallucinations. The frequency and kind of additional symptoms experienced helps physicians  determine which type of narcolepsy is affecting the individual.

What is Narcolepsy?

Narcolepsy is a neurological disorder within the hypersomnia classification of sleeping disorders. Akin to other disorders within the hypersomnia family, excessive daytime sleepiness is a major symptom that occurs despite awakening well rested and refreshed following adequate sleep. For many, nighttime sleep can be disturbed and fragmented from frequent waking; difficulty returning to sleep adds to the sleep disruptions. Other symptoms include sleep-related hallucinations, sleep paralysis and abnormal timing or misalignment of REM sleep within a sleeping period. Narcolepsy and its symptoms can have a significant impact on the quality of life for those experiencing it making daily functions like driving, attending school or performing at work challenging.

Symptoms of Narcolepsy

Excessive Daytime Sleepiness: Excessive Daytime Sleepiness (EDS) is a highly prevalent symptom for those with narcolepsy. EDS is extreme and abnormal sleepiness. Those experiencing EDS have difficulty maintaining wakefulness at times when they should be alert and often have unintended or unplanned periods of intense drowsiness or short bursts of sleep known as “sleep attacks.” Sleep attacks are restorative in nature, similar to sleep acquired during regular sleep. However, the benefits do not often last long and excessive sleepiness returns.

Cataplexy: Cataplexy is a symptom specific to Type I Narcolepsy. It involves an abrupt, sudden loss of muscle tone while the person is awake and commonly has emotional triggers. Strong emotions such as excitement or laughter, anger, fear or even stress can all produce a cataplexic episode. Cataplexy is often described as a sensation of weakness or the inability to control voluntary muscles. Such sudden attacks can last for a few seconds or several minutes before resolving.

Hallucinations: Realistic, vivid and frequently frightening hallucinations are another notable characteristic of narcolepsy. Seeing, hearing or even feeling things that are not really present are common experiences. Hypnagogic hallucinations occur when the person is progressing from a state of wakefulness to sleep. Hypnopompic hallucinations occur while a person is transitioning from sleep to wake.

Sleep Paralysis: Sleep paralysis, as the name suggests, is a form of paralysis that can occur during sleep/wake transitions. It is a temporary state lasting for a few seconds or minutes whereby the person affected has complete awareness and consciousness yet is unable to speak or move. Though benign in nature, it can be a frightening experience, especially if it happens in combination with hallucinations.

The sleep paralysis that narcoleptics experience is the same as that associated with REM sleep. As a protective measure, the body goes into a state of low muscle tone or atonia during REM (Rapid Eye Movement) to stop someone from acting out their dreams. Due to the abnormal timing of REM sleep in those with narcolepsy, sleep paralysis can appear at inappropriate times in the sleep cycle.

Fragmented Sleep: Disruptions in sleep can involve frequent movements, vivid dreams, periods of wakefulness, and difficulty returning to sleep following a period of wakefulness. Persistent interruptions in sleep can lead to an incomplete night of sleep leaving those affected extremely exhausted.

How Common is Narcolepsy?

Narcolepsy is a relatively rare disorder affecting approximately 1 in 2,000 people. For many, onset commonly occurs in the pre-teen to teenage years but it can certainly occur within the early twenties and beyond. Both men and women are equally affected. Estimates of those with narcolepsy can be difficult to compute because many cases are underdiagnosed or misdiagnosed before being properly recognized.

What Causes Narcolepsy?

Categorized as a neurological disorder, narcolepsy with cataplexy is the result of abnormalities in brain chemistry, specifically a neurotransmitter called hypocretin. Hypocretin (also known as orexin) is a chemical found in the hypothalamus that works to regulate REM sleep and to promote wakefulness.

For those with narcolepsy with cataplexy, hypocretin levels are significantly lower than normal values. Abnormalities in the immune system mistakenly attack the healthy neurons producing hypocretin, resulting in less being produced and present in the brain. The reduction of hypocretin causes the common symptoms of excessive daytime sleepiness and misaligned occurrences of REM sleep. Therefore, narcolepsy with cataplexy is the result of an autoimmune disorder.

Family history may also play a role in the presence of narcolepsy, though most cases occur spontaneously.

In some rare instances, narcolepsy can occur as a result of traumatic brain injury to the area of the brain regulating REM sleep or other neurological disorders affecting the same area of the brain.

More research is needed to determine the causes of narcolepsy without cataplexy.

Diagnosis of Narcolepsy

A comprehensive medical history, examination, and use of a sleep journal are key components when diagnosing narcolepsy. A full medical history and physical examination can provide possible alternatives to excessive sleepiness. The sleep journal may assist the physician in reviewing symptoms and symptom onsets, with cataplexy being most notable. There are 2 diagnostic tests commonly utilized in determining the existence of narcolepsy.

Polysomnogram – An overnight polysomnogram or sleep study is an extensive diagnostic tool for physicians. Electrodes applied to the head record brain wave activity as the person goes into and out of different stages of sleep. Other electrodes record eye movements, existence of snoring, breathing patterns and muscle activity that may occur while the person sleeps. Physicians use the polysomnogram to rule out other disorders such as obstructive sleep apnea or primary snoring.

Multiple Sleep Latency Test (MSLT) – A multiple sleep latency test occurs the day following an overnight sleep study. The test begins approximately two hours following the conclusion of the polysomnogram. While most of the electrodes and wires from the previous night are removed, those recording brain wave activity remain to determine sleep onset.

An MSLT consists of five napping opportunities throughout the day spaced at two hour intervals. The purpose is to monitor the length of time to sleep onset and REM onset. If no sleep is observed, the nap concludes after 20 minutes. If sleep does occur, sleep onset time is noted and the nap concludes 15 minutes after sleep onset. Sleep onset averaging less than eight minutes over the course of the MSLT indicates excessive daytime sleepiness. REM onset that occurs in at least two of the nap opportunities provides a clear picture for the diagnosing physician.

In some cases, physicians may request a sample of cerebrospinal fluid to be analyzed for the amount of hypocretin present. This is done by lumbar puncture or spinal tap to remove some of the cerebrospinal fluid. Low levels of hypocretin commonly indicate narcolepsy.

Treatment

There is no cure for narcolepsy, however the symptoms can be managed once diagnosis is determined. Medications and lifestyle changes are the most successful at managing the symptoms accompanying narcolepsy.

Medications commonly prescribed vary depending on the symptoms, existence of cataplexy and personal preference for best results. Medications can include stimulants, antidepressants, and sedatives.

Stimulants are prescribed to promote wakefulness and decrease the main symptom of narcolepsy, excessive daytime sleepiness. Modafinil (also known as Provigil and Nuvigil) is a newer medication, and is commonly used first due to it being less addictive than older stimulants. There are also less side effects when Modafinil is used.

Other amphetamine-like stimulants can also be used in treating excessive daytime sleepiness associated with narcolepsy. Unlike Modafinil, amphetamine-like stimulants can have side effects like nervousness or disruptions in sleep. They are also a class of drugs with the potential of abuse if not monitored closely by a physician.

Antidepressants can also be used in the treatment of narcolepsy, specifically in those with Type I with cataplexy. Tricyclic and SSRIs (Selective Serotonin Reuptake Inhibitors) are commonly used and include medications like clomipramine, fluoxetine, and atomoxetine.

Sodium oxybate is another source for treatment of narcolepsy with cataplexy. It is a strong sedative used to promote better sleep quality at night and when prescribed is taken twice a night. Given the strength of the medication and concerns over safety, sodium oxybate is restricted and monitored closely.

Lifestyle changes include changing daily behaviors to promote better, more restorative sleep. Such changes can include maintaining a regular sleep-wake schedule, avoiding caffeine or alcohol prior to going to bed, exercise, avoiding smoking and restorative naps during the day.

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