Narcolepsy – Definition, Causes, Types and Symptoms

Narcolepsy is a chronic sleep problem in which the brain is not able to control the sleep-wake cycle. It makes you Narcolepsy - Definition, Causes, Types and Symptoms feel extremely tired, and in severe cases, uncontrollable sudden attacks of sleep during the daytime. The sudden attacks of sleep occur at inappropriate times, like working, talking to someone, driving, having a meal or at school or office.

It is a lifelong sleep disorder, which never goes away. Narcolepsy affects almost all aspects of life. It can be dangerous at times specially with excessive daytime sleepiness or a sleep attack during the day during driving or walking can lead to life risking incidents.1  

This article explores what narcolepsy is, how common it is, its causes, types, main symptoms and diagnosis.

How common is Narcolepsy?

Studies have reported that narcolepsy affects 0.03% to 0.16% of the general population. Although the incidence of narcolepsy is quite less, it is typically presented during childhood, teenagers or young adults and is generally lifelong in nature. The prevalence of narcolepsy with cataplexy varies between 25 and 50 cases per 100000 people.2 Studies have reported that the estimated incidence rate for narcolepsy with cataplexy is 0.74/100,000 per year and for both narcolepsy with cataplexy and narcolepsy without cataplexy is 1.37/100,000 per year. It has also been observed that the incidence rate is highest in the second decade, and is more common in men.3

Causes of narcolepsy

Narcolepsy - Definition, Causes, Types and Symptoms

The cause of narcolepsy is not fully understood. It has been postulated that narcolepsy happens due to the low levels of hormone called hypocretin also known as orexin in brain. It is produced by hypothalamus in brain and influences the functions related to sleep, arousal, appetite and energy expenditure. Genetic predisposition has also been observed, suggesting hereditary causes of narcolepsy (upto 5%). Autoimmune reactions and certain viral infections are also considered as the possible causes of narcolepsy.4

Types of narcolepsy

According to International Classification of Sleep Disorders 3rd edition (ICSD-3) narcolepsy is commonly divided into two types:5

Narcolepsy with cataplexy (Type 1): This type of narcolepsy is characterized by a combination of excessive daytime sleepiness and one or both of the following:

  • With cataplexy: Sudden episodes of complete or partial paralysis of voluntary muscles with onset of sleep.
  • Low or absent hypocretin-1 or orexin levels Narcolepsy - Definition, Causes, Types and Symptoms

Narcolepsy without cataplexy (Type 2): This type of narcolepsy occurs when one has continuous excessive daytime sleepiness but no cataplexy. The patient might take a nap for some hours and wake up refreshed. But after a short period of time, patient may feel tired again.

Diagnosis

The main feature for narcolepsy is the instability between the transition of sleep and wake, as well as the transition between the rapid eye movement (REM) and non-rapid eye movement (NREM) sleep cycles.  Mostly the diagnosis is made only after a serious problem has arisen due to increased episodes of narcolepsy. According to International Classification of Sleep Disorders 3rd edition (ICSD-3), the diagnostic criteria for narcolepsy includes6

Narcolepsy with cataplexy or deficiency of hypocretin-1:

  • Excessive daytime sleepiness at least for 3 months
  • Definite history of cataplexy
  • Onset of REM sleep periods occurs within 15 minutes of falling sleep.
  • Less than 110 picograms/ml values of hypocretin-1 obtained in otherwise normal subjects

Narcolepsy without cataplexy

  • Excessive daytime sleepiness for at least 3 months
  • No signs of typical cataplexy Narcolepsy - Definition, Causes, Types and Symptoms
  • Mean sleep latency of ≤8 min with disrupted REM and NREM sleep cycles

Tests to verify the diagnosis of narcolepsy:7

  • Overnight sleep study (polysomnogram): it is basically a detailed sleep study which requires you to spend the night in a medical facility. You are being monitored during sleep with electrodes under the supervision of a doctor for estimation of brain activity, eye and muscle movement along with heart rate, breathing and rhythm.
  • Sleep history is very important for the diagnosis of narcolepsy, which may include completing a simple questionnaire called Epworth Sleepiness Scale (ESS). You are being asked your sleep patterns in various situations.
  • It is advised to keep a detailed diary of your sleep pattern for about a week. This sleep record will help you to show to your doctor the correlation between your alertness and your sleep pattern.
  • An ActiGraph or other home monitoring system can keep a track of sleep and wake activities. This is done by wearing this device like a wristwatch along with maintaining a sleep diary.
  • Multiple Sleep Latency Test (MSLT): it is a test to measure the sleep latency which basically determines how much time does it take you to fall asleep during the day and how easily you start with rapid eye movement (REM) sleep. This test is often done after PSG.
  • These days hypocretin-1 levels are also used as a diagnostic tool to confirm narcolepsy. Cerebrospinal fluid (CSF) sample drawn from the spinal tap or lumbar puncture can be used to measure hypocretin-1 levels.

Symptoms

Narcolepsy - Definition, Causes, Types and Symptoms Excessive daytime sleepiness: This is considered as the first and most characteristic manifestation of narcolepsy. The patient generally report frank sleep attacks, falling asleep for seconds or minutes and describing these episodes refreshing.4 It is difficult for a person to stay awake during the daytime even after getting enough sleep at night. Narcoleptic patients can sleep at inappropriate times, such as while driving, talking to someone, eating, working or at school. Excessive daytime sleepiness is the most common symptom of narcolepsy and presented by almost every patient. According to ICSD-3, the diagnosis of both type-1 and type-2 narcolepsy is primarily based on the presence of excessive daytime sleepiness for at least 3 months or more.5

Cataplexy: These are sudden emotionally triggered episodes of muscle weakness with preserved consciousness. The episodes are generally triggered by strong positive or negative emotions such as laughing at a joke, unexpected encounter with a friend, in some cases frustration or anger. It generally evolves in seconds of time, first involving the face and neck and weakening the muscles of trunk and limbs, sparing the muscles involved in breathing, causing the person to slump on ground, fully conscious but unable to move for as long 1 or 2 minutes. Partial or incomplete cataplexy is usually characterized by slurring of speech and sagging of face. In children, this can have long lasting periods of low muscle tone, with wobbly gait and involvement of perioral muscles movements such as tongue protrusion and grinning expressions. A patient history of episodic event of cataplexy is very helpful in the diagnosis of narcolepsy specially in type 1.7

Hallucinations: Hallucinations are presented by 30-60% of the narcolepsy cases. They may occur at the onset or offset of sleep and can be random and frightening for the patient. Patients usually report visual hallucinations. Narcolepsy - Definition, Causes, Types and Symptoms Occasionally, some patients present with unusual or out of body experiences explaining themselves floating while sleeping.1

Sleep paralysis: Sleep paralysis is presented by 25-50% of the patients which could be complete or partial but the patient is fully conscious. This is usually reported by patient as inability to move or talk. It lasts for about very short periods of time not more than couple of minutes. Sleep paralysis is usually accompanied by hallucinations. This can result in frightening experience of physical or sexual assault. Despite sparing the breathing muscles, some patients complain of shortness of breath or asphyxiation contributing towards the terrifying nature of the episodes.4

Other features of narcolepsy include, disrupted sleep at night, behavioral disturbances, loss of concentration, memory impairment, and blurry vision. The classical tetrad presentation of excessive daytime sleepiness, cataplexy, hallucinations and sleep paralysis is usually variable in terms of concurrent occurrence and intensity and presented only about by 10% of the patients.3

Treatment options:             

There is no permanent cure for narcolepsy. It is a lifelong chronic sleep disorder. Narcolepsy is managed by the combination of behavioral and therapeutic therapy. The right treatment for narcolepsy depends upon the symptoms and severity of disease.1

Behavioral therapy:

The first step towards the management of narcolepsy is the lifestyle modifications. This is an equally important approach for patients suffering from narcolepsy or any other sleep related disorder.1

Following are some of the lifestyle changes that can help in the management of narcolepsy:1 Narcolepsy - Definition, Causes, Types and Symptoms

  • Try to follow proper sleep hygiene, for starters try to sleep and wake at the same time everyday even on weekends
  • Try to get enough sleep at night that is at least 8 hours of sleep for adults.
  • Schedule two 10-15 mins naps during the daytime to keep yourself fresh
  • Do some form of exercise everyday
  • Avoid intake of stimulants like alcohol, caffeine, tobacco or any kind of drugs close to bed-time
  • Try to reduce device time to as minimum as possible
  • Inform your colleagues and employer about your condition in case you fall asleep on work.

Pharmacological management

Behavioral or lifestyle modifications usually seem insufficient in controlling the symptoms of excessive daytime sleepiness in narcolepsy. There are some medications that can help in reducing the symptoms of narcolepsy:1,5

  • Stimulants or wakefulness promoting agents: These are medications that can help in reducing the excessive daytime sleepiness such as methylphenidate, dextroamphetamine and nonamphetamine and wakefulness promoting agents like modafinil and armodafinil. In case of any underlying medical problem such as heart disease or abnormal heart rhythms, then you may not be able to take these medications.
  • Serotonin-norepinephrine reuptake inhibitors (SNRIs): SNRIs such as venlafaxine (Effexor) can be used to treat cataplexy, hallucinations, and sleep paralysis. Problems with digestion, weight gain and insomnia are various side effects seen.
  • Selective serotonin reuptake inhibitors (SSRIs): SSRIs such as fluoxetine (Prozac) can also help in regulating sleep and improve your mood. However, side effects such as light headedness and dry mouth are common. Narcolepsy - Definition, Causes, Types and Symptoms
  • Tricyclic antidepressants: Although these were actually developed for treating depression, certain antidepressant medications such as amitriptyline and nortriptyline have been found to be effective at decreasing cataplexy, sleep paralysis, and the hallucinations associated with narcolepsy. Untoward side effects, of dryness of mouth, constipation along with retention of urine can be seen.
  • Sodium oxybate: Sodium oxybate is considered as a standard therapy for the symptoms of cataplexy and excessive daytime sleepiness by the American Academy of Sleep Medicine.
  • Hypocretin agonists (hormone analogue) are also used as emerging drugs in the treatment of narcolepsy.
  • Pitolisant (Wakix): Wakix increases the release histamines in the brain to decrease daytime sleepiness. It’s been recently FDA-approved to treat narcolepsy. Side effects of insomnia with anxiety, headache and nausea are seen.

One of the major problems with these drugs is the development of tolerance, which requires escalating doses causing ineffectiveness even at higher doses.

Conclusion

Narcolepsy is a chronic lifelong sleep disorder characterized by sudden episodes of sleep at inappropriate times during the day. There are still several unanswered questions about narcolepsy. Living with narcolepsy can be difficult in multiple ways as it affects basic functions due to disrupted sleep at night and excessive daytime sleepiness. The correct and timely diagnosis, lifestyle modifications and drugs can easily manage narcolepsy.

FAQ’s

What is narcolepsy?

Narcolepsy is a chronic sleep disorder characterized by sudden episodes of sleep due to the disruption in sleep-wake cycles of REM sleep. Narcolepsy - Definition, Causes, Types and Symptoms

What are the common symptoms of narcolepsy?

Narcolepsy is mainly characterized by excessive sleepiness during the daytime. It is also presented by cataplexy (paralysis of voluntary muscles), hallucinations and sleep paralysis (during sleep onset and offset).

What triggers narcolepsy with cataplexy attacks?

An attack of narcolepsy is usually triggered by the strong positive or negative emotions such as laughing on jokes or anger or frustration.

What is the classical tetrad of narcolepsy?

The classical tetrad of narcolepsy involves excessive daytime sleeping, cataplexy, hypogogic hallucinations and sleep paralysis.

Is cataplexy dangerous?

Cataplexy is generally not dangerous. The attacks of cataplexy usually last from few seconds to minutes and are usually not dangerous for the patient.

How common is it?

Narcolepsy affects 0.03% to 0.16% of the general population. It is usually not very common in adult population. It is not rare but usually misdiagnosed until the first symptoms appear. The prevalence of narcolepsy with cataplexy varies between 25 and 50 cases per 100000 people.

Who is most commonly affected by narcolepsy?

Although the incidence of narcolepsy is quite less, it typically presents during childhood, in teenagers or young adults and is generally lifelong in nature. The attacks of narcolepsy usually happen between the age groups Narcolepsy - Definition, Causes, Types and Symptoms of 10-25 years.

How does the attack of narcolepsy feel like?

During the attack of narcolepsy, due to the sudden loss of voluntary muscle control, patients feel unable to move, unreal sensations due to hallucinations and total paralysis just before falling asleep or just after getting up.

Is it legal to drive with confirmed diagnosis of narcolepsy?

It is safe to drive under good and controlled conditions. People with narcolepsy should avoid long drives. They can safely drive around the city for around 30 minutes and should avoid long boring highways.

What are treatment options for narcolepsy?

There is still no confirmed treatment for narcolepsy. Symptomatic management should be done with behavioral and therapeutic methods.

How many hours of sleep does a narcolepsy patient need?

Patient suffering from narcolepsy feel tired all the time and sleep longer than the normal healthy individuals. They may get ten hours of sleep every night but still feel tired all the day.

References

  1. Gradney S, Sigua NL. What is Narcolepsy? Am J Respir Crit Care Med. 2017 Mar 1;195(5): P9-P10. doi: 10.1164/rccm.1955P9.
  2. Raggi A, Plazzi G, Ferri R. Health-Related Quality of Life in Patients with Narcolepsy: A Review of the Literature. J Nerv Ment Dis. 2019 Feb;207(2):84-99. doi: 10.1097/NMD.0000000000000918.
  3. Akintomide GS, Rickards H. Narcolepsy: a review. Neuropsychiatr Dis Treat. 2011; 7:507-18. doi: 10.2147/NDT.S23624.
  4. Leschziner G. Narcolepsy: a clinical review. Pract Neurol. 2014 Oct;14(5):323-31. doi: 10.1136/practneurol-2014-000837.
  5. Zhang J, Han F. Sleepiness in Narcolepsy. Sleep Med Clin. 2017 Sep;12(3):323-330. doi: 10.1016/j.jsmc.2017.03.008.
  6. Reading PJ. Update on narcolepsy. J Neurol. 2019 Jul;266(7):1809-1815. doi: 10.1007/s00415-019-09310-3.
  7. Scammell TE. Narcolepsy. N Engl J Med. 2015 Dec 31;373(27):2654-62. doi: 10.1056/NEJMra1500587.
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