Narcolepsy: types, causes, symptoms, and treatment

Between sleep disorders the case of narcolepsy is especially striking due to the specificity of its symptoms, caused by biological factors and related to alterations in sleep and wakefulness.

Next we will analyze the nature of narcolepsy, the types into which it is divided, the most recent discoveries regarding this disease and the most effective treatments to combat Your symptoms.

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What is narcolepsy?

Narcolepsy, also known as "Gélineau syndrome", is a neurological sleep disorder that produces excessive daytime sleepiness, as well as other symptoms associated with disturbances in sleep rhythms.

The term 'narcolepsy' was coined by Jean-Baptiste-Édouard Gélineau, who first described this syndrome in 1880. It comes from the Greek words ‘narkē’ and ‘lepsis’ and can be translated as ‘sleep attack’.

It is usually detected between the ages of 7 and 25, although some subtypes of narcolepsy have a later onset. It occurs in approximately 0.1% of the population, being just as common in women and men.

This disorder can interfere in a very significant way in the lives of those who suffer from it: they are not only affected on a professional level by hypersomnolence and they are usually seen as lazy people due to their social environments, but there is a greater risk of falling and traffic accidents or other kind.

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Symptoms and signs

According to the DSM-5 manual, the fundamental symptoms of narcolepsy are sudden bouts of sleep that occur during the day even if the person has slept adequately, especially after heavy meals, stress or intense emotions. To make the diagnosis it is necessary that these episodes have occurred three times a week during the previous three months.

In addition to the 'sleep attacks' the presence of cataplexy is required, a deficiency in the hormone orexin or an alteration in sleep phases, particularly REM or REM (rapid eye movement sleep); for example, there are more movements and awakenings during the night.

Cataplexy or cataplexy is a specific symptom of narcolepsy that consists of episodes of loss of muscle tone throughout the body, which can lead to falls. Cataplexy is usually triggered by strong emotions such as fear, laughing, or crying, and when occurs the person maintains consciousness although he has difficulty speaking and his sight.

Orexin, or hypocretin, is involved in alertness and wakefulness, as well as in food intake. This hormone is secreted by the hypothalamus. In many cases of narcolepsy, a low level of hypocretin is detected in the cerebrospinal fluid.

In people with narcolepsy it is common that the first period of REM sleep appears 15-20 minutes after falling asleep, while in normal conditions the REM phase does not appear until an hour and a half passes. Sleep disturbances are analyzed using nocturnal polysomnography and the multiple sleep latency test, which assesses how easy it is to fall asleep.

The narcoleptic tetrad

Before the biological bases of narcolepsy were well known, it used to be diagnosed based on four symptoms that were considered cardinal: daytime hypersomnolence, cataplexy, hypnagogic hallucinations, and sleep paralysis.

Hypnagogic hallucinations and sleep paralysis they are non-pathological phenomena that occur in the transition between wakefulness and sleep. They occur more frequently in people with narcolepsy and, like cataplexy, are associated with REM phase intrusions.

When we are about to fall asleep many times we see incomplete and static images and we hear sounds such as buzzes or fragments of dialogue, similar to the phenomena that occur during dreams; these are hypnagogic hallucinations. There are also hypnopomics, which occur when passing from sleep to wakefulness.

For its part, sleep paralysis can occur when we fall asleep or wake up and is characterized by the sensation of being awake but without the ability to move or make sounds. It is an anxious experience, in part because during REM sleep, breathing is rapid and shallow, which makes the person feel as if they are suffocating.

Only one in four people with narcolepsy have all the symptoms of narcoleptic tetrad simultaneously. Hypersomnolence is usually the first symptom and persists throughout life, while intrusions from REM sleep can disappear over time.

Causes of this disorder

Narcolepsy is a disease of genetic origin with a hereditary component: between 10 and 20% of narcoleptic people have at least one first-degree relative who also has the disorder. However, given the variability of the cases, a single cause could not be determined.

Non-genetic factors may also be relevant in the development of secondary narcolepsy, for example brain injuries, infections, contact with pesticides, hormonal changes, stress or certain types of diet.

This disorder has been mainly related to a genetic alteration in the chromosomes that determine HLA antigens (human leukocyte antigens), essential in the response immune.

In many cases of narcolepsy, low levels of the hormone hypocretin or orexin are seen in the cerebrospinal fluid. Orexin deficiency is more common in people with cataplexy and is generally due to to the destruction of the neurons of the hypothalamus that produce it as a consequence of the genetic, biological and environmental factors mentioned previously. This alteration is believed to be caused by an autoimmune reaction.

Types of narcolepsy

DSM-5 describes different types of narcolepsy, categorizing them based on biological signs and underlying causes, as well as associated symptoms.

In addition to the types that we will define below, the DSM-5 differentiates the cases of narcolepsy into mild, moderate and severe depending on the frequency of cataplexy, the need for naps, the alteration of night sleep and the effectiveness of the medicines.

1. Without cataplexy and with hypocretin deficiency

In this subtype, a deficiency of the hormone orexin and an alteration of the sleep phases are confirmed but cataplexy episodes do not occur.

2. With cataplexy and without hypocretin deficiency

Contrary to the previous case, in addition to REM alterations, cataplexy occurs but orexin levels in cerebrospinal fluid are normal. It is a rare type that includes less than 5% of cases of narcolepsy.

3. Autosomal dominant cerebellar ataxia, deafness, and narcolepsy

The cause of this type of narcolepsy is considered to be a mutation of exon 21 of the DNA. The onset of these cases is late, normally occurring between the ages of 30 and 40.

The term "ataxia" refers to the lack of motor coordination, in this case caused by an alteration of the cerebellum. In addition to ataxia, deafness, and narcolepsy, this subtype usually develops dementia as the disease progresses.

4. Autosomal dominant narcolepsy, obesity, and type 2 diabetes

This subtype is determined by a mutation of oligodendrocytes, glial cells involved in the formation of myelin, a substance that increases the speed of nerve transmission. In these cases there is also a low concentration of hypocretin in the cerebrospinal fluid.

5. Secondary to another medical condition

In some cases narcolepsy appears as direct consequence of tumors, trauma, or infections (such as sarcoidosis or Whipple's disease) that destroy orexin-secreting cells.

Treatment of narcolepsy

Since narcolepsy is not curable, treatment of this disorder is symptomatic. However, there are effective options to alleviate all symptoms, so many people with narcolepsy can lead normal lives.

Different medications are used to control cataplexy: antidepressants tricyclics, modafinil, sodium oxybate, and selective serotonin reuptake inhibitors and noradrenaline, such as fluoxetine and venlafaxine, which also reduce hypnagogic hallucinations and paralyzes of the dream.

Stimulant drugs such as modafinil and methylphenidate, known for its use in the Attention Deficit Hyperactivity Disorder (ADHD), are effective in reducing drowsiness, although for the effect to be maintained it is usually necessary to progressively increase the dose; This carries an increased risk of side effects.

It has been suggested that the most appropriate approach may be the combination of stimulants and tricyclic antidepressants, although treatment should be different depending on the specific symptoms of the person.

In addition there are treatments that focus on the hormone hypocretin, currently under investigation. These include immunotherapy, gene therapy, and orexin replacement.

Psychological interventions

Psychoeducational programs are very effective in cases of narcolepsy. Specifically, information and advice should be transmitted to the person diagnosed and to their family and professional environments to improve their functioning and well-being. Support groups can also be very helpful for people with this problem.

Scheduling one, two, or three naps 10-30 minutes during the day greatly alleviates hypersomnolence and improves academic and work performance. This treatment is considered to be in the experimental phase, although the results are promising.

It is important too maintain proper sleep hygiene: keep regular hours, avoid smoking, eat a lot or drink stimulant drinks about 3 hours before sleeping, exercising daily, doing relaxing activities just before bedtime, etc.

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