Among the sleep disorders the case of narcolepsy is particularly striking because of the specificity of its symptoms, caused by biological factors and related to alterations in sleep and wakefulness.

We will now look at the nature of narcolepsy, the types it is divided into, the most recent findings regarding this disease, and the most effective treatments for its symptoms.

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 disturbed sleep patterns.

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 and is equally common in women and men.

This disorder can interfere very significantly with the lives of those who suffer from it: not only are they affected professionally by hypersomnolence and often seen as lazy because of their social environment, but there is also an increased risk of falls and road or other accidents.

Symptoms and signs

According to the DSM-5 manual, the fundamental symptom of narcolepsy is the sudden sleepiness that occurs during the day even though the person has slept adequately, especially after large meals, due to stress or intense emotions. To make the diagnosis, these episodes must have occurred three times a week during the previous three months.

In addition to the ‘sleep attacks’ , the presence of cataplexy is required, a deficit in the hormone orexin or a disturbance in the sleep phases, particularly REM or REMB (rapid eye movement sleep); for example, more movements and waking up occur 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, laughter, or crying, and when it occurs the person maintains consciousness even though they have difficulty speaking and their vision becomes blurred.

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

In people with narcolepsy it is common for the first period of REM sleep to appear 15-20 minutes after falling asleep , while under normal conditions the REM phase does not appear until an hour and a half later. Sleep disturbances are analysed by means of nocturnal polysomnography and the multiple sleep latency test, which assesses a person’s ability to fall asleep.

The Narcoleptic Tetrad

Before the biological basis of narcolepsy was well known, it was usually diagnosed on the basis of four symptoms that were considered cardinal: daytime hypersomnolence, cataplexy, hypnagogic hallucinations and sleep paralysis .

Hypnagogic hallucinations and sleep paralysis 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 we often see incomplete and static images and hear sounds like buzzing or fragments of dialogue, similar to the phenomena that occur during dreams; these are hypnagogic hallucinations. There are also hypnopompic hallucinations, which occur when we go from sleep to wakefulness.

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. This is an anxious experience , partly because during REM sleep breathing is rapid and shallow, which gives the person the feeling that they are suffocating.

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

Causes of this disorder

Narcolepsy is a disease of genetic origin with a hereditary component : 10 – 20% of narcoleptic people have at least one first-degree relative who also has the disorder. However, given the variability of cases, no single cause has been determined.

Non-genetic factors may also be relevant in the development of secondary narcolepsy, for example brain injury, 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 the HLA (human leukocyte antigens), which are fundamental in the immune response.

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

Types of Narcolepsy

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

In addition to the types we will define below, the DSM-5 differentiates cases of narcolepsy into mild, moderate and severe according to the frequency of cataplexy, the need for naps, disturbed nighttime sleep and the effectiveness of the medications.

1. No cataplexy and hypocretin deficit

In this subtype a deficit of the hormone orexin and an alteration of the phases of sleep are confirmed but no episodes of cataplexy occur .

2. With cataplexy and without hypocretin deficit

Unlike the previous case, in addition to the REM disorders, cataplexy occurs but the levels of orexin in the cerebrospinal fluid are normal . This 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 DNA exon 21. The onset of these cases is late , usually occurring between the ages of 30 and 40.

The term “ataxia” refers to a lack of motor coordination , in this case caused by an alteration of the cerebellum. In addition to ataxia, deafness and narcolepsy, dementia usually develops in this subtype 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 other medical condition

In some cases narcolepsy appears as a 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, the treatment of this disorder is symptomatic . However, there are effective options for relieving all symptoms, so many people with narcolepsy can lead normal lives.

Various medications are used to control cataplexy: tricyclic antidepressants, modafinil, sodium oxybate, and selective serotonin and noradrenaline reuptake inhibitors such as fluoxetine and venlafaxine, which also reduce hypnagogic hallucinations and sleep paralysis.

Stimulant drugs such as modafinil and methylphenidate, known for their use in Attention Deficit Hyperactivity Disorder (ADHD), are effective in reducing drowsiness, although the effect usually requires a progressive increase in dose to be maintained; this carries a greater risk of side effects.

It has been suggested that a combination of tricyclic stimulants and antidepressants may be the most appropriate approach, although treatment should differ according to the individual’s specific symptoms.

Likewise there are treatments that focus on the hormone hypocretin , currently in the research phase. These include immunotherapy, gene therapy and orexin replacement.

Psychological interventions

Psychoeducational programs are very effective in cases of narcolepsy. Specifically, it is useful to transmit information and advice to the person diagnosed and to his/her family and professional environments to improve his/her functioning and well-being. Support groups can also be very useful for people with this problem.

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

It is also important to maintain an adequate sleep hygiene : keep a regular schedule, avoid smoking, eat a lot or drink stimulating drinks about 3 hours before bedtime, practice daily exercise, do relaxing activities just before going to bed, etc.