Among 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.
Below 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 its symptoms.
narcolepsy, Also known as “Gélineau syndrome”is a neurological sleep disorder that produces excessive daytime sleepiness, as well as other symptoms associated with alterations 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 7 and 25 years of age.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 in the lives of those who suffer from it: not only are they affected professionally by hypersomnolence and are often seen as lazy people due to their social environments, but there is a greater risk of suffering falls and traffic or other accidents.
Symptoms and signs
According to the DSM-5 manual, the fundamental symptom of narcolepsy is sudden bouts of sleep that occur during the day even if the person has slept adequately, especially after heavy meals, due to 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 ‘sleep attacks’ the presence of cataplexy is requireda 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, laughter or crying, and when it occurs the person maintains consciousness although they have difficulty speaking and their vision becomes blurred.
Orexin, or hypocretin, It is involved in alertness and wakefulnessas well as in food intake. This hormone is secreted by the hypothalamus. In many cases of narcolepsy, a low concentration of hypocretin is detected in the cerebrospinal fluid.
In people with narcolepsy it is common the first period of REM sleep appears 15-20 minutes after falling asleepwhile under normal conditions the REM phase does not appear until an hour and a half has passed. Sleep disturbances are analyzed using nocturnal polysomnography and the multiple sleep latency test, which assesses the person’s ease of falling asleep.
The narcoleptic tetrad
Before the biological bases of narcolepsy were well known, it was usually diagnosed based on 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. In people with narcolepsy they occur more frequently and, like cataplexy, are related to intrusions of the REM phase.
When we are about to fall asleep we often see incomplete and static images and hear sounds such as humming or fragments of dialogue, similar to the phenomena that occur during dreams; These are hypnagogic hallucinations. There are also hypnopompic symptoms, which occur when going from sleep to wakefulness.
For its part, sleep paralysis can occur when we fall asleep or when we wake up and is characterized by the sensation of being awake but without the ability to move or make sounds. It is an anxiety-inducing experience.partly because during REM sleep breathing is rapid and shallow, which makes the person feel like they are suffocating.
Only one in four people with narcolepsy present all the symptoms of the narcoleptic tetrad simultaneously. Hypersomnolence is usually the first symptom and persists throughout life, while REM sleep intrusions may disappear over time.
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 cases, a single cause has not been 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 the HLA antigens (human leukocyte antigens), essential in the immune response.
In many cases of narcolepsy, low levels of the hormone hypocretin or orexin are observed in the cerebrospinal fluid. Orexin deficiency is more common in people with cataplexy and is generally due to to the destruction of the neurons in the hypothalamus that produce it as a consequence of the genetic, biological and environmental factors mentioned previously. It is believed that this alteration is caused by an autoimmune reaction.
Types of narcolepsy
The DSM-5 describes different types of narcolepsycategorizing them based on 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 based on the frequency of cataplexy, the need for naps, nighttime sleep disturbance, and the effectiveness of medications.
1. Without cataplexy and with hypocretin deficiency
In this subtype, a deficiency of the hormone orexin and an alteration of sleep phases is confirmed, but no episodes of cataplexy occur.
2. With cataplexy and without hypocretin deficiency
Unlike in the previous case, in addition to the REM alterations, cataplexy occurs but orexin levels in the cerebrospinal fluid are normal. This is a rare type that includes less than 5% of narcolepsy cases.
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 DNA. The onset of these cases is latenormally occurring between 30 and 40 years of age.
The term “ataxia” refers to the lack of motor coordinationin 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 due to a mutation of oligodendrocytesglial 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.
Narcolepsy treatment
Since narcolepsy is not curable, The treatment of this disorder is symptomatic. However, there are effective options to relieve all symptoms, so many people with narcolepsy can lead a normal life.
Different medications are used to control cataplexy: tricyclic antidepressants, modafinil, sodium oxybate, and selective serotonin and norepinephrine 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 for the effect to be maintained it is usually necessary to progressively increase the dose; This carries a higher risk of side effects.
It has been suggested that the most appropriate approach may be a combination of stimulants and tricyclic antidepressants, although the treatment should be different depending on the person’s specific symptoms.
In addition There are treatments that focus on the hormone hypocretincurrently 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 advisable to transmit information and advice to the diagnosed person and 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 relieves hypersomnolence and improves academic and work performance. This treatment is considered to be in the experimental phase, although the results are promising.
It is also important maintain adequate sleep hygiene: keep regular schedules, avoid smoking, eat a lot or drink stimulating drinks about 3 hours before going to sleep, exercise daily, do relaxing activities just before going to bed, etc.
