Narcolepsy disorders
Introduction
The reason for consultation of the narcoléptic patient is the presence of several short naps at different times of the day (known as sleep attacks);regardless of that I slept enough time during the night. The naps occur involuntarily in situations where the patient is still (mainly sitting) with low motivation for the activities that are being carried out and the environment where he is (for example, watching television);However, sometimes drowsiness puts the patient’s life at risk, since vehicular accidents may occur because the driver can fall asleep.
Introduction
Narcolepsy type 1. It is a disorder caused by a deficiency in the transmission of hypocretin or its production at the hypothalamic level. Its symptoms can basically be grouped into 2 large groups: Excessive diurnal drows. Type 1 narcolepsy has been shown that hypocretin 1 is reduced or absent in cerebrospinal fluid.
Catoplexia is a phenomenon characterized by a brief loss of muscle tone precipitated by emotions and is the most specific data of dwelling of morcolepsy sleep. Not all patients with type 1 narcolepsia have cataplexia;In addition, there may be partial events in which only eyelids, neck or arms muscles are affected by a cataplexia event that affects the whole body at the same time. Many patients with type 1 narcolepsy have alterations in night sleep architecture with frequent awakenings, sleep paralysis and hypnagogical hallucinations.
There are often comorbidities with other sleep and systemic disorders such as obesity as well as psychiatric conditions. The age of onset is between 10 and 25 years of age. The first symptom to manifest is excessive daytime drowsiness while cataplexia develops within the first year, however, it is not uncommon for diagnostic delay to be up to 10 years. Narcolepsy type 2. In this type of narcolepsia catoplexia is not presented and the levels of hypocretin 1 are normal (or, according to the criteria) they have not been measured.
It is estimated that a quarter of narcoleptics belong to this category. Both types share many clinical characteristics such as the age of onset, day and night symptoms except for cataplexia. It is important to consider that up to 10% of patients diagnosed as type 2 initially, they will develop cataplexia defined over time (or if they are evaluated they show hypocretin less than 11 OPG/ml) and it will be necessary to reclassify them as type 1. Etiology. To date there is no specific cause for narcolepsia.
However, it is possible to find a set of genetic, immunological and neurochemical factors that will be discussed below. Genetics. Based on studies, it is known that having a first -degree relative with narcolepsia raises the risk of 10 to 40 times of suffering from narcolepsia. However, also based on monozygotic twin studies, concordance is not absolute, so the conclusion is that in a background of genetic predisposition, environmental factors detonate the beginning of the disease.
Major histocompatibility system. Narcolepsy is one of the diseases with the highest association to specific alleles of the HLA system. In Caucasic and Japanese the most frequent association occurs with type II HLA: DQB1*0602. More than 90% of patients with type 1 narcolepsia have association to this allele while in patients with type 2 narcolepsia only 40% of them have positivity for this allele. This suggests an autoimmune etiology for disease, but greater evidence of the details of this process is still required.
Neurochemicals: The study of the hypocretin/orexin system allows to locate narcolepsia within the group of chronic neurological diseases that have as its origin the deficit of a neurotransmitter. In the dorsal region of the posterior hypothalum. These neurons produce neuromodulators called orexins (for their relationship with appetite control) and also called hypocretins (for their relationship with the incretins).
The hypocretin system has a double function: on the one hand, it is exciter (vigil promoter) and acts in conjunction with other systems such as monoaminergic, dopaminergic, noradrenergic, histaminergic and serotonergic. On the other hand, the hypocretin system seems to have a stabilization function in the Mor/ Vigil sleep transition;Its failure then finally produces failed or incomplete transitions between these sleep phases that generate the symptoms: a) intrusion of muscle atony (typical of the Mor dream) in the vigil that would explain the cataplexia.
Internship of dream activity of the Mor dream in vigil or light sleep which would explain hypnagogical hallucinations;c) Muscle atony intrusion (typical of the Mor dream) in the Dream-Vigilia or vice versa transition, which would explain sleep paralysis. However, alterations in sleep architecture for this reason are more difficult to explain from the pathophysiological point of view, but they certainly contribute to increasing daytime sleepiness. It is also known that there is an increase in the number of awakenings (arousals), Dream Mor without atony.
Coexistence with periodic limb movements and other sleep disorders that further aggravate excessive daytime sleepiness. Diagnosis. Narcolepsy is an exclusion disease when we have ruled out other possible and more frequent causes of hypersomnolence. However, this does not mean that you do not think about it. In a young adolescent or adult patient whose clinimetry does not suspect respiratory sleep disorder and whose history does not suggest insufficient sleep syndrome.
Narcolypsy must be considered initially and intentionally seeking the occurrence of sleep paralysis, hypnagogical hallucinations and cataplexia. The evaluation of excessive daytime sleepiness is carried out through the Epworth Somnolence Scale that has been validated in the Mexican population. The deprivation of sleep must be observed at least by direct sleep newspapers (filled by the patient) and indirect (perceived by the nearest possible caregiver or family). Once insufficient dream is discarded.
conclusion
The next step is to perform standard night polysomnography and the next morning study of multiple nap latencies (MSLT). The determination of hypocretin in cerebrospinal fluid is an invasive procedure and at least in our environment, only available in private laboratories and with a high cost so its use should not be routine except in specific cases of diagnostic doubts. The positivity of the DQB1*0602 allele in the presence of symptoms can support the diagnosis, but its absence does not rule out the disease. In the following table it is possible to observe the criteria for type 1 narcolepsia and type 2.
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