Cataplexy is a neurological syndrome characterized by a sudden loss of muscle tone when experiencing strong emotions. The attack occurs against the background of laughter, anger or fear. Focal muscle weakness is accompanied by the loss of functions of a body part (arms, legs, neck), complete – the fall of a person and short-term immobility. A clinical and anamnestic method is used for diagnosis: observation, survey, analysis of video recordings. Treatment involves taking medications, observing the sleep-wake regime.
G47.4 Narcolepsy and cataplexy
The term “cataplexy” in translation from ancient Greek means “horror”, “fear”, “confusion”. Synonymous names of the syndrome are affective loss of muscle tone, blockade of tone, affective adynamia, emotional asthenia. The course is chronic. The debut is more likely to occur at a young or teenage age. As you get older, seizures become more rare and less intense. The prevalence is about 20 cases per 100,000 people. Men are more susceptible to the syndrome.
Cataplexy is based on organic damage to the central nervous system, prolonged mental stress, and the effects of toxins on the body. Predisposing factors include chronic intoxication with alcohol or narcotic substances, being in the zone of a man-made disaster or military operations, severe fright. An attack of loss of muscle tone is a syndrome that occurs in a number of diseases:
- Narcolepsy type I. This pathology is the cause of more than 90-92% of cases of cataplexy. It is characterized by pathological daytime drowsiness with attacks of sudden falling asleep. The basis of the phenomena is a neurochemical violation of the basics of regulating the sleep and wakefulness cycle.
- Hereditary diseases. In Niemann-Pick type C disease, cataplexy is manifested by weakness of the muscles of the jaws, neck, legs, and is more often found in adolescents. With Prader-Willi syndrome, attacks of atony are rare, develop as manifestations of secondary narcolepsy.
- Brain diseases. The cause of cataplexy may be transient ischemia or compression of the brain stem. The attack unfolds in patients with cervical osteochondrosis, stenosing lesion of the vertebral arteries, vascular or tumor formations. Muscular atony occurs after reclining and sharp turns of the head.
The etiology of narcolepsy is a violation of the biochemical and neurological foundations of the regulation of sleep-wake cycles. The pathogenetic cause of cataplexy in narcolepsy of the first type is insufficient production of the neurotransmitter orexin A and B. According to its chemical structure, it is a peptide, the precursor of which is the protein pre-progypocretin. Its physiological function is to provide vigor and maintain appetite.
Orexinergic neurons are few in number, concentrated mostly in the hypothalamus (about 10-20 thousand cells secreting a neurotransmitter). Their activity in patients with cataplexy is reduced. The causes continue to be investigated, the most likely hypothesis is an autoimmune lesion. According to laboratory tests, the level of orexin A in the cerebrospinal fluid (less than 110 pg/ml) and in the blood (below 0.5 pg/ml) was lowered.
The axons of orexinergic neurons branch strongly, innervate cells of various parts of the brain that produce acetylcholine, glutamic acid, serotonin. These neurotransmitters cause the nervous system to be excited. Their insufficiency is manifested by fatigue, drowsiness, depression.
The syndrome is characterized by attacks of muscle atony, lasting from 5-10 seconds to several minutes. Provoking factors are strong emotions: in 90% of cases – laughter, less often – fear, anger, surprise. Consciousness remains clear, the loss of tone is bilateral, may affect isolated muscle groups or muscles of the whole body. Depending on this, there are two types of cataplexy: focal and classical.
With focal cataplexy, the mechanics of the actions performed are violated. If the leg muscles weaken, a walking or standing person falls to his knees. With a decrease in tone in the neck area, the head involuntarily falls on the chin, nodding movements occur. If the pathology affects the muscles of the face, the lower jaw drops during an attack, the eyelids close or speech becomes slurred. Sometimes there are muscle twitches.
Focal cataplexy attacks may remain invisible to others, but the classic version of the syndrome always attracts attention. The tone of all muscle groups is lost, the patient falls, remaining conscious. If an injury is sustained during the attack, he cannot react to the pain or change his position. Intense emotion can provoke a series of seizures – cataplexic status lasting from 2-5 minutes to an hour.
Sometimes seizures end with sleep. Their frequency and duration vary significantly even in one patient. For example, remission may occur within a month, and with exacerbation, seizures develop several times a day. With a prolonged course of the disease, patients learn to build their behavior in such a way as to avoid provoking an attack of emotions.
The main complication of cataplexy is physical injuries caused by a sudden fall. The situation is aggravated by the fact that in the first minutes after the incident, a person cannot report pain and get help. There are many limitations in the life of patients. For example, they are forced to give up driving a car, since weakness in the muscles does not allow them to continue driving a vehicle and causes road accidents.
Seizures interfere with the performance of work duties that require constant concentration of attention. It is impossible to work on the production line, in conditions of increased danger. With frequent attacks that are difficult to treat, patients become socially maladapted – they lose their workplace, do not leave the house alone.
There are no specific instrumental examinations to confirm cataplexy. Diagnosis is carried out by clinical methods. The main examination is carried out by a neurologist, in addition, the participation of a psychiatrist, a somnologist may be required. Most often, patients are diagnosed with type 1 narcolepsy. 65-70% of people with this disease develop cataplexic seizures, which are described as states of muscle weakness that come after an irresistible drowsiness during the day.
The method of analyzing video recordings can be used. Classic cataplexy seizures have three phases:
- the first is characterized by closing the eyes, bending the knees;
- the second is the disappearance of a smile, lowering of the jaw, violation of posture;
- the third is atonic laying on the floor.
The isolation of these phases, consideration of provoking factors and concomitant disease is important when conducting differential diagnosis. Should be excluded:
- Conversion disorder. Individuals with hysterical neurosis may have conversion symptoms similar to a cataplexic attack. Distinctive features: the presence of a hysteroid character, the absence of narcolepsy and a direct connection of seizures with vivid emotions.
- Syncopal state. Syncope caused by a transient slowing of blood flow in the brain is characterized by a decrease in skeletal muscle tone. Differential signs: short–term loss of consciousness, pallor of the skin, duration – up to 20-30 seconds.
- Atonic absense. Paroxysmal changes in muscle tone with a fall occur with small epileptic seizures. Differences from cataplexy: the presence of an “aura”, unconsciousness, amnesia for the seizure that occurred (often). Atonic absences affect all the muscles of the body, but sometimes they are very short (the patient does not have time to fall).
Methods that can influence the cause of the syndrome are at the stage of experimental development. To date, pharmacotherapy is used in practice, which does not eliminate attacks of muscle atony forever, but provides long-term remission and complete relief of symptoms. The key goal of therapeutic and preventive measures is to improve the quality of life. Their basis is the use of the following medicines:
- SSRI. During the attack, eye movements characteristic of the rapid phase of sleep are noted. Selective serotonin reuptake inhibitors suppress “fast sleep”, reduce the frequency of atonic seizures.
- Tricyclic antidepressants. Drugs of this group can be prescribed instead of SSRIs. They also suppress the rem sleep phase, increase the duration of delta sleep. They act more intensively, but more often provoke side effects.
- Anticonvulsants. Anticonvulsants, commonly used for the treatment of epilepsy, prevent muscle paroxysms of cataplexy. When they are taken, states of muscle weakness occur less frequently, occur in a lighter form.
In case of sleep disorders, imidazopyridines, cyclopyrrolones, melatonin preparations are additionally prescribed. As a rule, it is necessary to adhere to medical prescriptions throughout life. In addition to medical treatment, patients are recommended to strictly observe sleep hygiene: sleep at least 8 hours at night and no more than 30 minutes during the day at the same time. Deprivation of night sleep, night shift work, stressful situations are contraindicated.
In the last ten years, the effectiveness of drugs capable of affecting the pathogenetic link of cataplexy has been actively investigated. Orexin (hypocretin) and neorexin drugs have been developed and continue to be tested. The latter group includes H3 antagonists (histamine receptor blockers) and monoaminergic reuptake blockers of various mediators.
The drug pitolisant (pitolisant) is a reverse agonist of H3 receptors. It was approved by the European Union in 2016 for the treatment of type I narcolepsy accompanied by cataplexy. Another 8 neorexin drugs are undergoing clinical trials. For example, JZP-110 blocks dopamine uptake and increases the level of daytime wakefulness. Treatment with orexin-based drugs, gene and immune therapy are at the stage of experimental development.
Prognosis and prevention
If the doctor’s prescriptions are followed, patients with cataplexy manage to achieve stable remission or decrease the severity of seizures. Preventive measures – maintaining the correct mode of wakefulness and sleep, increasing stress tolerance, avoiding situations that provoke intense emotions. It is necessary to refuse the use of psychostimulating substances, coffee, alcohol. To prevent another attack before an emotionally intense event, it is recommended to take sedatives.