Athetosis is a separate form of subcortical hyperkinesis characterized by involuntary slow movements in the distal extremities with a change in muscle tone. It can be an integral part of the clinic of perinatal, hypoxic, hereditary-degenerative brain lesions. Athetosis is diagnosed clinically, the underlying disease is clarified on the basis of a study of the neurological status, cerebral circulation, cerebral morphology, biochemical blood parameters. Neuroleptics, benzodiazepines, levodopa preparations, and cholinolytics are used in the treatment. In severe forms, stereotactic interventions are resorted to.
The term “athetosis” comes from the Greek word meaning “moving”. The name reflects the characteristic worm-like involuntary movements. In the literature on neurology, the synonymous name of the disease appears – athetoid hyperkinesis. Hyperkinesis refers to non-directional motor acts that occur against the will of the patient. Since athetosis is accompanied by slow movements without transition to tonic spasm, in the hyperkinesis group it occupies an intermediate position between chorea with its rapid motor acts and torsion dystonia, characterized by spastic stiffening in a certain pose. There are borderline forms that cannot be unambiguously differentiated, which are designated as choreoathetosis, athetoid dystonia. The disease occurs among children and adults, the prevalence does not depend on the gender of patients.
The etiofactors are hereditary and acquired lesions of subcortical ganglia. In adults, genetic and vascular causes predominate, in children – perinatal damage to the central nervous system. Among the main factors are:
- Hereditary diseases. Athetosis is typical for Wilson’s disease, Lesh-Nihan syndrome, Machado-Joseph disease, Huntington’s disease.
- Disorders of cerebral circulation. Acute and chronic cerebral ischemia causes hypoxic damage, including those included in the extrapyramidal system of basal nuclei.
- Birth trauma of a newborn. Complicated childbirth, narrow pelvis, pathological course of the period of expulsion of natural childbirth can cause intracranial birth trauma, intranatal asphyxia with damage to extrapyramidal structures.
- Fetal hypoxia. Oxygen starvation can be provoked by fetoplacental insufficiency, intrauterine infections, hemolytic disease. The cerebral structures responsible for the regulation of the motor sphere are more sensitive to hypoxia. Athetosis of hypoxic genesis is included in the clinical picture of cerebral palsy.
- Prematurity. The occurrence of disorders in the motor sphere is associated with the underdevelopment of the corresponding cerebral structures.
- Encephalitis. Athetosis against the background of inflammatory brain damage is noted mainly in children. Among adults, it is observed with a rare form of infectious encephalopathy – Creutzfeldt-Jakob disease.
In rare cases, athetosis is provoked by intoxication, traumatic brain injury, brain tumor, dysmetabolic, autoimmune processes in the body.
As a result of exposure to these factors, disorders occur in the extrapyramidal system that distributes the tone, duration and strength of contractions between different muscle groups. The exact pathogenesis has not been established. The presumed localization of pathological changes is caudate and lenticular subcortical nuclei. The consequence of extrapyramidal dysfunction is excessive uncoordinated stimulating impulses going to the muscles along the nerve trunks. Under the influence of nerve impulses, alternate muscle contractions occur, externally expressed by violent motor acts. At the same time, it remains unknown what causes the occurrence of the athetoid form of hyperkinesis.
Depending on the localization and nature of movements , several clinical forms of pathology are distinguished:
- Hemiatetosis is a unilateral athetosis covering the muscles of one half of the body and face. It can be left- and right-sided.
- Generalized athetosis is bilateral athetoid movements that spread to all muscles. Typical difficulty of speech function.
- Choreoathetosis is a hyperkinetic syndrome that combines the signs of athetosis and chorea. Athetosis-specific movements have a high speed characteristic of chorea.
- Athetoid dystonia – typical hyperkinesis is periodically combined with an elongation of the phase of tonic muscle contraction, expressed in the fixation of the pose.
The basis of clinical symptoms is a gradual slow change in the tone of various muscle groups, externally manifested by chaotic crawling motor acts. Movements arise spontaneously, are beyond the conscious control of the patient. Athetosis is provoked and intensified with purposeful actions, psychoemotional stress, regresses at rest, disappears during sleep. Patients indicate a certain position (often lying on their stomach), which allows them to reduce movement.
Typically, the involvement of the distal parts of the extremities (fingers, hands, feet), tongue. In more severe cases, athetosis spreads to the proximal parts, cervical and facial muscles. Forcible movements of the fingers are characterized as worm-like, in the proximal parts of the limbs the movements are serpentine, the defeat of the mimic muscles leads to grimacing. There is no fixation of the resulting finger/limb placement, pretentious poses smoothly transform into each other. Against the background of athetosis, voluntary motor acts are difficult, in severe cases self-service is impossible. Involvement of the muscles of the face and neck leads to a speech disorder (athetoid dysarthria).
Usually athetosis is an integral part of the underlying disease, combined with typical symptoms for it. Athetoid hyperkinesis in the framework of hereditary pathology, severe perinatal damage occurs against the background of intellectual decline (progressive dementia, mental retardation). A separate nosology is a double form of the disease, manifesting in children at 11-12 months with previous muscular hypotension. It is characterized by bilateral athetosis, choreoathetosis with spread to the orofascial muscles, trunk, neck. Occurs with swallowing disorder, dysarthria. In most cases, intellectual abilities are preserved.
Athetoid hyperkinesis is diagnosed during the examination of the patient. Further studies are necessary to establish the etiology and diagnosis of the underlying disease. The following diagnostic measures are carried out:
- Anamnesis collection. The time of the onset of hyperkinesis, its nature, development, the presence of perinatal pathology (in children), hereditary burden are taken into account.
- Neurologist’s examination. It is aimed at differentiation from pseudoathetosis, identification of symptoms indicating a specific underlying pathology.
- Brain MRI. Visualizes organic changes, ischemic zones, tumors, foci of inflammation, degenerative processes. In 60% of cases, double athetosis is accompanied by the presence of hyperintensive foci in the area of the shell and the anterior nuclei of the thalamus.
- Investigation of cerebral blood flow. It is carried out if vascular etiology is suspected. It is carried out by duplex scanning, ultrasound, MRI of cerebral vessels.
- Blood test. Allows you to detect dysmetabolic processes characteristic of hereditary diseases: a decrease in blood ceruloplasmin, an increase in the concentration of uric acid, copper in the urine.
It is necessary to differentiate athetosis from pseudoathetosis, minor chorea, torsion dystonia. Pseudoathetous manifestations are the result of damage to the conductive tracts of deep sensitivity. Pseudoathetosis occurs without musculotonic disorders, occurs with the loss of visual control over the action, is observed together with sensitive disorders. Minor chorea is characterized by the paroxysmal nature of hyperkinesis, the debut at the age of ten. Torsion dystonia is accompanied by the formation of pathological twisting poses with fixation in them.
Therapy is aimed at relieving the underlying pathology. Specific drugs for the treatment of athetosis have not been developed. Some effect of the use of cholinolytics, dopamine metabolism regulators (levodopa), neuroleptics, benzodiazepine anticonvulsants was noted. Periodic courses of taking pyridoxine, physical therapy are recommended. According to indications, glutamic acid is used to stimulate intellectual development.
Severe athetosis may be an indication for stereotactic surgery – the destruction of the ventrolateral nucleus of the thalamus, which provides the connection of extrapyramidal formations. Surgical intervention can reduce the severity of hyperkinesis, but it is dangerous for the development of pseudobulbar syndrome, with double athetosis it aggravates swallowing disorders. The experimental method of treatment is deep brain stimulation, which is an inhibitory effect on extrapyramidal structures.
Prognosis and prevention
The outcome depends on the underlying pathology. Patients who became ill in childhood, despite severe motor disorders, can live to a very old age. A serious prognosis has a hereditarily conditioned athetoid hyperkinesis, occurring with progressive degenerative changes in the central nervous system. Double athetosis is characterized by a stable course, with age partial compensation of motor disorders is possible. Prevention includes measures to prevent provoking factors: adequate management of pregnancy and childbirth, timely treatment of disorders of cerebral hemodynamics, neuroinfections.