Definition
Athetosis is a separate form of subcortical hyperkinesis characterized by involuntary slow movements in the distal limbs with changes in muscle tone. It may be a part of the clinic of perinatal, hypoxic, hereditary-degenerative brain lesions. Athetosis is diagnosed clinically, and the underlying disease is clarified based on the study of neurologic status, cerebral circulation, cerebral morphology, and biochemical blood parameters. In treatment, neuroleptics, benzodiazepines, levodopa preparations, and cholinolytics are used. In severe forms, stereotactic interventions are resorted to.
General information
The term “athetosis” comes from the greek word meaning “moving.” The name reflects the characteristic worm-like involuntary movements. In the literature on neurology, a synonymous name for the disease appears – athetoid hyperkinesis. Hyperkineses are defined as non-targeted motor acts occurring beyond the patient’s will. Since athetosis is accompanied by slow movements without transition to tonic spasm, in the group of hyperkineses, it occupies an intermediate position between chorea with its rapid motor acts and torsion dystonia, characterized by spastic freezing in a particular position. There are borderline forms that cannot be unambiguously differentiated and are referred to as choreoathetosis or athetoid dystonia. The disease occurs in children and adults, and its prevalence does not depend on the sex of patients.
Causes of athetosis
The etiologic factors are hereditary and acquired lesions of the subcortical ganglia. In adults, genetic and vascular causes predominate; in children – perinatal CNS damage. Following main factors are distinguished:
- Hereditary diseases. Athetosis is typical for Wilson’s disease, Lesch-Nyhan syndrome, Machado-Joseph disease, and Huntington’s disease.
- Cerebral circulatory disorders. Acute and chronic cerebral ischemia causes hypoxic damage, including basal nuclei of the extrapyramidal system.
- Birth trauma of the newborn. Complicated labor, narrow pelvis, and pathological course of the expulsion period of natural childbirth can cause intracranial birth trauma and intrapartum asphyxia with lesions of extrapyramidal structures.
- Fetal hypoxia. Oxygen deprivation can be provoked by fetoplacental insufficiency, intrauterine infections, and hemolytic disease. The cerebral structures responsible for regulating the motor sphere are more sensitive to hypoxia. Hypoxic athetosis is part of the clinical picture of infantile cerebral palsy.
- Prematurity. The emergence of disorders in the motor sphere is associated with 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 in a rare form of infectious encephalopathy – Creutzfeldt-Jakob disease.
In rare cases, athetosis is provoked by intoxication, brain injury, brain tumor, dysmetabolic, or autoimmune processes in the body.
Pathogenesis
As a result of etiologic factors, there are disturbances in the extrapyramidal system, which distributes the tone, duration, and strength of contractions between different muscle groups. The exact pathogenesis has yet to be established. The presumed localization of pathological changes is the caudate and lenticular subcortical nuclei. Extrapyramidal dysfunction results in excessive uncoordinated stimulating impulses to the muscles along the nerve trunks. Under the influence of nerve impulses, alternating muscle contractions are outwardly expressed by violent motor acts. It remains unknown what causes the athetoid form of hyperkinesis.
Classification
Depending on the localization and character of movements, several clinical forms of pathology are distinguished:
- Hemiathetosis – unilateral athetosis involving muscles of one half of the body and face. It can be left- or right-sided.
- Generalized athetosis – bilateral athetoid movements spreading to all muscles. Difficulty in speech function is typical.
- Choreoathetosis is a hyperkinetic syndrome that combines features of athetosis and chorea. The movements specific to athetosis have a high-speed characteristic of chorea.
- Athetoid dystonia – typical hyperkinesis periodically combined with prolongation of the phase of tonic muscle contraction, expressed in posture fixation.
Symptoms of athetosis
Clinical symptomatology is based on a gradual, slow change in the tone of various muscle groups, outwardly manifested by chaotic creeping motor acts. The movements occur spontaneously and are beyond the patient’s conscious control. Athetosis is provoked and intensified with purposeful actions and psycho-emotional tension, regresses at rest, and disappears during sleep. Patients indicate a particular posture (often lying on the stomach), allowing them to reduce movements.
Typical involvement of distal limbs (fingers, hands, feet), tongue. In more severe cases, athetosis extends to the proximal parts, neck and mimic muscles. Violent movements of the fingers are characterized as worm-like; in the proximal parts of the limbs, the movements are serpentine, and the lesion of the mimic muscles leads to grimacing. Fixation of the resulting finger/limb stance is absent; flamboyant postures smoothly transform into each other. Voluntary motor acts are difficult against the background of athetosis; in pronounced cases, self-care is impossible. Involvement of the muscles of the face and neck leads to a speech disorder (athetoid dysarthria).
Usually, athetosis is a component of the underlying disease, combined with typical symptoms for it. Athetoid hyperkinesis within 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 muscle hypotonia. It is characterized by bilateral athetosis, choreoathetosis with spread to orofacial muscles, trunk, neck. It proceeds with swallowing disorder and dysarthria. In most cases, intellectual abilities are preserved.
Diagnosis
Athetoid hyperkinesis is diagnosed during patient examination. Further investigations are necessary to establish the etiology and diagnosis of the underlying disease. The following diagnostic measures are performed:
- Collection of anamnesis. The time of hyperkinesis’s debut, its nature, development, the presence of perinatal pathology (in children), and hereditary aggravation are considered.
- A neurologist examines the patient. The examination aims to differentiate from pseudoathetosis and identify symptoms indicative of a specific underlying pathology.
- MRI of the brain. Visualizes organic changes, areas of ischemia, tumors, foci of inflammation, and degenerative processes. In 60% of cases, double athetosis is accompanied by hyperintense foci in the shell region and anterior thalamic nuclei.
- Examination of cerebral blood flow is carried out when a vascular etiology is suspected. It is carried out by duplex scanning, ultrasound, and MRI of cerebral vessels.
- Blood biochemical analysis allows you to detect dysmetabolic processes characteristic of hereditary diseases, such as decreased blood ceruloplasmin and increased uric acid and copper in the urine.
Athetosis should be differentiated from pseudoathetosis, pseudo-athetosis, pseudo-chorea, and torsion dystonia. Pseudoathetosis manifestations result from lesions of the conductive tracts of deep sensitivity. Pseudoathetosis occurs without muscle-tonic disorders, with loss of visual control over the action, and is observed together with sensory disorders. Minor chorea is characterized by an attack-like character of hyperkinesis, debuting at ten. Torsion dystonia is accompanied by the formation of pathological twisting postures with fixation in them.
Treatment of athetosis
Therapy aims to manage the underlying pathology. Specific drugs for the treatment of athetosis have not been developed. Some effects of using cholinolytics, regulators of dopamine metabolism (levodopa), neuroleptics, and benzodiazepine anticonvulsants have been noted. Periodic courses of pyridoxine intake and therapeutic exercise are recommended. When indicated, 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 communication of extrapyramidal formations. Surgical intervention can reduce the severity of hyperkinesis but is dangerous with the development of pseudobulbar syndrome, in which double athetosis aggravates swallowing disorders. An experimental treatment method is deep brain stimulation, which has an inhibitory effect on extrapyramidal structures.
Prognosis and prevention
The outcome depends on the underlying pathology. Despite pronounced movement disorders, patients affected in childhood may live to a ripe old age. Hereditary athetoid hyperkinesis with progressive degenerative changes in the CNS has a severe prognosis. A stable course characterizes double athetosis; partial compensation of movement disorders is possible with age. Prevention includes measures to prevent provoking factors: adequate management of pregnancy and childbirth, timely treatment of cerebral hemodynamic disorders, and neuro infections.