Muscular dystonia is a syndrome of central nervous system damage, manifested by inconsistent arrhythmic changes in the tone of various muscle groups. Clinically characterized by focal or generalized involuntary fixed postures or motor acts. Diagnosis is carried out according to clinical data on the presence of dystonic phenomena. Instrumental examinations (MRI, ENMG) are aimed at finding the causal disease. Conservative therapy includes kinesiotherapy, prescription of pharmaceuticals, local administration of botulinum toxin, physiotherapeutic effects. With generalized forms, neurosurgical treatment is possible.
ICD 10
G24 Dystonia
General information
Muscle tension (tone) is necessary to maintain body posture, exercise movements. In contrast to reduced (hypotension) and increased (hypertonus) muscle tension, muscular dystonia (MD) denotes a violation of the adequate ratio of the tone of individual muscles or muscle groups. MD is not a nosological unit, it is a syndrome that occurs with various lesions of the central nervous system. According to European studies, muscular dystonia occurs in Western European countries with a frequency of 11.2 cases per 100 thousand population. The onset of manifestations is possible at any age. An earlier onset of symptoms leads to a faster progression of the syndrome with subsequent generalization of the process.
Causes
Various brain lesions that spread to the structures responsible for regulating the tone of the extrapyramidal system can act as etiofactors of MD. In children of the first year of life, muscular dystonia develops mainly due to disorders of the development of the nervous system in the prenatal period or its damage during childbirth. Possible causes include fetal hypoxia, intrauterine infections, toxic effects (smoking, alcohol intake, drug addiction, drug treatment of a pregnant woman), birth trauma of a newborn. In older children and adults , the following main etiological factors are distinguished:
- Genetic changes. Gene mutations cause changes in the mediator or receptor part of nerve synapses involved in the transmission of tone-regulating effects. Hereditary forms of MD include idiopathic blepharospasm, myoclonic dystonia, primary torsion dystonia.
- Traumatic brain injury. Damage to subcortical structures in TBI, conducting tracts of the extrapyramidal system causes a disorder of the central regulation of muscle tone. With incomplete recovery, muscular dystonia persists in the post-traumatic period.
- Brain tumor. Sprouting cerebral tissues, aggressive intracerebral neoplasia destroys neurons and pathways. With noninvasive growth, as the size of the tumor increases, compression of the surrounding formations occurs. MD occurs when extrapyramidal structures are involved in the pathological process.
- Encephalitis. Inflammatory damage of various levels of the extrapyramidal system in encephalitis entails a disorder of its regulatory effect on muscle tone. MD can manifest itself against the background of the subsiding of the acute inflammatory process and the regression of more severe neurological symptoms.
- Medical effects. Antiparkinsonian pharmaceuticals, neuroleptics, antidepressants, antipsychotics can provoke dystonic disorders. Risk factors for side effects of therapy are long duration of administration and high dosages.
Pathogenesis
The above-mentioned etiofactors cause dysfunction of the multilevel system of regulation of muscle tension. As a result, spontaneous impulses occur, excessively activating certain muscles. The activated muscle group enters a state of tonic contraction, which leads to violent movement followed by hardening. Depending on the localization of the muscle group subject to pathological impulses, an involuntary turn of the head, torso twisting, eye closing, dystonic trism, etc., is possible. Alternation of excessive tension of antagonist muscles is the basis of hyperkinesis – involuntary motor acts of different amplitude and speed. The pathogenetic mechanism of the development of many MD continues to be studied.
Classification
According to the localization of dystonic phenomena, cranial, paraorbital, oromandibular, cervical, pharyngeal, torsion and other forms of MD are distinguished. According to the etiology, dystonic syndrome is classified into primary (hereditary, idiopathic), secondary (acquired). The following classification is based on the prevalence of the pathological process in muscle groups. In accordance with this criterion , the following forms of MD are distinguished:
- Focal. The pathological process covers no more than one muscle group. Focal forms include writing spasm, blepharospasm, spastic dysphonia.
- Segmental. The tonic contraction extends to several adjacent muscle groups. An example is the combined oromandibular MD.
- Multifocal. Focal dystonic phenomena are observed in several parts of the body. Pathological muscle contractions in them can occur simultaneously and independently of each other.
- Generalized. Involuntary muscle tension extends to almost the entire skeletal musculature. Starting with focal forms, MD is able to transform into a generalized form.
As the dystonic syndrome develops, the severity of pathological changes worsens. In this regard, there are 4 degrees of MD severity. In clinical practice, they are evaluated as stages of dystonia development.
- I — changes are expressed minimally. Dystonic syndrome manifests itself in a situation of increased mental stress, with overwork.
- II — muscular dystonia occurs regularly during physical activity. There are no dystonic phenomena at rest.
- III — muscular dystonia is permanent, it increases with arbitrary movements. Difficulties are noted when performing actions involving dystonia-prone muscle groups. There are restrictions in professional activity.
- IV — pronounced MD, depriving the patient of the ability to perform individual movements independently. Invalidizes the patient.
Symptoms
The main clinical manifestations: dystonic postures and motor acts. Polymorphism of symptoms is caused by different localization of the process, strength, speed and frequency of muscle contractions. A common pattern for dystonic phenomena is their stereotypical nature, the occurrence in the process of performing arbitrary motor acts, increased fatigue, sleep deprivation, stress, reduction after sleep, rest, in a hypnotic state.
In most cases, muscular dystonia manifests in focal forms. Writing spasm is manifested by spastic contraction of the muscles of the hand, which makes it impossible to continue writing the text. Idiopathic blepharospasm is characterized by a contraction of the circular muscle of the eye, leading to squinting. The oromandibular form has several variants: trism, forcible opening of the mouth, stretching of the lips, sticking out of the tongue. Cervical MD is characterized by a violent turn, a tilt of the head, pharyngeal — a violation of swallowing, torsion — twisting torso turns. Adapting to dystonic seizures, patients develop habitual corrective gestures and movements that reduce the severity of muscle disorders.
In infants, muscular dystonia is manifested by unnatural poses, always turning the head in one direction, turning over only one side, lagging in static-motor development. In many cases, focal manifestations gradually transform into segmental ones, spread to other parts of the body, and after a few years pass into generalized MD. The earlier the debut of dystonia occurred, the faster generalization occurs. Long-term isolated course of focal dystonia is observed in patients with manifestation of clinical symptoms after 25-35 years.
Complications
Progressive muscular dystonia significantly disrupts the patient’s motor sphere, complicates professional and everyday activities. Over time, the performance of professional duties becomes impossible, the patient goes on disability. The cervical form is complicated by the development of torticollis. With torsion MD, curvature of the spine develops, respiratory disorders are possible in the later stages. Blepharospasm leads to entropion, dryness of the anterior segment of the eye. In some cases, the occurrence of neuritis and compression neuropathies of the peripheral nerves of the limb performing corrective dystonia movements is noted.
Diagnostics
The diagnosis is established by a neurologist on the basis of clinical data, taking into account complaints of dystonic manifestations and the results of the examination. Further diagnostic examinations are aimed at determining the cause of the dystonic syndrome, verification of the underlying disease. The main stages of diagnosis are:
- Collecting anamnesis. Diagnostic significance is the age of the onset of symptoms, the sequence of its development. In younger children, attention is paid to the perinatal anamnesis, in older patients — to the medications taken. Within the family history, the presence of diseases with dystonic manifestations in the closest relatives is established. If the hereditary nature of MD is suspected, a geneticist’s consultation is appointed, a genealogical analysis is carried out.
- Neurologist’s examination. In the neurological status, a focal or generalized violation of tone is determined. Muscle strength is preserved or slightly reduced. Reflex and sensitive areas without pathology may be impaired with the development of secondary neuropathies.
- Instrumental research. Conducted in order to identify organic pathology of the nervous system. In accordance with the symptoms, spine x-ray, MRI of one part of the spine, ultrasound of the head and neck, MRI of the brain, electroneuromyography, ultrasound of the nerve can be prescribed. Blepharospasm is an indication for an ophthalmologist’s consultation. If all possible organic diseases are excluded, the diagnosis of idiopathic MD is established.
Differential diagnosis is performed with amyotrophic lateral sclerosis, neuroacanthocytosis, Machado-Joseph disease. A distinctive feature of MD is the presence of a corrective gesture, which is absent in other extrapyramidal disorders. The absence of muscular atrophy makes it possible to distinguish dystonic syndrome from motor neuron disease. Neuroacanthocytosis is characterized by the presence of neurotic disorders, the detection of altered erythrocytes (acanthocytes) in the blood test.
Treatment
Therapy is aimed at reducing symptoms, improving the patient’s well-being. Its component is the exclusion of factors aggravating dystonia (overwork, excessive muscle tension, insufficient sleep, stressful situations). In order to achieve the best result in treatment, a combination of several of the following techniques are used:
- Kinesiotherapy. It is carried out by specialists of restorative medicine: a rehabilitologist, a kinesiotherapist, a masseur. Patients are recommended both passive techniques (massage, mechanotherapy), and active classes with specially selected corrective gymnastics, swimming in the pool.
- Medical treatment. The basic drugs are benzodiazepines that reduce neuronal excitability. Their combinations with muscle relaxants, sedatives, and antidepressants are possible. The positive therapeutic effect of cholinolytics is due to their ability to slow down the passage of a nerve impulse.
- Botulinum therapy. It is used for focal and segmental forms. Botulinum neurotoxin is injected directly into the muscles involved in pathological phenomena. Botulinum toxin blocks cholinergic transmission in the innervating muscle endings. The effect of the drug lasts up to 1 month.
- Physical therapy. The positive effect is provided by hydrotherapy, the use of therapeutic mud. In combination with general pharmacotherapy, electrophoresis of drugs, local magnetotherapy, and ultrasound treatment are prescribed.
Surgical treatment is indicated for severe generalized MD against the background of insufficient effectiveness of conservative methods. Stereotactic destruction of the ventrolateral thalamic nucleus is most often used. Methods of surgical treatment of various forms of the disease continue to be developed.
Prognosis and prevention
The course of secondary dystonic syndrome depends on the nature of the underlying disease. The prognosis of idiopathic forms is more serious the earlier the manifestation of clinical manifestations occurred. Complex therapy started in a timely manner can significantly improve the quality of life of the patient, delay disability. Prevention consists in the exclusion of adverse effects on the fetus during intrauterine development, an adequate choice of delivery method, prevention of injuries, infectious and oncological lesions of the central nervous system, careful planning of timing and dosages during drug therapy.
