Dystonia
Dystonia is a movement disorder characterized by persistent or irregular muscle contractions that cause abnormal, usually repetitive, movements and/or abnormal postures that interfere with certain actions in the involved areas of the body.
Dystonic movements are usually uniform and rotational in nature, and may also be manifested by tremor. Dystonia usually manifests or intensifies with voluntary movements and is accompanied by excessive muscle activation.
Distribution of affected body areas:
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Focal. Only one area of the body is involved (blepharospasm, oromandibular dystonia, cervical dystonia, laryngeal dystonia, and writer's cramp). Cervical dystonia is considered a form of focal dystonia, despite the fact that not only the neck but also the shoulder may participate in the formation of this pathology.
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Multifocal. Two or more non-adjacent areas of the body are affected (dystonia of the upper and lower limbs, cranial and lower limbs).
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Generalized. The trunk and at least 2 other areas are involved. The generalized form with involvement of the legs is considered separately from the form of dystonia in which the legs are not involved.
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Hemidystonia. Several areas of the body on one side are affected. Usually secondary to contralateral brain damage.
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Segmental. Two or more adjacent areas of the body are affected (cranial dystonia, bibrachial dystonia).
Diagnostics
The algorithm for diagnosing dystonia consists of the following stages:
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Clinical assessment - detection of dystonia syndrome and assessment of its clinical characteristics;
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Documentation of clinical manifestations - video and photo recording, assessment of clinical manifestations using standard assessment scales for each clinical form of dystonia;
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Genetic testing - if there is a suspicion of a hereditary nature of primary dystonia, when planning deep brain stimulation for patients with segmental and generalized dystonia;
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Instrumental diagnostics - to exclude brain damage and other diseases if there is a suspicion of a secondary nature of dystonia, to identify the pattern of muscle activation and in some specific cases;
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Diagnostic test with L-DOPA - if there is a suspicion of DOPA-dependent forms of dystonia.
Motor manifestations associated with dystonia:
| Dystonic tremor |
Spontaneous pulsating, rhythmic, but often inconstant, patterned movements that occur when the muscles affected by dystonia contract, often intensifying when attempting to maintain the original (normal) posture. Dystonic tremor may not be relieved even if the pathological dystonic posture is allowed to develop without resistance (“zero point”). Dystonic tremor can sometimes be quite difficult to distinguish from essential tremor. |
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| Excessive movement |
Excessive motor activation, often seen in dystonia, is involuntary muscle contractions that accompany but are anatomically distinct from the primary dystonic movements. They typically occur at the peak of the dystonic movements. |
| Mirror movements |
Mirror dystonia is a specific posture or movement pattern that is similar or identical in nature to dystonic movements and usually occurs on the affected side when movements or actions are performed on the contralateral side. |
| Corrective gestures (sensory actions or antagonistic movements) |
Voluntary actions that allow a special way to eliminate the occurrence of a pathological posture or to correct dystonic movements. Usually these are simple movements or touches in the area of the body affected by dystonia, but at the same time they are not an intensive counteraction to the manifestations of dystonia. |
Treatment of dystonia
Local injections of botulinum toxin type A (BTA) into target muscles are the first-line treatment for most forms of focal dystonia. This method eliminates abnormal muscle contractions while maintaining their function. To achieve stable remission and maintain the quality of life of patients, BTA drugs should be prescribed to the patient immediately after diagnosis of focal dystonia, since they are first-line treatment drugs. Injections should be administered regularly, on average, every 3-4 months. However, the interval between injections may vary depending on the patient's well-being and can be reduced to 2 months or increased. Modern European guidelines for the treatment of dystonia welcome the tactics of a flexible interval between injections, "at the patient's request", when the effect of the previous injection decreases. The safety and high efficiency of botulinum therapy have been proven by numerous controlled studies and 30 years of clinical practice.
Surgical treatment methods include deep brain stimulation (DBS – Deep Brain Stimulation, neuromodulation), which has replaced stereotactic destruction, as well as peripheral surgeries (cervical radicotomy, accessory nerve decompression, selective denervation and rhizotomy, myectomy). Deep brain stimulation is performed in cases of persistent resistance to botulinum therapy (lack of effect from 5-6 botulinum therapy procedures in a sufficient dose and with the correct selection of muscles for injection, confirmed by electromyographic examination), as well as in case of generalization of dystonia. Peripheral surgeries are of limited use. An additional method of treating blepharospasm is blepharoplasty surgery to remove excess skin and soft tissues of the upper eyelid, which improves the tolerability and results of botulinum therapy. In patients with hemifacial spasm, if neurovascular compression of the 7th nerve root is identified in the etiology, neurovascular decompression surgery is performed.