Definition and Overview
Dystonia is a movement disorder syndrome characterized by sustained or intermittent muscle contractions causing abnormal postures, twisting movements, or repetitive motions. These contractions are involuntary and are often triggered or worsened by specific actions or postures.
Dystonia is classified by the extent of body involvement as focal, segmental, hemidystonia, or generalized. It is also divided by etiology into primary (independent neurodegeneration) and secondary (caused by medications, brain lesions, metabolic disorders, etc.).
Etiology and Pathophysiology
The pathophysiology of dystonia is attributed to dysfunction of motor control circuits involving the basal ganglia, particularly the striatum and globus pallidus. Loss of normal inhibitory function is known to cause excessive activation of motor patterns.
Important genetic causes include DYT1 (TOR1A gene mutation, childhood-onset generalized dystonia) and DYT11 (dopa-responsive dystonia, GCH1 mutation). Secondary causes include stroke, brain tumors, cerebral palsy, dopamine-blocking medications (antipsychotics), and Wilson's disease.
Symptoms
The clinical presentation of dystonia varies depending on the body region involved.
Cervical dystonia (torticollis): The most common focal dystonia. Involuntary contraction of neck muscles causes the head to rotate (torticollis), tilt laterally (laterocollis), flex forward (anterocollis), or extend backward (retrocollis), often accompanied by pain.
Blepharospasm: Involuntary contraction of the orbicularis oculi muscle causing forced bilateral eyelid closure. It is worsened by bright light, fatigue, and stress.
Writer's cramp: Hand dystonia that occurs only during specific task performance such as writing.
Oromandibular dystonia: Involuntary contraction of the mouth, jaw, and tongue muscles causing difficulties with chewing, speaking, and swallowing.
Generalized dystonia: Often presents in childhood and may progressively spread to the entire body, causing gait disturbance and severe functional impairment.
A characteristic feature is that symptoms can be temporarily reduced by specific postures or sensory tricks (geste antagoniste).
Diagnosis
Diagnosis is made clinically. The type and cause of dystonia are classified through medical history (age of onset, progression pattern, family history, medication history) and neurological examination.
Tests to exclude secondary causes:
- Blood tests: Copper (Wilson's disease), thyroid, and metabolic studies
- Brain MRI: To identify structural abnormalities in the basal ganglia, thalamus, etc.
- Genetic testing: DYT1 (TOR1A), DYT11 (GCH1), etc. when clinically suspected
- Levodopa trial: To differentiate dopa-responsive dystonia
Treatment
Botulinum Toxin Injection
This is the first-line treatment for focal dystonia. Botulinum toxin type A or B is injected into the affected muscles to block muscle overactivity. It is widely applied to cervical dystonia, blepharospasm, oromandibular dystonia, and other forms. Clinical studies have reported symptom improvement in approximately 60-90% of patients [1]. The effect lasts approximately 3-4 months, requiring repeated injections.
Pharmacological Treatment
- Anticholinergics: Trihexyphenidyl is used for generalized and segmental dystonia and may be particularly effective in children.
- Baclofen: Can be administered orally or intrathecally.
- Clonazepam: Used as an adjunctive treatment for muscle relaxation.
- Tetrabenazine: A dopamine-depleting agent used in some secondary dystonias.
Deep Brain Stimulation
Deep brain stimulation (DBS) targeting the globus pallidus interna (GPi) is effective for generalized dystonia, particularly in patients with DYT1 gene mutations. Clinical studies have reported significant improvement in the Burke-Fahn-Marsden disability score following GPi-DBS [2].
Prognosis
Focal dystonia can be managed with appropriate treatment and is mostly non-progressive. Generalized dystonia, particularly when onset occurs in childhood and begins in the lower extremities, carries a high risk of progression to the entire body. Early diagnosis, genetic testing, and appropriate treatment selection are important for maintaining function [3][4].
---
This information is provided for medical educational purposes only and does not replace professional medical advice.
If you are experiencing symptoms, please consult a specialist.
Contact: OSANG Neurosurgery 1599-5453 | osns.co.kr