Definition and Overview
Dystonia is a movement disorder syndrome in which persistent or intermittent muscle contractions cause abnormal postures, twisting movements, or repetitive movements. These contractions are involuntary and are often triggered or made worse by certain movements or postures.
Dystonia is classified into focal, segmental, hemidystonia, and generalized depending on the extent of involvement. Also, depending on the cause, it is divided into primary (independent neurodegeneration) and secondary (due to drugs, brain lesions, metabolic diseases, etc.).
Causes and Pathophysiology
The pathophysiology of dystonia is due to dysfunction of the motor control circuit including the basal ganglia, especially the striatum and globus pallidus. It is known that loss of inhibition causes excessive motor pattern activation.
Important genetic causes include DYT1 (TOR1A gene mutation, childhood generalized dystonia) and DYT11 (dopamine-responsive dystonia, GCH1 mutation). Secondary causes include stroke, brain tumor, cerebral palsy, dopamine blocking drugs (antipsychotic drugs), and Wilson's disease.
symptoms
The clinical manifestations of dystonia vary depending on the area involved.
Cervical dystonia (torticollis): This is the most common focal dystonia. Involuntary contraction of the neck muscles causes the head to rotate (torticollis), lateral tilt (laterocollis), forward bend (anterocollis), or retrocollis, and is often accompanied by pain.
Blepharospasm: A symptom in which both eyelids are forced to close due to involuntary contraction of the orbicularis oculi. It is worsened by bright light, fatigue, and stress.
Writer's cramp: This is hand dystonia that occurs only when performing specific tasks such as writing.
Oromandibular dystonia: Involuntary contraction of the mouth, jaw, and tongue muscles causes chewing, speaking, and swallowing difficulties.
Generalized dystonia: It often develops in childhood and can gradually progress throughout the body, resulting in gait disturbance and severe functional decline.
Symptoms are characterized by a temporary decrease due to certain postures (sensory trick, geste antagoniste).
diagnosis
Diagnosis is made clinically. Classify the type and cause of dystonia through medical history (age of onset, progression pattern, family history, medication history) and neurological examination.
Tests to rule out secondary causes: - Blood tests: copper (Wilson's disease), thyroid, metabolic abnormality tests - Brain MRI: Confirmation of structural abnormalities such as basal ganglia and thalamus - Genetic testing: DYT1 (TOR1A), DYT11 (GCH1), etc. in case of clinical suspicion - Levodopa response test: Differentiating dopamine-responsive dystonia
treatment
Botulinum toxin injection
It is the first-line treatment for focal dystonia. Botulinum toxin type A or B is injected into the relevant muscle to block muscle hyperactivity. It is widely applied to cervical dystonia, eyelid spasms, and oromandibular dystonia. In clinical studies, symptom improvement was reported in approximately 60-90% of patients. The effect lasts about 3 to 4 months and requires repeated injections.
medication
- 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 adjunct to relieve muscle tension.
- Tetrabenazine: A dopamine-depleting drug used in some secondary dystonias.
deep brain stimulation
Deep brain stimulation (DBS) of the globus pallidus interna (GPi) is effective in patients with generalized dystonia, especially DYT1 gene mutation. In a clinical study, it was reported that the functional disability scale (Burke-Fahn-Marsden score) significantly improved after GPi-DBS.
prognosis
Focal dystonia can be controlled with appropriate treatment and is mostly non-progressive. Generalized dystonia has a high risk of progressing to the entire body if it starts in childhood, especially in the lower extremities. Early diagnosis, genetic testing, and appropriate treatment selection are important to maintain function.
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This information is provided for medical educational purposes and is not a substitute for individual medical care or treatment. If you have any symptoms, be sure to seek professional advice. Inquiries: Osang Neurosurgery 1599-5453 | osns.co.kr