Dystonia
Dystonia is a movement disorder of sustained or intermittent muscle contractions causing repetitive, directional twisting postures; adult-onset focal forms (cervical dystonia, blepharospasm) are treated with botulinum toxin injection, while young-onset or progressive cases warrant a levodopa trial and screening for Wilson disease.
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What this article covers
- Overview
Definition: dystonia is a movement disorder defined by sustained or intermittent muscle contractions that produce repetitive, patterned, and directional twisting movements or abnormal fixed postures of one or more body parts.
- Epidemiology
Bimodal age distribution: generalized dystonias predominantly begin before age 25 years, while focal adult-onset dystonias (cervical dystonia, blepharospasm, spasmodic dysphonia, writer's cramp) present in middle adulthood.
- Risk factors
Genetic mutation: autosomal dominant forms (DYT1, DYT6, ATP1A3), autosomal recessive forms (including Wilson disease), X-linked forms (Lesch-Nyhan syndrome), and mitochondrial disease (Leigh…
- Pathophysiology
Basal ganglia network dysfunction: dystonia arises from abnormal basal ganglia-thalamocortical motor circuits, producing loss of the normal reciprocal inhibition between agonist and antagonist…
- Clinical features
Directional, patterned posturing: the hallmark finding is a sustained, repetitive twisting or fixed abnormal posture that is stereotyped from episode to episode in the same patient, unlike the random flowing movements of chorea.
- Differential diagnosis
Parkinson disease: dystonia can be an associated feature, but the core diagnosis requires bradykinesia and rest tremor.
- Diagnosis
Establishing basis: the diagnosis of dystonia is made clinically, by recognizing the sustained, directional, stereotyped contraction pattern on examination together with its anatomic distribution and…
- Management
First, treat an acute drug-induced dystonic reaction emergently: give diphenhydramine 25 to 50 mg IV or IM once (oral dosing range; give parenterally for rapid reversal), which typically reverses the…
- Complications
Cervical spine degeneration: chronic cervical dystonia accelerates cervical spondylosis and can produce secondary radiculopathy or myelopathy.
- Prognosis
Focal adult-onset dystonia is typically chronic and slowly progressive, plateauing and rarely spreading beyond the initially affected and adjacent regions.
- Prevention
Avoid unnecessary dopamine-blocking antiemetics or antipsychotics in younger patients to reduce the risk of acute dystonic reactions and tardive dystonia; use the lowest effective dose for the…
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