Dystonia
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Direct answer
Dystonia is a hyperkinetic movement disorder of sustained or intermittent muscle contractions producing twisting, repetitive movements and abnormal postures, often task-specific and frequently relieved by a sensory trick (geste antagoniste). It is classified along two axes: clinical characteristics (age at onset, body distribution, temporal pattern) and aetiology (isolated, combined, acquired or functional). Focal dystonia in adults — cervical, blepharospasm, task-specific hand — responds best to botulinum toxin; every child or young adult with dystonia deserves a levodopa trial and Wilson disease screening first.
What you must remember
- Phenomenology: patterned twisting movements with overflow, task specificity such as writer's cramp, a geste antagoniste such as touching the cheek in cervical dystonia, and irregular position-dependent dystonic tremor.
- Distribution terms: focal (cervical commonest in adults, then blepharospasm and oromandibular), segmental, multifocal, generalised and hemidystonia, the last often signalling a contralateral structural lesion.
- Hereditary isolated syndromes: DYT1 (TOR1A) generalised dystonia beginning in a leg in childhood or adolescence; dopa-responsive dystonia (GCH1) with diurnal worsening, gait onset in girls and dramatic response to small levodopa doses.
- Combined and acquired causes: Wilson disease, neurodegeneration with brain iron accumulation, kernicterus, post-stroke dystonia and dopamine-antagonist exposure.
- Mandatory workup in young-onset dystonia: slit-lamp examination for Kayser-Fleischer rings, ceruloplasmin and 24-hour urinary copper, brain iron imaging when suggested, and a therapeutic levodopa trial — dopa-responsive dystonia is cheap to diagnose and lifelong to treat.
- Treatment ladder: botulinum toxin is first-line and most effective for cervical dystonia and blepharospasm; oral agents (trihexyphenidyl in younger patients, tetrabenazine, baclofen) add modest benefit; pallidal deep brain stimulation transforms selected refractory cases.
- Drug-related dystonia in two forms: acute dystonic reactions within hours of a dopamine antagonist, and tardive dystonia after chronic exposure, typically oromandibular, treated by withdrawal plus valbenazine or deutetrabenazine where available. Status dystonicus — sustained severe attacks with hyperthermia and rhabdomyolysis — is a movement disorder emergency requiring intensive care.
Common confusion
Cervical dystonia is labelled orthopaedic or psychiatric because pain and posturing mimic musculoskeletal disease; the geste antagoniste betrays the basal ganglion origin. Tardive dystonia is mistaken for worsening primary disease when the antipsychotic history has not been extracted. In children, dopa-responsive dystonia masquerades as cerebral palsy until a levodopa trial unlocks the gait — which is why "trial levodopa" is a safe answer in young-onset dystonia. Finally, dystonic tremor is irregular and position-dependent, unlike the bilateral rhythmic postural tremor of essential tremor.
Exam-focused takeaway
Three answers dominate: sensory trick for the definition, botulinum toxin for focal treatment, and Wilson screening plus levodopa trial for young-onset disease. Remember TOR1A for generalised adolescent-onset dystonia and GCH1 for the girl who walks normally in the morning and deteriorates by evening. Status dystonicus and acute dystonic reactions link this page to movement disorder emergencies.
Frequently asked questions
What is a geste antagoniste?
A sensory trick — lightly touching the cheek or chin — that transiently improves dystonic posturing, classically in cervical dystonia.
Which investigations are needed in young-onset dystonia?
Slit-lamp examination for Kayser-Fleischer rings, ceruloplasmin and 24-hour urinary copper for Wilson disease, brain iron imaging when suggested, and a levodopa trial.
What is the first-line treatment of cervical dystonia?
Botulinum toxin injections into overactive muscles, which outperform oral drugs for both posturing and pain.
What is dopa-responsive dystonia?
A GCH1-related dystonia with childhood gait onset and diurnal fluctuation responding dramatically to low-dose levodopa.
Why is Wilson disease screening important?
It is a treatable combined dystonia whose missed diagnosis costs both liver and brain; ocular and copper studies are cheap and definitive when positive.