Dystonia and Tardive Dyskinesia
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Direct answer
Dystonia is sustained involuntary muscle contraction that produces twisting postures, while tardive dyskinesia is a delayed, stereotyped movement disorder caused by long-term dopamine receptor blockade. Acute dystonic reactions follow an antipsychotic or metoclopramide within hours to days and respond to an anticholinergic or antihistamine. Tardive dyskinesia is managed by reducing the offending drug, and VMAT2 inhibitors such as valbenazine are used when symptoms persist.
What you must remember
- Acute dystonic reaction: sudden onset within hours to days of a dopamine blocker, often in young men, with torticollis, trismus or an oculogyric crisis.
- Acute dystonia treatment: an anticholinergic such as benztropine or an antihistamine such as diphenhydramine gives rapid relief, and the offending drug is stopped.
- Tardive syndromes: usually develop after three months or more of dopamine antagonist exposure (sooner in older adults), most often as orofacial dyskinesia with lip smacking, chewing and tongue movements.
- Tardive dyskinesia management: stop or reduce the offending drug where possible, and use valbenazine or deutetrabenazine, both VMAT2 inhibitors, for persistent symptoms.
- Cervical dystonia: focal dystonia of the neck causing torticollis, laterocollis or retrocollis, with a sensory trick that temporarily relieves the posture.
- Botulinum toxin: the first-line treatment for cervical dystonia and blepharospasm, with repeat injections needed as the effect wears off over months.
- Dopa-responsive dystonia: childhood onset, diurnal variation worst in the evening, and a dramatic response to low-dose levodopa, linked with GCH1 mutations.
Comparing three dystonic presentations
A 24-year-old man started on haloperidol for psychosis develops his neck twisted to one side within a day, while a 58-year-old woman on long-term metoclopramide has rhythmic lip smacking after a year. The table separates the two drug-related pictures from idiopathic cervical dystonia.
| Feature | Acute dystonia | Tardive dyskinesia | Cervical dystonia |
|---|---|---|---|
| Onset | Hours to days after a dopamine blocker | Months to years of exposure | Gradual, often in middle age |
| Typical movement | Torticollis, trismus, oculogyric crisis | Orofacial chewing and tongue movements | Head turning or tilting, sometimes tremor |
| Drug link | Dopamine antagonists | Long-term dopamine antagonists | Usually none |
| Usual treatment | Anticholinergic or antihistamine | Stop drug, VMAT2 inhibitor | Botulinum toxin |
Timing separates the two drug-related disorders, since acute dystonia appears early and tardive dyskinesia appears late. Cervical dystonia is usually idiopathic, so a careful drug history is still needed before the diagnosis is made. Dopamine blockade explains the first two columns, which is why the drug history is the first question in any movement disorder.
Where the stem misleads on movement disorders
Most errors come from ignoring the timing of symptoms relative to drug exposure.
- Trap: labelling an acute dystonic reaction as a psychiatric symptom Correct: it is an extrapyramidal adverse effect that responds promptly to benztropine or diphenhydramine.
- Trap: adding an anticholinergic for tardive dyskinesia Correct: anticholinergics are not the treatment for tardive dyskinesia and may worsen it, so a VMAT2 inhibitor is the targeted option.
- Trap: assuming tardive dyskinesia reverses once the antipsychotic is switched Correct: many cases persist, so the drug load is reduced where possible and a VMAT2 inhibitor is considered.
- Trap: overlooking Wilson disease in a young patient with dystonia Correct: Wilson disease causes dystonia with hepatic or psychiatric features and needs caeruloplasmin and urinary copper testing.
Frequently asked questions
What distinguishes acute dystonic reaction from tardive dyskinesia?
Acute dystonic reaction appears within hours to days of starting a dopamine antagonist and causes sustained postures such as torticollis. Tardive dyskinesia develops after months to years of exposure and causes stereotyped orofacial movements, which may persist after the drug is stopped.
Which drugs treat an acute dystonic reaction quickly?
Anticholinergics such as benztropine or antihistamines such as diphenhydramine relieve an acute dystonic reaction quickly. The offending dopamine antagonist is also stopped, and symptoms usually settle within hours of treatment.
Why is botulinum toxin used in cervical dystonia?
Botulinum toxin is injected into the affected neck muscles to weaken the overactive contraction that causes torticollis. It is the first-line treatment for cervical dystonia, and repeat injections are needed because the effect wears off over months.
Which drugs treat persistent tardive dyskinesia?
VMAT2 inhibitors such as valbenazine and deutetrabenazine are the recognised targeted treatments for persistent tardive dyskinesia. They deplete presynaptic dopamine, so depression and parkinsonism need monitoring during treatment.
Why must Wilson disease be excluded in young patients with dystonia?
Wilson disease causes dystonia in young patients alongside hepatic and psychiatric features, and it is treatable when detected early. Serum caeruloplasmin, urinary copper and slit-lamp examination for Kayser-Fleischer rings are the standard screening tests.