Dystonia

01OverviewDefinition, clinical context and the essential points that orientate the chapter.

Dystonia reflects disordered motor-network control, sensory integration and inhibition rather than simple muscle spasm. The same patient may show sustained posture, mobile twisting movement and an irregular tremor. Pattern is the diagnostic anchor: a neck repeatedly rotates in one direction, fingers assume the same abnormal configuration during writing or eyelids contract involuntarily. A null point, mirror dystonia in the opposite hand and improvement from lightly touching the affected region can reveal the syndrome during examination.

Classification directs investigation. Adult-onset isolated focal cervical or cranial dystonia often needs no extensive test battery after expert assessment. Childhood or adolescent onset, generalisation, rapid progression, hemidystonia, seizures, cognitive change, parkinsonism, ataxia, neuropathy or systemic disease justifies MRI, metabolic, genetic or immune investigation. Medication chronology is mandatory: metoclopramide, prochlorperazine and antipsychotics are common causes of acute or tardive syndromes, and a long latency does not exclude exposure-related disease.

Treatment goals are specific: reduce pain, restore forward head position, keep eyes open, make speech understandable or recover a task. Botulinum toxin weakens selected overactive muscles temporarily, while physiotherapy and occupational strategies exploit motor learning, posture and task adaptation. Generalised or complex dystonia may need oral treatment and surgery. Functional dystonia is diagnosed from positive inconsistency or incongruence and treated respectfully through explanation and multidisciplinary rehabilitation, not dismissed as voluntary.

Key points

Dystonia consists of sustained or intermittent muscle contractions causing abnormal, often repetitive movements or postures that are patterned, twisting and sometimes tremulous.
It may be focal, segmental, multifocal, hemidystonic or generalised and is classified further by age at onset, temporal pattern and whether it is isolated, combined or secondary.
Movement is often action-induced and worsens with a specific task, fatigue or stress; overflow recruits nearby muscles and a geste antagoniste or sensory trick may transiently improve it.
Common focal syndromes include cervical dystonia, blepharospasm, laryngeal dystonia and task-specific hand dystonia such as writer's cramp.
Antipsychotics and dopamine-blocking antiemetics can cause an acute oculogyric, jaw, neck or truncal reaction within hours to days, or tardive dystonia after longer exposure.
Young-onset generalised dystonia requires assessment for genetic disease, Wilson disease and dopa-responsive dystonia; a specialist levodopa trial can be transformative in the last condition.
Sudden fixed painful posture is not automatically dystonia: stroke, seizure, tetany, tetanus, structural disease, orthopaedic deformity and functional dystonia need appropriate positive or exclusionary assessment.
Botulinum toxin is the main treatment for many functionally significant focal dystonias and must be delivered by an experienced injector with product-specific dosing and goals.
Oral trihexyphenidyl, baclofen, clonazepam or other medicines have selected roles, particularly in generalised disease, but anticholinergic, cognitive, sedation and dependence burdens often limit use.
Deep-brain stimulation, commonly targeting the globus pallidus internus, is considered for severe medication-refractory generalised or selected segmental disease through a specialist multidisciplinary service.

02AetiologyUnderlying causes, associations and risk factors, with why each one matters.

Isolated and inherited dystonia

Many focal adult syndromes are isolated, while younger-onset generalised disease may reflect inherited dopamine, basal-ganglia or synaptic disorders.

Structural and metabolic disease

Stroke, brain injury, tumour, cerebral palsy, Wilson disease and other metabolic disorders can produce secondary dystonia, often with additional neurological signs.

Medicine-induced syndromes

Dopamine-blocking antipsychotics and antiemetics cause acute or tardive dystonia; exposure chronology and concurrent akathisia or parkinsonism help identify iatrogenic disease.

Functional dystonia

A fixed painful posture, abrupt onset and internal inconsistency may support functional dystonia, diagnosed through positive features while recognising possible coexistence with organic disease.

03PathophysiologyThe causal sequence from the underlying abnormality to symptoms and harm.

1
Sensorimotor network dysfunction
Abnormal basal-ganglia, cerebellar and cortical integration impairs selection and scaling of intended movement and interpretation of sensory feedback.
2
Loss of reciprocal inhibition
Agonist and antagonist muscles activate together or in inappropriate sequence, creating sustained twisting, directional postures and overflow into nearby muscles.
3
Maladaptive plasticity
Repetition and abnormal sensory processing reinforce task-specific motor programmes, while a sensory trick can transiently reset network output.

04Clinical features and red flagsSymptoms, examination findings, patterns of presentation and time-critical warnings.

Cervical dystonia

The head repeatedly turns, tilts, flexes or extends in a patterned direction, often with shoulder elevation, neck pain, hypertrophied muscles, dystonic tremor and a hand-to-face sensory trick.

Task-specific hand dystonia

A reproducible abnormal finger, wrist or forearm posture appears during writing, instrument performance or another skilled task, with overflow and relative preservation of other actions early.

Cranial or laryngeal diseaseRed flag

Forceful blinking, jaw opening or closing, lower facial contraction or task-dependent strained or breathy voice reflects focal cranial network involvement; swallowing and airway impact determines urgency.

Acute drug reactionRed flag

Within hours or days of a dopamine blocker, painful torticollis, jaw spasm, tongue protrusion, opisthotonus or sustained upward eye deviation occurs, sometimes with frightening laryngeal involvement.

Young-onset progression

Foot inversion or task-related lower-limb posture begins in childhood and spreads, raising dopa-responsive and genetic dystonias, Wilson disease and other treatable metabolic causes.

Functional phenotype

A fixed posture has abrupt onset, marked inconsistency, unusual distribution or changes with distraction, alongside other positive functional neurological signs; pain and disability remain genuine.

05InvestigationsWhat to request, why it matters and how to interpret it.

Investigation order

Read from the initial assessment onwards. Tests may run in parallel in urgent care; first-line, preferred, confirmatory, definitive and gold-standard labels appear only when the chapter explicitly states them.

01
Phenomenology examination and videoFirst step
Why
Demonstrate pattern, task dependence, overflow, mirror movement, null point and sensory trick and define the muscles causing disability.
Interpretation and limitations
Examine at rest, during provoking tasks, walking and distraction. Video with consent aids multidisciplinary planning and injection comparison; do not infer cause from appearance alone.
02
Complete medication and toxin history
Why
Identify acute, tardive and secondary causes that need withdrawal or coordinated substitution.
Interpretation and limitations
Record antipsychotics, metoclopramide, prochlorperazine and previous exposure months or years earlier, plus illicit drugs and temporal relationships. Tardive symptoms may persist after the medicine stops.
03
MRI brain and relevant spine
Why
Investigate hemidystonia, rapid progression, young onset, focal neurological signs or an atypical painful fixed posture.
Interpretation and limitations
Basal-ganglia stroke, tumour, demyelination, structural cord disease and cerebral palsy sequelae may cause secondary dystonia. Normal imaging does not exclude genetic or functional disease.
04
Copper and metabolic assessment
Why
Find Wilson disease and other treatable metabolic causes in a young or systemically suggestive presentation.
Interpretation and limitations
Use liver profile, caeruloplasmin, copper studies, slit-lamp assessment and specialist interpretation rather than one screening result alone; select further metabolic tests from the phenotype.
05
Genetic and levodopa-responsive evaluation
Why
Identify inherited syndromes and a potentially dramatic response in childhood or young-onset generalised dystonia.
Interpretation and limitations
A movement-disorder or neurogenetics service chooses panels and counselling. A carefully monitored levodopa trial may be indicated even when family history is absent.
06
Functional, pain and allied-health assessment
Why
Set injection and rehabilitation targets and identify contracture, weakness or orthopaedic disease that limits reversibility.
Interpretation and limitations
Document range, pain, work, vision, voice, swallowing, writing and caregiving tasks. Electromyography or ultrasound can aid muscle targeting but does not by itself diagnose dystonia.

06Differential diagnosisRealistic alternatives and the features that help distinguish them.

Spasticity

Velocity-dependent resistance, brisk reflexes and a pyramidal distribution support upper motor-neurone spasticity rather than patterned twisting or task-specific posturing.

Rigidity

Uniform resistance through movement with bradykinesia and rest tremor favours parkinsonism; dystonia usually has a directional posture and muscle overactivity pattern.

Seizure, tetany or tetanus

Episodic altered awareness, carpopedal spasm with electrolyte disturbance or generalised painful spasm with infectious context requires urgent cause-specific assessment.

Orthopaedic or functional fixed posture

Fixed joint limitation persists during passive manipulation, while functional posture shows positive inconsistency; both can coexist with and obscure active dystonic contraction.

07ManagementImmediate care, first-line treatment, alternatives and escalation.

01Acute reactionProtect airway and reverse dopamine blockadeFirst stepPainful oculogyric, jaw, neck, tongue, truncal or laryngeal posturing follows a dopamine-blocking medicine.

1Use ABCDE, identify stridor, tongue or jaw obstruction and swallowing compromise, call anaesthetic support for airway involvement and stop the suspected culprit.
2Give parenteral procyclidine through the emergency protocol, commonly 5 to 10 mg intramuscularly or intravenously in an adult, and reassess promptly for response and recurrence.
3Observe according to severity and culprit half-life, document the adverse drug reaction accurately and communicate future antiemetic or antipsychotic avoidance and alternatives.
4If the posture does not respond as expected, revisit seizure, tetany, tetanus, structural neurological disease and functional presentations rather than repeatedly dosing blindly.

02Focal dystoniaInject for a defined taskCervical, cranial, laryngeal or limb dystonia causes pain, impaired function or social disability.

1Map the dystonic vector and provoking task, distinguish overactive from compensatory muscles and agree a goal such as forward gaze, reduced pain, writing or clearer speech.
2An expert injector chooses botulinum product, muscles, guidance method and dose, explaining delayed onset, temporary effect and local weakness, speech or swallowing risks.
3Review at peak and before wearing-off using the same goal measure, then adjust targeting or interval while adding phenotype-specific physiotherapy or occupational strategies.
4Investigate secondary causes when onset, distribution or associated signs are atypical rather than allowing repeated injections to replace diagnosis.

03Young or generalisedFind treatable biologyDystonia begins in childhood, spreads, generalises or accompanies parkinsonism, ataxia, seizures or systemic signs.

1Arrange movement-disorder review, MRI and phenotype-led Wilson, metabolic and genetic investigation with counselling for the patient and family.
2Undertake a supervised levodopa trial when dopa-responsive dystonia is plausible and measure gait, posture and daily function over an adequate period.
3Use oral anticholinergic, baclofen, clonazepam or focal injections cautiously around cognition, schooling, falls and respiratory or swallowing function.
4Refer severe medically refractory isolated or selected combined dystonia for multidisciplinary deep-brain-stimulation assessment before fixed deformity dominates.

04Functional dystoniaExplain positive signs and rehabilitateThe posture is diagnosed as functional using inconsistency or incongruence and an appropriate neurological assessment.

1Explain that positive examination signs show a problem with movement control rather than structural damage, validate symptoms and provide the diagnosis directly.
2Identify pain, fear, attention, sleep, mood and reinforcement factors without making psychological stress a required cause or implying deliberate production.
3EscalationUse functional-neurology-informed physiotherapy and occupational retraining, limit harmful immobilisation or escalating procedures and coordinate psychological treatment where useful.

Key medicines and prescribing safety6 treatments · regimens, roles and cautions

Rapid anticholinergic treatment usually reverses acute dopamine-blocker-induced oculogyric, cervical or generalised dystonia.

Procyclidine for acute dystonia

A common adult emergency dose is 5 to 10 mg intramuscularly or intravenously by protocol.

Airway care takes priority in laryngeal disease. Confusion, tachycardia, urinary retention and glaucoma risk matter, and persistent symptoms require diagnostic review or a protocol-led repeat dose.

First-choice symptomatic treatment for many focal dystonias, reducing pain and patterned overactivity for a limited period.

Botulinum toxin type A

Use product-specific units, muscle selection and intervals, commonly around twelve weeks, through an expert clinic.

Toxin products are not interchangeable. Local or remote weakness, dysphagia, dysphonia, dry eye and antibody-related loss of response require careful targeting and follow-up.

May improve generalised or segmental dystonia when injection treatment cannot cover the distribution.

Trihexyphenidyl

Begin at a low oral dose and titrate slowly under specialist supervision, particularly in younger patients.

Memory impairment, confusion, blurred vision, dry mouth, constipation, urinary retention and glaucoma often limit treatment, especially in older adults.

Can reduce painful generalised dystonia, spasms or combined spasticity and facilitate care.

Baclofen

Start low and increase gradually by response; specialist intrathecal therapy is reserved for selected severe disease.

Weakness, sedation and falls can worsen function; do not stop regular oral or intrathecal baclofen abruptly because severe withdrawal may occur.

Can produce dramatic, sustained improvement in dopa-responsive dystonia and is important in young-onset unexplained disease.

Levodopa trial

A movement-disorder specialist prescribes an age-appropriate low-dose trial and titrates to objective response.

Do not dismiss the diagnosis after inadequate dose or duration, and reassess atypical features, dyskinesia, nausea and postural symptoms during treatment.

Treats severe medication-refractory generalised or selected segmental dystonia before irreversible contracture when suitable.

Deep-brain stimulation

The functional-neurosurgery team implants and programs pallidal or other selected targets over serial visits.

Response varies by aetiology and may take months; infection, haemorrhage, hardware failure, stimulation effects, cognition and realistic functional goals require specialist consent.

08ComplicationsImportant consequences, why they occur and why they matter clinically.

Pain and contracture

Sustained muscle activation causes pain, tendon shortening and fixed joint deformity, making later movement and hygiene progressively harder.

Visual, speech or swallowing impairment

Blepharospasm, laryngeal and oromandibular dystonia can obstruct vision, communication, eating and occasionally airway safety in severe cases.

Functional and occupational disability

Task-specific hand, neck or generalised dystonia can prevent writing, driving, walking and employment despite preserved strength between affected tasks.

Treatment-related weakness

Botulinum toxin and systemic medicines may produce focal weakness, dysphagia, sedation or cognitive effects, requiring goal-based dosing and review.

09Monitoring and follow-upTreatment response, safety checks and longer-term review.

Measure the agreed functional goal, pain, posture and active range before injection, at expected peak response and as effect wears off so muscle selection evolves rationally.
Ask specifically about swallowing, voice, breathing, head drop, dry eye and generalised weakness after botulinum toxin, escalating possible toxin spread urgently.
Monitor cognition, vision, bowel and bladder function, sedation, falls and school or work performance during oral anticholinergic, baclofen or clonazepam treatment.
Revisit medication exposure, distribution and associated parkinsonism, ataxia, neuropathy, seizures, cognitive or systemic signs when dystonia progresses or generalises.
Track contracture, skin, seating, splints, pain, sleep, communication, mood and caregiver strain with physiotherapy, occupational and rehabilitation teams.
Provide emergency advice for new tongue or throat spasm, stridor, difficulty breathing or swallowing, particularly after antipsychotic or antiemetic exposure.

10Special situationsVariants, exceptions and circumstances that change the usual approach.

Pattern beats force

Dystonia is recognised by repeated directional organisation and task dependence rather than how strong, painful or dramatic the contraction appears.

Sensory tricks are real

A light touch can transiently normalise abnormal network output without mechanically moving the body part and strongly supports dystonic phenomenology.

The normal muscle compensates

An apparently overactive muscle may be trying to restore posture; indiscriminate injection can remove compensation and worsen the functional vector.

Tardive onset can lag

A dopamine-blocker exposure months or years earlier remains relevant because tardive dystonia may persist or emerge after dose reduction.

Dopa response is high value

In a child or young adult with limb-onset dystonia and diurnal fluctuation, a supervised levodopa trial can uncover a highly treatable disorder.

Fixed does not mean structural

Functional dystonia may be continuously fixed and painful; positive inconsistency plus an appropriate examination supports a treatable control disorder.

11Common pitfallsFrequent interpretation and management errors.

01
Calling painful neck spasm musculoskeletal without observing patterned posture, tremor, null point or a sensory trick.
02
Missing metoclopramide, prochlorperazine or antipsychotic exposure in acute torticollis or oculogyric crisis.
03
Treating laryngeal dystonia as anxiety while stridor and respiratory compromise evolve.
04
Repeating botulinum toxin into visibly active compensatory muscles without a directional analysis or functional goal.
05
Failing to investigate Wilson disease or offer a specialist levodopa trial in young progressive generalised dystonia.
06
Labelling functional dystonia as fabricated rather than demonstrating positive signs and offering rehabilitation.