Dystonia is a movement disorder characterized by sustained or intermittent muscle contractions producing abnormal, often repetitive movements or postures. The contractions are often action-induced or task-specific, can be tremulous, and frequently involve overflow to nearby muscle groups. Distinguished from other movement disorders by the sustained quality and characteristic postures.
Classification by anatomy:
Focal dystonia — single body part. Common types: cervical dystonia (torticollis — head turning, tilting, pulling), blepharospasm (forced eye closure), oromandibular dystonia (jaw/tongue), writer's cramp and other task-specific occupational dystonias (musicians, typists), spasmodic dysphonia (voice).
Segmental dystonia — adjacent body parts.
Multifocal dystonia — non-adjacent body parts.
Generalized dystonia — trunk plus two other regions. Typically young-onset, often genetic.
Hemidystonia — one side of body, suggesting acquired cause (stroke, trauma, demyelination).
Classification by etiology:
Primary (isolated) dystonia — genetic causes: DYT1 (early-onset generalized dystonia from TOR1A mutation), DYT5/dopa-responsive dystonia (GCH1 mutation — dramatic response to low-dose levodopa), DYT11 myoclonus-dystonia, others.
Secondary dystonia — stroke, perinatal injury, head trauma, demyelination, medications (tardive dystonia from antipsychotic D2 blockade, acute dystonic reactions from antipsychotics), Wilson's disease (always rule out in young-onset dystonia), neurodegenerative disorders.
Psychogenic/functional dystonia — features incompatible with classical patterns, often abrupt onset, distractibility, variability.
Always trial low-dose levodopa in young-onset dystonia. Dopa-responsive dystonia (Segawa syndrome) is caused by GCH1 mutations producing impaired BH4 synthesis and dopamine deficiency in basal ganglia. Symptoms can dramatically resolve with very low-dose levodopa (50-200 mg/day). Untreated, progresses to disabling generalized dystonia. The therapeutic trial is appropriate in any young-onset dystonia — if dopa-responsive, transformation is dramatic.
Treatment by type:
Focal dystonias: botulinum toxin injections are first-line. Highly effective for cervical dystonia, blepharospasm, oromandibular, writer's cramp, spasmodic dysphonia. Repeated every 3-4 months. Trained injectors essential.
Oral medications: anticholinergics (trihexyphenidyl), baclofen, benzodiazepines, tetrabenazine. Variable effectiveness, side effect-limited. Trial-and-error often required.
Generalized dystonia: oral medications combined. Deep brain stimulation of globus pallidus internus increasingly used — substantial improvement in many genetic generalized dystonias.
Tardive dystonia: consider switching antipsychotic; VMAT2 inhibitors; botulinum toxin for focal manifestations.
When you encounter a patient with dystonia, identify subtype (focal vs generalized), age of onset, family history, medication exposure, and trial low-dose levodopa in young patients. Botulinum toxin for focal forms; oral medications and DBS for generalized. The disorders are treatable; many patients have struggled without diagnosis for years.