Dystonia
Dystonia
What You'll Learn
- Definition: sustained or intermittent muscle contractions causing abnormal, often repetitive movements and/or postures; may be patterned or twisting
- Sensory trick (geste antagoniste): light touch to affected area reduces dystonic posture — highly specific for dystonia
- DYT-TOR1A (DYT1): most common inherited childhood-onset generalized dystonia; Ashkenazi Jewish; GAG deletion in TOR1A gene
- Cervical dystonia: most common focal dystonia in adults; botulinum toxin is first-line treatment
- Dopa-responsive dystonia (DYT-GCH1/Segawa disease): diurnal fluctuation, dramatic sustained levodopa response — trial levodopa in ALL young-onset dystonia
- Treatment: botulinum toxin (focal), trihexyphenidyl (generalized, especially children), GPi DBS (refractory generalized/DYT-TOR1A)
HighYield Pearls
- Levodopa trial in ALL young/adult dystonia: exclude dopa-responsive dystonia (DYT5/GCH1, female predominant, childhood-onset with diurnal fluctuation, exquisite sustained low-dose levodopa response)
- DYT1 (TOR1A, AD ~30% penetrance): childhood-onset generalized dystonia, Ashkenazi Jewish, starts in leg/arm → generalizes; best DBS (GPi) responder
- Cervical dystonia = most common focal dystonia: geste antagoniste (sensory trick) classic; botulinum toxin 1st-line
- Meige syndrome: blepharospasm + oromandibular dystonia → botulinum toxin
- Focal task-specific dystonia (writer’s cramp, musician’s cramp): only during specific task; young/middle-age
- Dystonic storm / status dystonicus: generalized severe dystonia + fever + rhabdomyolysis + renal failure → ICU, sedation, intubation; consider urgent GPi DBS
- Acute dystonic reaction: drug-induced (metoclopramide, antipsychotics) → IV anticholinergic (diphenhydramine, benztropine)
- Tardive dystonia (chronic neuroleptic exposure) ≠ acute dystonic reaction; treat with focal botulinum toxin, trihexyphenidyl or clonazepam, and GPi DBS for refractory cases. VMAT2 inhibitors may help, but evidence is stronger for tardive dyskinesia than tardive dystonia.
- DBS GPi for medication-refractory dystonia: best response in DYT1 generalized; benefit emerges over weeks/months (vs minutes in PD)
- Wilson disease in young dystonia: check serum ceruloplasmin + 24h urine copper + slit lamp for KF rings + LFTs
- Adult-onset secondary causes: stroke (hemidystonia), Wilson, manganese, MS, vasculitis, PKAN/NBIA, Huntington (juvenile dystonic-rigid), tumor, encephalitis (anti-NMDAR orofacial dyskinesias, anti-DPPX)
🔍 Quick ReferenceClinical · Imaging · Genetics / pathology
Clinical phenotype
- Geste antagoniste (sensory trick relieves posture) → cervical dystonia (and other focal dystonias)
- Diurnal fluctuation, worsens through the day → DYT5 dopa-responsive dystonia (GCH1)
- Exquisite sustained response to low-dose levodopa → dopa-responsive dystonia (Segawa)
- Action-induced / task-specific dystonia → writer’s cramp, musician’s cramp
- Retrocollis → drug-induced (tardive / acute dystonic reaction)
- Torticollis + laterocollis + shoulder elevation → cervical dystonia
- Blepharospasm + oromandibular dystonia → Meige syndrome
- Camptocormia (anterior trunk flexion) → axial dystonia (PD, MSA, isolated)
- Pisa syndrome (lateral truncal lean) → axial dystonia (MSA, PD, drug-induced)
- Foot inversion + plantarflexion at onset (leg start) → DYT1 generalized dystonia
- Wing-beating tremor + dysarthria + KF rings → Wilson disease
- Heredodegenerative dystonia + cognitive decline → juvenile Huntington (Westphal variant)
- Generalized dystonia + fever + rhabdomyolysis + renal failure → dystonic storm / status dystonicus
Imaging signs
- Normal MRI → primary (isolated) dystonia
- Basal ganglia T2 hyperintensity → secondary dystonia (Wilson, manganese, Leigh, PKAN, hypoxia)
- “Eye of the tiger” sign (T2 hypointense GP with central hyperintensity) → PKAN (NBIA)
- Bright T1 globus pallidus (manganese deposition) → chronic liver disease / manganese toxicity
- “Face of the giant panda” midbrain sign → Wilson disease
- Contralateral basal ganglia lesion on MRI → hemidystonia (stroke, tumor, AVM)
Genetics / pathology / treatment pearls
- TOR1A / DYT1, AD reduced penetrance, Ashkenazi → childhood generalized dystonia (best DBS responder)
- GCH1 / DYT5, AD, female predominant → dopa-responsive dystonia (Segawa)
- TH / AR (autosomal recessive) → infantile dystonia-parkinsonism
- ATP1A3 → alternating hemiplegia of childhood OR rapid-onset dystonia-parkinsonism (RDP)
- PANK2 / PKAN → NBIA with eye-of-the-tiger sign
- ATP7B → Wilson disease (KF rings, low ceruloplasmin)
- HTT (CAG expansion) → juvenile Huntington (dystonic-rigid Westphal variant)
- Botulinum toxin (BoNT-A: onabotulinum/abobotulinum/incobotulinum; BoNT-B: rimabotulinum) → 1st-line focal dystonia
- DBS GPi → refractory generalized dystonia (DYT1 best response)
- Focal botulinum toxin, trihexyphenidyl/clonazepam, GPi DBS for refractory cases → tardive dystonia (VMAT2 inhibitors may help, but evidence is stronger for tardive dyskinesia than tardive dystonia)
- Levodopa trial → mandatory in ALL adult/young dystonia (exclude DYT5)
Classification
Dystonia is classified along two axes per the 2013 international consensus update:
Axis 1: Clinical Characteristics
Age at Onset
- Infancy: birth–2 years
- Childhood: 3–12 years
- Adolescence: 13–20 years
- Early adulthood: 21–40 years
- Late adulthood: >40 years
- Earlier onset → greater tendency to generalize; later onset → more likely to remain focal
Body Distribution
| Distribution | Definition | Examples |
|---|---|---|
| Focal | Single body region | Cervical dystonia, blepharospasm, writer’s cramp, spasmodic dysphonia |
| Segmental | ≥2 contiguous body regions | Cranial + cervical (Meige syndrome + torticollis) |
| Multifocal | ≥2 non-contiguous body regions | Arm + leg on opposite sides |
| Generalized | Trunk + ≥2 other regions | DYT-TOR1A with limb + trunk involvement |
| Hemidystonia | Ipsilateral arm + leg | Contralateral basal ganglia lesion (stroke, tumor) |
Temporal Pattern
- Persistent: present throughout the day
- Action-specific: only during specific tasks (e.g., writer’s cramp)
- Diurnal fluctuation: worsens as day progresses (classic for dopa-responsive dystonia)
- Paroxysmal: sudden episodes of dystonia (paroxysmal kinesigenic and non-kinesigenic dystonias)
Associated Features
- Isolated dystonia: dystonia is the only motor feature (with or without tremor)
- Combined dystonia: dystonia + another movement disorder (myoclonus, parkinsonism)
Axis 2: Etiology
- Inherited: autosomal dominant (DYT-TOR1A, DYT-THAP1, DYT-GCH1), autosomal recessive, X-linked, mitochondrial
- Acquired: perinatal brain injury/CP, infection, drugs (tardive), toxins, vascular, neoplastic, brain injury
- Idiopathic: sporadic or familial, no identified cause
💎 Board Pearl
- Hemidystonia in an adult = structural contralateral basal ganglia lesion until proven otherwise — always image (stroke, tumor, AVM). In a child, consider delayed-onset dystonia after perinatal basal ganglia injury.
- Earlier onset predicts more severe, widespread disease; focal adult-onset dystonia rarely generalizes.
Genetic Dystonias
| Gene/Locus | Inheritance | Onset | Distribution | Key Features |
|---|---|---|---|---|
| DYT-TOR1A (DYT1) | AD (30% penetrance) | Childhood (mean ~12 yr) | Generalized (starts in limb) | GAG deletion in TOR1A; Ashkenazi Jewish carrier frequency ~1:2,000–6,000 (5–10× higher than non-Jewish); ~30% penetrance; begins in leg/arm → generalizes; spares cranial muscles; best DBS responder |
| DYT-THAP1 (DYT6) | AD | Adolescence/young adult | Cranio-cervical, segmental | Prominent cranial and cervical involvement; laryngeal dystonia common; less likely to generalize than DYT1 |
| DYT-KMT2B | AD (often de novo) | Childhood | Generalized | Childhood-onset generalized dystonia; frequently associated with intellectual disability, short stature, microcephaly; good DBS response |
| DYT-SGCE (DYT11) | AD (maternal imprinting) | Childhood/adolescence | Myoclonus-dystonia | Myoclonus (lightning jerks) + dystonia; alcohol-responsive; psychiatric comorbidities (OCD, anxiety); epsilon-sarcoglycan gene; maternal imprinting → disease only when inherited from father |
| DYT-GCH1 (DYT5a) | AD | Childhood (mean ~6 yr) | Starts in leg → generalized | Dopa-responsive dystonia (Segawa disease); diurnal fluctuation; dramatic sustained response to low-dose levodopa; GTP cyclohydrolase 1 deficiency; normal DaTSCAN |
| DYT/PARK-TH (DYT5b) | AR | Infancy/childhood | Generalized | Tyrosine hydroxylase deficiency; more severe than DYT-GCH1; encephalopathy, parkinsonism; partial levodopa response |
| DYT-ANO3 (DYT24) | AD | Adult | Cranio-cervical | AD craniocervical dystonia + tremor; may mimic essential tremor; ANO3 (anoctamin-3) gene |
| DYT-TAF1 (DYT3, Lubag) | X-linked recessive | Adult | Generalized dystonia-parkinsonism | Filipino ancestry, Panay island; adult-onset dystonia evolving into parkinsonism; TAF1 gene |
| DYT-ATP1A3 (DYT12, RDP) | AD | Adolescence/young adult | Generalized dystonia-parkinsonism | Rapid-onset dystonia-parkinsonism — sudden onset over hours–days; rostrocaudal gradient (face > arm > leg); often triggered by fever, stress, or exercise; ATP1A3 also causes alternating hemiplegia of childhood |
| DYT-PRKRA (DYT16) | AR | Young-onset | Generalized dystonia-parkinsonism | Young-onset generalized dystonia-parkinsonism; described in Brazilian families; PRKRA gene |
| DYT-GNAL (DYT25) | AD | Adult | Cervical (cranio-cervical) | Adult-onset cervical dystonia; GNAL gene (G-protein alpha subunit) |
💎 Board Pearl
- DYT-TOR1A: test any Ashkenazi Jewish child with limb-onset dystonia; GAG deletion is a 3-bp in-frame deletion; 30% penetrance means many carriers are unaffected.
- DYT-SGCE (myoclonus-dystonia): maternal imprinting = only symptomatic when inherited from father. Alcohol responsiveness is characteristic but not an indication for alcohol use.
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