DYSTONIC DISORDERS
DEFINITION:
A group of disorders characterized by slow, involuntary,
repetitive movements causing exaggerated twisting and posturing of
the extremities and/or trunk.
EPIDEMIOLOGY:
- prevalence: 4/10,000
- age of onset:
- risk factors:
- see differential diagnosis
DIFFERENTIAL DIAGNOSIS:
CLINICAL FEATURES:
1. Dystonic Characteristics
- slow, involuntary, repetitive movements causing exaggerated
twisting and posturing of various muscle groups
- extremities
- axial musculature
- cranial and cervical muscles
- may also involve segmental dystonia
- writer's cramp
- blepharospasm
- buccomandibular dystonia
- focal, hemidystonic, or generalized
2. Features Suggestive of Secondary Etiology
- onset in infancy
- acute or sudden onset
- presence of dystonia at rest from onset
- unilateral involvement or hemidystonia
- absence of family history of dystonia, tremor, or other
movement disorders
- exposure to risk factors: drugs, trauma, infection
3. Tics Caused by Birth Asphyxia
- delayed onset of dystonia - mean age of onset is 12.9 yrs
- types of dystonia observed:
- generalized, hemidystonic, segmental brachial
- tend to evolve into generalized dystonia
- other associated neurologic manifestations:
- developmental delay, hyperreflexia, dysmetria, focal
weakness
- respond well to high-dose artane (anti-cholinergic)
4. Tics Caused by Trauma
- head, neck, peripheral nerve trauma
- types of dystonia observed:
- generalized, hemidystonic, cervical
- other associated neurologic manifestations:
- hemiparesis, aphasia, seizures
- usually respond poorly to medical and surgical therapy
INVESTIGATIONS:
1. Serum
- CBC, ESR, electrolytes, gas, copper, ceruloplasmin
- ANA, protein electrophoresis
- serum lactate, pyruvate, amino acids
- biopterin, homovanillic acid
2. Urine
- screen for amino acids, organic acids, and oligosaccharides
3. Imaging Studies
4. Others
- EEG
- muscle biopsy
- psychometric testing
MANAGEMENT:
1. Primary Dystonias
1. Generalized
1. Carbodopa-Levodopa (Sinemet)
- initial trial to rule out Dopa-Responsive Dystonia
2. Trihexphenidyl (Artane)
- for Idiopathic Torsion Dystonia
3. Surgical
- for patients who failed medical therapy with severe
dystonia
- cryothalamectomy -> lesion in ventrolateral thalamus
2. Localized
1. Medical
- clonazepam or lorazepam - for cranial & cervical
dystonias
- baclofen - for oromandibular dystonia
- others - pimozide, tetrabenazine
2. Clostridium botulinum toxin A
- local injections for cranial, cervical, and other focal
dystonias
- chemodenervation - prevents release of acetylcholine
- symptomatic benefit for 3-5 months
- side effects: weakness at site of injection
2. Secondary Dystonias
- correct underlying disorder
- remove offending drug - i.e., benadryl 1-2 mg/kg/dose IV
- treat dystonias
|