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Key Features

Essentials of Diagnosis

  • Dystonic movements and postures

  • No other neurologic signs

  • Normal birth and developmental history

  • Investigations (including CT scan or MRI) reveal no cause of dystonia

General Considerations

  • May occur sporadically or on a hereditary basis, with autosomal dominant, autosomal recessive, and X-linked recessive modes of transmission

  • One responsible gene is located at 9q34 (and has been named DYT1)

    • Involves a unique mutation consisting of a GAG deletion in the major dominantly inherited disorder and maps to the long arm of the X chromosome in the X-linked recessive form

    • The responsible gene in the autosomal recessive disorder is unknown

  • Symptoms may begin in childhood or later and persist throughout life

Clinical Findings

Symptoms and Signs

  • Onset of abnormal movements and postures in a patient with

    • A normal birth and developmental history

    • No relevant past medical illness

    • No other neurologic signs

  • Dystonic movements of the head and neck

    • Torticollis

    • Blepharospasm

    • Facial grimacing

    • Forced opening or closing of the mouth

  • The limbs may also adopt abnormal but characteristic postures

  • The age at onset influences both the clinical findings and the prognosis

  • Childhood onset

    • A family history of the disorder is usual

    • Initial symptoms commonly in the legs

    • Progression is likely until there is severe disability from generalized dystonia

  • Adult onset

    • A positive family history is unlikely

    • Initial symptoms are often in the arms or axial structures

    • Severe disability does not usually occur, although generalized dystonia may ultimately develop in some patients

Differential Diagnosis

  • Perinatal anoxia

  • Birth trauma

  • Neonatal kernicterus

  • Wilson disease

  • Huntington disease

  • Parkinsonism

  • Sequela of encephalitis lethargica

  • Neuroleptic drug therapy

  • Dopa-responsive dystonia

Diagnosis

Imaging Studies

  • Investigations (including MRI or CT imaging) reveal no cause for the abnormal movements

Treatment

Medications

  • Idiopathic torsion dystonia usually responds poorly to drugs

  • Levodopa, diazepam, baclofen, carbamazepine, amantadine, or anticholinergic medication such as trihexyphenidyl or benztropine (in high dosage) occasionally helpful

  • If not, a trial of treatment with tetrabenazine, phenothiazines, or haloperidol may be worthwhile

  • In each case, the dose has to be individualized, depending on response and tolerance

  • However, the doses of tetrabenazine, phenothiazines, or haloperidol required for benefit usually lead to mild parkinsonism

Therapeutic Procedures

  • Pallidal deep brain stimulation

    • Helpful for medically refractory dystonia

    • Has a lower morbidity than stereotactic thalamotomy, which is sometimes helpful in patients with predominantly unilateral limb dystonia

    • Potential adverse events include cerebral infection or hemorrhage, broken leads, affective changes, and dysarthria

Outcome

Prognosis

  • A distinct variety of dominantly inherited dystonia, caused by a mutation in gene for GTP cyclohydrolase I on chromosome 14q, is remarkably responsive to levodopa; therefore ...

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