Dystonia, Idiopathic Torsion

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 disorder

  • The gene responsible for 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 ...