Excerpt from Idiopathic Torsion Dystonia

Synonyms, Key Words, and Related Terms: DMD, dystonia musculorum deformans, movement disorder, Oppenheim disease, primary torsion dystonia

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Background: Dystonia is a syndrome of sustained muscle contractions, usually producing twisting and repetitive movements or abnormal postures (Fahn, 1987).

In 1908, Schwalbe first described primary/idiopathic torsion dystonia in a Jewish family, and in 1911, Oppenheim termed this dystonia musculorum deformans (DMD). Initially believed to be a manifestation of hysteria, idiopathic torsion dystonia gradually became established as a neurological entity with a genetic basis. DMD or Oppenheim disease are terms now used for childhood- and adolescent-onset dystonia due to the DYT1 gene.

With the recent mapping of genes for idiopathic torsion dystonia and identification of a gene for early onset dystonia, the description idiopathic/primary dystonia has become outdated; it now may be viewed as secondary to or symptomatic of an identified cause. However, continuing to use "primary" torsion dystonia to classify a group of dystonias as a clinically and genetically heterogenous group of movement disorders is justifiable on the basis that dystonia is the primary and sole abnormality attributable to the condition, and degeneration on pathologic examination is not known.

Primary torsion dystonia may be focal, segmental, multifocal, or generalized, depending on which anatomical sites are involved (see Table 1).

Table 1. Anatomic Distribution of Primary Torsion Dystonia

Focal Single Body Site
Segmental Contiguous body regions
Multifocal Multiple, noncontiguous body sites
Generalized Leg involvement with other body sites
Hemidystonia Unilateral

Pathophysiology: Although secondary forms of dystonia are associated frequently with structural lesions of the basal ganglia and thalamus, no consistent histologic or biochemical findings are noted in primary torsion dystonia.

No discernible abnormalities are seen on current neuroimaging studies.

Besides motor control difficulties, defective sensory processing is evident.

Current models of basal ganglia circuitry have been adapted, suggesting dysfunction at the basal ganglia level. These aberrations involve the direct and indirect pathways and result in impaired inhibition at the cortical level with consequent loss of normal inhibitory reflexes at the level of the brain stem and spinal levels.

See Image 1 for a diagram of the basal ganglia circuitry dysfunction in dystonia.

Frequency:

In the US: The relative frequencies of primary and secondary forms of dystonia are not known.
In the Movement Disorder Center at Columbia Presbyterian Medical Center, the vast majority (ie, 71%) of over 3000 patients with the disorder had primary torsion dystonia; the remaining 29% had secondary etiologies, with tardive dystonia being the leading acquired cause (unpublished data).
In a study from Rochester, Minnesota, the prevalence of generalized primary dystonia was reported to be 3.4 per 100,000 individuals and of focal primary dystonia, 29.5 per 100,000 individuals (Nutt, 1988).

Internationally: In a recent European collaborative study (Epidemiological Study of Dystonia in Europe [ESDE]), the investigators found a crude annual prevalence of 15.2 per 100,000 individuals, the majority having focal dystonia at a rate of 11.7 per 100,000 (ESDE Collaborative Group, 1999).

Race: Childhood- and adolescent-onset primary dystonia has been found to be more common in Jews of Eastern European or Ashkenazi ancestry.

Sex: In a large st .....