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Dystonia

Dystonia

Dystonia, a term first used by Oppenheim in 1911, is a motor syndrome of sustained involuntary muscle contractions causing twisting and repetitive movements, sometimes tremor, and/or abnormal postures. Dystonic movements may initially appear with voluntary movement of the affected part ("action dystonia") but may eventually occur with voluntary movement elsewhere in the body ("overflow"). The severity of dystonia may be reduced by sensory tricks (geste antagoniste), using tactile or proprioceptive stimuli to lessen or eliminate posturing; this feature is unique to dystonia. Dystonia may develop after muscle fatiguing activity, and patients with focal dystonias show more rapid fatigue than normals.

Dystonic disorders may be classified according to:

  • Age of onset: the most significant predictor of prognosis: worse with earlier onset;
  • Distribution: focal, segmental, multifocal, generalized, hemidystonia;
  • Etiology: primary/idiopathic vs. secondary/symptomatic.

Primary/idiopathic dystonias include:

  • Primary torsion dystonia (idiopathic torsion dystonia)
  • Severe generalized dystonia (dystonia musculorum deformans)
  • Segmental, multifocal and focal dystonias (e.g., torticollis, blepharospasm, writer’s cramp)
  • Dopa-responsive dystonia (DRD; Segawa’s syndrome)
  • Myoclonic dystonia

Secondary/symptomatic dystonia:

  • The differential diagnosis is broad (more than 40 known causes), including:
    • Heredodegenerative disorders: Wilson’s disease, Huntington’s disease, Hallervorden-Spatz disease, mitochondrial disorders, X- linked dystonia-parkinsonism (lubag)
    • Paroxysmal dystonias/dyskinesias: paroxysmal kinesigenic choreoathetosis/dystonia (PKC; usually responds to carbamazepine), and paroxysmal nonkinesigenic dystonia/choreoathetosis (PDC; does not respond to carbamazepine)
    • Metachromatic leukodystrophy
    • Gangliosidoses (GM1, GM2)
    • Perinatal cerebral injury
    • Encephalitis
    • Head trauma
    • Multiple sclerosis
    • Drugs/toxins, e.g., antipsychotic, antiemetic, and antidepressant drugs
    • Psychogenic

Appropriate investigations to exclude these symptomatic causes (especially Wilson’s disease) are appropriate.

The pathogenesis of dystonia is poorly understood. Different mechanism may apply in different conditions. Peripheral focal dystonias, such as torticollis and writer’s cramp, have been suggested to result from abnormal afferent information relayed from "stiff " muscle spindles. The genetic characterization of various dystonic syndromes may facilitate understanding of pathogenesis.

From a therapeutic point of view, one of the key questions relates to response to levodopa: dopa-responsive dystonia (DRD) responds very well to levodopa (and response fluctuations do not develop over time; cf. Parkinson’s disease). Other treatments which are sometimes helpful include anticholinergics, dopamine antagonists, dopamine agonists, and baclofen. Drug-induced dystonia following antipsychotic, antiemetic, or antidepressant drugs is often relieved within 20 minutes by intramuscular biperiden (5 mg) or procyclidine (5 mg). Botulinum toxin may be very helpful in some focal dystonias (e.g., blepharospasm). Surgery for dystonia using deep brain stimulation is still at the experimental stage.

 

References
Carvalho Aguiar PM de, Ozelius LJ. Classification and genetics of dystonia. Lancet Neurology 2002; 1: 316-325
Edwards M, Bhatia K. Dystonia. Advances in Clinical Neuroscience &Rehabilitation 2004; 4(2): 20,22,24
Fahn S, Marsden CD, Calne DB. Classification and investigation of dystonia. In: Marsden CD, Fahn S (eds.). Movement Disorders 2. London, Butterworth 1987: 332-358
Fahn S, Marsden CD. The treatment of dystonia. In: Marsden CD, Fahn S (eds.). Movement Disorders 2. London, Butterworth 1987: 359-382 Grunewald RA, Yoneda Y, Shipman JM, Sagar HJ. Idiopathic focal dystonia: a disorder of muscle spindle afferent processing? Brain 1997; 120: 2179-2185
Moore P, Naumann M (eds.). Handbook of botulinum toxin treatment
(2nd edition). Oxford: Blackwell Scientific, 2003
Németh AH. The genetics of primary dystonias and related disorders.
Brain 2002; 125: 695-721
Van Harten PN, Hoek HW, Kahn RS. Acute dystonia induced by drug treatment. BMJ 1999; 319: 623-626

 

Cross References

Anismus; Blepharospasm; Dysphonia; Eyelid apraxia; Fatigue; Gaping; Geste antagoniste; Hemidystonia; Torticollis; Writer’s cramp