The anatomical basis of symptomatic hemidystonia.

Twenty-eight patients with focal (arm or leg) or hemidystonia due to tumour, arteriovenous malformation, infarction, haemorrhage or hemiatrophy are described. All had typical dystonic movements and/or postures, identical to those seen in idiopathic (primary) torsion dystonia. The site(s) of the lesion responsible, as defined by CT (computerized tomography) scan or pathological examination, was in the contralateral caudate nucleus, lentiform nucleus (particularly the putamen) or thalamus, or in a combination of these structures. Review of 13 other patients in the literature with hemidystonia and lesions defined by CT scan, and of 7 other patients with pathologically discrete lesions associated with hemidystonia, also indicated involvement of these structures. Dystonia may be due to abnormal input from thalamus to premotor cortex, due to lesions either of the thalamus itself, or of the striatum projecting by way of the globus pallidus to the thalamus.