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Boesch et al,1 reporting their experience with dystonia in multiple system atrophy (MSA), observed in 40% of untreated patients with anterocollis and unilateral limb dystonia representing the most frequent forms. All were MSA-P cases. Discussing the pathophysiology of dystonia, they quoted previous neuropathological studies attributing anterocollis to neuronal loss in the ventral putamen.2 In five of their 24 patients, four of whom were listed as levodopa responsive MSA-P, neuropathology confirmed the diagnosis of MSA, but the degree of degeneration varied considerably. As the neuropathology findings could not be included into this paper, these and other morphological data will be briefly discussed. In case 14 (woman aged 57 with four years duration) with unilateral end of dose focal dyskinesias, there were moderate fibrillary gliosis with minimal neuronal loss in the dorsolateal putamen and widespread glial cytoplasmic inclusions, considerable focal cell loss in the the caudal ventrolateral parts of the substantia nigra pars compacta (SNC) and locus coeruleus without Lewy bodies or pontine involvement, corresponding to MSA-P grade II.3,4 Case 18 with five years duration of illness and craniocervical peak dose dystonia, showed similar mild degeneration of the dorsolateral putmen and SNC (grade II), while cases 2 and 16 (disease duration four and five years, respectively) with generalised peak dose dystonia, histopathologically revealed subtotal neuronal loss and gliosis in the dorsolateral and, much less, in the anterior putamen and caudate nucleus associated with mild gliosis in the globus pallidus and degeneration of the SNC, more severe in the dorsolateral middle and caudal than in the medioventral and rostral parts, corresponding to MSA-P grade III.3,4 A review of necropsy cases of MSA with dystonia in the literature and eight personal cases gave the following results: among eight patients with anterocollis, five were MSA-P, and three MSA-C, all of the former with severe degeneration of the putamen, more severe in dorsolateral than ventral parts, and the SNC were all grade III. Among 28 cases with spastic and generalised dystonia, 21 were MSA-P and eight MSA-C. Twenty six brains revealed severe degeneration of the putamen, 12 of the caudate nucleus, seven of the globus pallidus, and all except for one had severe, rather diffuse involvement of the SNC. Only in single cases, the thalamus, corpus subthalamicum and other brain stem nuclei, for example, locus coeruleus, reticular SN, arcuate nucleus, etc, were involved. These data indicate that dystonia is more frequent in MSA-P than in MSA-C, in most but not all cases related to severe degeneration of the dorsolateral putamen and SNC with less involvement of the ventral putamen. While in MSA with spastic dystonia both the putamen and SNC appear equally involved, in MSA with dystonic contractures, the putamen appears more often affected than the SNC, whereas other subcortical and brain stem nuclei and the pontocerebellar system are only affected in single cases. This confirms previous studies on focal dystonia emphasising the role of the putamen as a major site of dysfunction5,6 with impairment of the basal ganglia circuitry.7 However, in view of the variability in the intensity and distribution of the neuropathological lesions in MSA with dystonia, further studies are needed for the elucidation of their pathophysiological basis.
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