gms | German Medical Science

Objective: The underlying neuroanatomical substrate for primary dystonia is poorly understood and so are its neuropathological causes on a molecular basis. Primary dystonia is assumed to lack any morphological substrate. In dystonia patients receiving DBS, a strikingly high number of T2- hyperintensities were seen within the globus pallidus (GP) target region even in very young patients, where ischemia or microvascular lesions appear highly unlikely. This observation prompted us to quantify the T2-hyperintensive lesions found. We considered the hypothesis there might in fact be anatomical substrate for dystonia within the GP.

Method: 50 patients with a diagnosis of primary dystonia treated with DBS were age-matched to 50 healthy controls. Both groups had thin-sliced T2-weight MRI sequences. Using Brain Lab’s iPlan 4.0 navigation software, volumes of the hyperintensities and total GP volumes (as well as volumes of all other basal ganglia, BG) were calculated. Total BG volumes and volume: lesion ratios were compared between the groups. Volumetry results were then correlated to clinical features of the patients.

Results: The percentaged fraction of T2 hyperintensities within the GPi was ten-fold higher in dystonia patients, 4% (± 7,2 SD) as compared to 0.05% (± 0.1 SD) in the control population, p<0.0001. The difference in lesion volumes was greatest in younger patients <25y. No clear correlation of lesion site to clinical dominance was retraced. Total GP volumes were considerably larger in the dystonia group (1545mm³ (± 377) vs 1170mm³ (± 205), p< 0.005), while the volumes of putamen and caudate were significantly smaller (3969mm³ (± 524) vs 3297mm³ (± 801), p<0.005; and 3192mm³ (± 469) vs 2421mm³ (± 576), p<0.005, respectively).

Conclusions: Basal ganglia volumes in dystonia patients differ from those in a the healthy population. Our data suggests a degeneration of putamen and caudate nucleus and an enlarement of the GPi, possibly due to overexcitation. T2-hyperintensive lesions in the GP are more common in dystonia patients,-even in primary dystonia, than in the normal population and are found even in children and adolescents. Their nature remains unclear.