Increased insula-putamen connectivity in X-linked dystonia-parkinsonism.

Preliminary evidence from postmortem studies of X-linked dystonia-parkinsonism (XDP) suggests tissue loss may occur first and/or most severely in the striatal striosome compartment, followed later by cell loss in the matrix compartment. However, little is known about how this relates to pathogenesis and pathophysiology. While MRI cannot visualize these striatal compartments directly in humans, differences in relative gradients of afferent cortical connectivity across compartments (weighted toward paralimbic versus sensorimotor cortex, respectively) can be used to infer potential selective loss in vivo. In the current study we evaluated relative connectivity of paralimbic versus sensorimotor cortex with the caudate and putamen in 17 individuals with XDP and 17 matched controls. Although caudate and putamen volumes were reduced in XDP, there were no significant reductions in either "matrix-weighted", or "striosome-weighted" connectivity. In fact, paralimbic connectivity with the putamen was elevated, rather than reduced, in XDP. This was driven most strongly by elevated putamen connectivity with the anterior insula. There was no relationship of these findings to disease duration or striatal volume, suggesting insula and/or paralimbic connectivity in XDP may develop abnormally and/or increase in the years before symptom onset.