Iron accumulation and axonal damage of cerebellum in idiopathic cervical dystonia

Postmortem brain study indicated that cerebellar Purkinje cell (PC) loss might be a pathological finding in patients with inherited and idiopathic cervical dystonia (ICD). The analysis of conventional magnetic resonance imaging brain scans failed to yield support for this finding. Previous studies have identified that iron overload can be the consequence of neuron death. The objectives of this study were to investigate iron distribution and demonstrate changes in axons in the cerebellum, providing evidence for PC loss in patients with ICD.

Twenty-eight patients with ICD (20 females) and 28 age- and sex-matched healthy controls were recruited. A spatially unbiased infratentorial template was applied to perform cerebellum optimized quantitative susceptibility mapping and diffusion tensor analysis based on magnetic resonance imaging. Voxel-wise analysis was performed to assess cerebellar tissue magnetic susceptibility and fractional anisotropy (FA) alterations, and the clinical relevance of these findings was investigated in the patients with ICD.

Increased susceptibility values revealed by quantitative susceptibility mapping in the right lobule CrusI, CrusII, VIIb, VIIIa, VIIIb and IX were found in the patients with ICD. A reduced FA value was found across almost all the cerebellum; an FA value of the significant clusters within the right lobule VIIIa significantly correlated with the motor severity of patients with ICD (r = -0.575, p = 0.002).

Our study provided evidence for cerebellar iron overload and axonal damage in patients with ICD, which may indicate PC loss and related axonal changes. These results provide evidence for the neuropathological findings in patients with ICD and further highlight the cerebellar involvement in the pathophysiology of dystonia.