Synchrotron X-ray Fluorescence Reveals Abnormal Metal Distributions in Brain and Spinal Cord in Spinocerebellar Ataxia: A Case Report

For the first time, synchrotron rapid-scanning X-ray fluorescence (RS-XRF) was used to simultaneously localize and quantify iron, copper, and zinc in spinal cord and brain in a case of spinocerebellar ataxia (SCA). In the normal medulla, a previously undescribed copper enrichment was seen associated with spinocerebellar fibers and amiculum olivae. This region was virtually devoid of all metals in the SCA case. Regions with neuronal loss and gliosis in the cerebellar cortex, inferior olivary, and dentate nuclei and areas showing loss of myelinated fibers were also low in all metals in SCA compared to control. In contrast, the ventral columns of the spinal cord that exhibited only moderate myelin pallor had increased metal levels. Iron and zinc were also elevated in the globus pallidus pars externa in SCA relative to control. We hypothesize that metals increase as part of the initial neurodegenerative process, but once degeneration is advanced, the metal levels drop. This implies a role for multiple metals in SCA neurodegeneration, but further study is required to establish a causative role. We suggest that if these findings are generally true of at least some cases of SCA, not only iron but also copper and zinc should be considered as possible therapeutic targets.