A neuropathological study at autopsy of early onset spinocerebellar ataxia 6

Spinocerebellar ataxia type 6 (SCA6) is a late-onset, autosomal dominantly inherited ataxic disorder, and most previous clinical studies consider SCA6 to be a “pure” cerebellar ataxia. We carried out a detailed pathoanatomical study at autopsy of two patients, brother and sister, with genetically confirmed SCA6. The disease in both patients was early onset and short, which is atypical for SCA6. We observed severe neurodegeneration in the cerebellum, dentate nucleus and olivary nuclei. Both patients showed evidence of synaptic modification in the cerebellar cortex, which morphologically confirmed the existence of retrograde and anterograde trans-synaptic degeneration secondary to the cerebellar cortical lesion. Furthermore, our study shows for the first time that neurodegeneration in SCA6 occurs in the spinal cord. Finally, our postmortem study confirms that SCA6 is not a simple “pure” cerebellar disease, but a complex neurodegenerative condition in which many extracerebellar structures are involved.