Spinocerebellar ataxia type 2 presenting with a tumefactive demyelinating lesion: expanding the extreme neuroradiological spectrum of <i>ATXN2</i> -mediated leukodegeneration

Spinocerebellar ataxia type 2 (SCA2) is an autosomal-dominant neurodegenerative disorder caused by CAG trinucleotide repeat expansion in the ATXN2 gene, classically characterized by progressive cerebellar ataxia, dysarthria, and slow saccadic eye movements. Although white matter degeneration is increasingly recognized as part of SCA2 pathology, macroscopic tumefactive demyelinating lesions have not been well described. We report a 29-year-old woman with rapidly progressive, genetically confirmed SCA2 (56 CAG repeats) exhibiting marked anticipation compared with her affected father. Brain magnetic resonance imaging revealed diffuse cerebellar and cerebral atrophy along with a solitary, large, non-enhancing tumefactive white matter lesion in the left temporoparietal region. Extensive evaluation excluded inflammatory, autoimmune, infectious, and neoplastic etiologies. We propose that this lesion represents an extreme manifestation of ATXN2 -mediated leukodegeneration rather than a coincidental acquired demyelinating disorder. This case expands the neuroradiological and pathophysiological spectrum of SCA2 and provides clinical support for emerging evidence implicating oligodendroglial dysfunction in polyglutamine diseases.