In vivo microstructural white matter changes in early spinocerebellar ataxia 2

Objective: White matter (WM) integrity of Spinocerebellar ataxia 2 (SCA2) is poorly understood, more so in the early stages of SCA2. In this study, we evaluated the microstructural integrity of the WM tracts with an emphasis on the nature of in vivo pathological involvement in early SCA2.

Materials and methods: We evaluated the MRI images of 26 genetically proven SCA2 patients with disease duration <5 years and 24 age- and gender-matched healthy controls using tract-based spatial statistics (TBSS) to identify the WM tract changes and their clinico-genetic correlates (age at onset, duration of disease, ataxia severity and CAG repeat length) using standard methodology.

Results: The mean age at onset and duration of disease were 28.7 ± 8.51 years and 3.5 ± 0.69 months, respectively. The mean CAG repeat length was 42.5 ± 4.6, and the ataxia severity score was 16.1 ± 4.9. Altered DTI scalars signifying degeneration was present in the bilateral anterior thalamic radiation (ATR), corticospinal tract (CST), inferior fronto-occipital fasciculus (IFOF), superior and inferior longitudinal fasciculus (SLF and ILF), uncinate fasciculus (UF), cingulum, corpus callosum (CC), forceps major and forceps minor (corrected p < .05). DTI scalars representing demyelination was seen in the superior cerebellar peduncle (SCP) and cerebellar WM. There was a significant correlation of SARA score with axial diffusivity of the bilateral cingulum, ATR, CST, forceps minor, IFOF, ILF, SLF and SCP on the right side (corrected p < .05).

Conclusion: Extensive WM involvement is present in early SCA2. The DTI scalars indicate degeneration and demyelination and may have clinical implications.