Voxel-Based Morphometry and Relaxometry Demonstrate Macro- and Microstructural Damages in Spinocerebellar Ataxia Type 3.

Spinocerebellar ataxia type 3/Machado-Joseph disease (SCA3/MJD) is the most common SCA worldwide and comprises about 70% of SCA patients in Brazil. Magnetic resonance imaging (MRI) sequences have been used to describe microstructural abnormalities in many neurodegenerative diseases and helped to reveal the excessive iron accumulation in many of these conditions. This study aimed to characterize brain changes in gray matter (GM) and white matter (WM), detected by voxel-based morphometry (VBM) and relaxometry in patients with SCA3/MJD. A group of consecutive individuals, older than 18 years of age, with symptomatic and genetically proven SCA3/MJD diagnosed, and a control group, were submitted to clinical evaluation and MRI. The images were analyzed using VBM technique and relaxometry. The global assessment of brain volume by region of interest showed a significant difference in GM between SCA3/MJD and normal controls. VBM was used to locate these volumetric changes and it revealed a noticeable difference in the GM of the cerebellum and the brainstem. The global assessment of the brain by relaxometry also showed a significant difference in the comparison of GM between SCA3/MJD and normal controls, detecting noticeable prolongation of T2 time in the medulla oblongata (p < 0.001) and in the pontine tegmentum (p = 0.009) in SCA3/MJD compared to control group. Our study suggests that SCA3/MJD affects the macrostructure of the cerebellum and brainstem and microstructure of pons and medulla oblongata GM, as already demonstrated in the pathological study.