CAG repeat length does not associate with the rate of cerebellar degeneration in spinocerebellar ataxia type 3

• Main Authors: Shang-Ran Huang, Yu-Te Wu, Chii-Wen Jao, Bing-Wen Soong, Jiing-Feng Lirng, Hsiu-Mei Wu, Po-Shan Wang
• Format: Article
• Language: English
• Published: Elsevier 2017-01-01
• Series: NeuroImage: Clinical
• Subjects: Brain connectivity; Fractal dimension; Magnetic resonance imaging; Magnetic resonance spectroscopy; NAA; SCA3
• Online Access: http://www.sciencedirect.com/science/article/pii/S2213158216302133

This cross-sectional study investigated the correlation between the CAG repeat length and the degeneration of cerebellum in spinocerebellar ataxia type 3 (SCA3) patients based on neuroimaging approaches. Forty SCA3 patients were recruited and classified into two subgroups according to their CAG repeat lengths (≥74 and <74). We measured each patient's Scale for the Assessment and Rating of Ataxia (SARA) score, N-acetylaspartate (NAA)/creatine (Cr) ratios based on magnetic resonance spectroscopy (MRS), and 3-dimensional fractal dimension (3D-FD) values derived from magnetic resonance imaging (MRI) results. Furthermore, the 3D-FD values were used to construct structural covariance networks based on graph theoretical analysis. The results revealed that SCA3 patients with a longer CAG repeat length demonstrated earlier disease onset. However, the CAG repeat length did not significantly correlate with their SARA scores, cerebellar NAA/Cr ratios or cerebellar 3D-FD values. Network dissociation between cerebellar regions and parietal-occipital regions was found in SCA3 patients with CAG ≥ 74, but not in those with CAG < 74. In conclusion, the CAG repeat length is uncorrelated with the change of SARA score, cerebellar function and cerebellar structure in SCA3. Nevertheless, a longer CAG repeat length may indicate early structural covariance network dissociation.