Quantitative synthetic MRI reveals grey matter abnormalities in patients with spinal muscular atrophy types 2 and 3.

Background: Several studies have shown that spinal muscular atrophy (SMA) is not limited to lower motor neurons. This cross-sectional study aimed to quantitatively investigate the gray matter (GM) alterations in patients with SMA types 2 and 3.

Methods: This is a cross-sectional study. T1 and T2 maps that were extracted from synthetic magnetic resonance imaging (SyMRI) were compared between patients with SMA and healthy controls (HC). Between-group comparisons were made between SMA type 2 and type 3. The association between brain regions with significantly altered T1 and T2 values and clinical measurements were evaluated with Pearson correlation analysis.

Results: Compared with HC, patients with SMA showed widespread altered T1 and T2 values in GM, mainly referring to the cerebellum, default mode network, attention and execution control network, and salience network. Negative correlations were found between Hammersmith Functional Motor Scale Expanded (HFMSE) scores and T2 values of the left orbital part of superior frontal gyrus (P=0.013) and the right olfactory cortex (P=0.008) in the patient group.

Conclusions: Altered T1 and T2 values involving multiple GM regions of the brain demonstrate widespread microscopic alterations in patients with SMA, which might provide an idea for quantitative measurement of SMA nerve damage.