Relationship between neurochemical concentrations and neurofunctional measures in late-onset GM2 gangliosidosis

Magnetic resonance spectroscopy (MRS) and functional MRI (fMRI), related through common biophysical bases, provide complementary information about brain function. The link between MRS and fMRI measures is of interest, especially in the ultra-rare, metabolic disease late-onset GM2 gangliosidosis (LOGG). Imaging studies on LOGG have been few and far between, with cerebellar atrophy and neurochemical impairments being the most prominent findings. However, it remains unknown as to how these neurochemical aberrations relate to neurofunctional characteristics. The goal of this study (7 LOGG, 7 age/sex matched controls) was to assess the relationship between MRS concentrations and fMRI measures derived from the same MRS ROI (cerebellum, thalamus, precuneus) in LOGG. To quantify the communication between MRS regions and rest of the brain, we employed graph measures estimated from resting-state fMRI functional connectivity. We found that one such measure, local efficiency, which quantifies the aggregate relationship between a MRS region and rest of the brain, was significantly associated with N-acetylaspartate (NAA) in the cerebellum and thalamus (p<0.05, FDR corrected). Poorer neuronal health, neuronal loss (NAA), and neuroinflammation (myo-inositol) were related to poorer cerebellum-brain communication. Likewise, reduced thalamus-brain communication was also associated with poorer neuronal health and longer disease duration (p=0.002). These findings hint at a model of impaired neurochemical concentrations in these regions, leading to aberrant communication between them and rest of the brain, which may exacerbate disease progression. Future research must replicate these findings in larger cohorts, and further investigate such abnormalities in the cerebellum, thalamus and precuneus in this ultra-rare neurological disease.