Proton MRS of a child with Sandhoff disease reveals elevated brain hexosamine

Sandhoff disease (gangliosidosis type 0) is a lysosomal storage disorder with a deficiency of hexosaminidases A and B. After an initially normal development the clinical course of affected children is severe and rapidly progressive leading to spastic tetraparesis, epileptic seizures and early death. In a 10-month-old girl with enzymatically established diagnosis of Sandhoff disease MRI of the brain showed signal changes in the periventricular white matter, pyramidal tract, basal ganglia, and cerebellar hemispheres. Proton MR spectroscopy (MRS) at the age of 13 months revealed a reduction of total N-acetylaspartate (neuroaxonal marker) as well as strongly elevated inositol (glial marker) in white matter, gray matter, and basal ganglia. A new resonance at 2.07 ppm was detected in all regions and ascribed to N-acetylhexosamine with highest concentrations in white matter and thalamus. While conventional MRS findings are in line with neuroaxaonal damage and pronounced astrocytosis, the observation of N-acetylhexosamine appears as a specific marker of Sandhoff disease indicating accumulation of hexosamine-containing oligosaccharides. This interpretation is supported by a recent in vitro MRS study of a Sandhoff mouse model. In conclusion, proton MRS of cerebral metabolites offers specific insights into the pathopysiologic processes of children with Sandhoff disease and may prove to represent another disease specific MRS pattern of the brain.