Compared with DMD cases and non-neuromuscular disease controls, FCMD cases showed a reduction of total gangliosides, and an abnormal, immature ganglioside pattern in the cerebral gray and white matter. However, GM4, which is only found in myelin and oligodendroglia, and is a unique quantitative marker of myelination, was present in a relatively high percentage in the white matter, which showed frontal lobe micropolygyria and diffuse low density on CT and MR T1-imaging.