Typical multiple sclerosis (MS) lesions occur in the brain as well as in the spinal cord. However, two extreme magnetic resonance imaging phenotypes appear occasionally: those with predominantly spinal cord lesions (MS + SL) and those with cerebral lesions and no detectable spinal lesions (MS + CL). We assessed whether morphological differences can be found between these two extreme phenotypes. We examined 19 patients with MS + SL, 18 with MS + CL and 20 controls. All subjects were examined using magnetic resonance imaging, including anatomical and diffusion tensor imaging sequences. Voxel-based morphologic and regions of interest-based analyses and tract-based spatial statistics were performed. Patients also underwent neuropsychological testing. Demographic, clinical and neuropsychological characteristics did not differ between MS + SL and MS + CL patients. Patients with MS + SL showed significantly larger putamen volumes than those with MS + CL which correlated negatively with disability. Compared to controls, only MS + CL revealed clear cortical and deep gray matter atrophy, which correlated with cerebral lesion volume. Additionally, extensive white matter microstructural damage was found only in MS + CL compared to MS + SL and controls in the tract-based spatial statistics. Higher putamen volumes in MS + SL could suggest compensatory mechanisms in this area responsible for motor control. Widely reduced fractional anisotropy values in MS + CL were caused by higher cerebral lesion volume and thus presumably stronger demyelination, which subsequently leads to higher global gray matter atrophy.
Keywords: Multiple sclerosis; Putamen; TBSS; VBM.