Putaminal alteration in multiple sclerosis patients with spinal cord lesions

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.