Frontotemporal dementia as a neural system disease

Some brain structures atrophic in frontotemporal dementia (FTD) belong to the rostral limbic system (RLS), that regulates context-dependent behaviors after evaluation of the motivational content of stimuli. The clinical manifestations of FTD are consistent with its impairment. Aim of this study was to assess whole brain morphology in FTD using magnetic resonance imaging (MRI) and voxel-based morphometry with statistic parametric mapping (SPM99) to test the hypothesis that the RLS might be specifically targeted by FTD. Nine FTD patients and 26 healthy controls underwent high resolution 3D MRI. SPM99 performed (a) spatial normalization to a customized template, (b) segmentation, (c) smoothing, (d) voxel-by-voxel comparison of gray matter between cases and controls. P was set at 0.05 corrected for multiple comparisons. All but one regions of the RLS (the periaqueductal gray) were atrophic in FTD. At P<0.001 uncorrected also the periaqueductal gray was atrophic. Atrophy outside the RLS was confined to a few voxels in the frontal and temporal gyri. FTD might be a neural-system disease where the RLS is predominantly damaged.