IC-P1-011: Patterns of cerebral perfusion in 3 clinical behavioral variants of frontotemporal dementia

Abstract

Behavioral variant frontotemporal dementia (bvFTD) can be subdivided into typical bvFTD characterized by behavioral and personality changes, and those with motor neuron disease (FTD-MND). We have identified a subset of bvFTD patients in which features of typical bvFTD overlap with those of dementia with Lewy bodies (FTD-DLB) such that hallucinations and Parkinsonism are also presenting features; MND is not observed clinically. We compared brain perfusion patterns in 4 bvFTD, 4 FTD-MND and 5 FTD-DLB patients compared to 19 normal controls. All 13 patients completed a single photon emission computer tomography (SPECT) study using the radioligand 99mTc-Ethyl cysteinate dimer. Individual SPECT studies were spatially warped to a standard SPECT template (MNI SPECT template) using Statistical Parametric Mapping (SPM2). The result was then masked and smoothed by convolution with an isotropic Gaussian Kernel of 16mm. Group analysis was performed by statistically comparing each group's processed images for significant regions of hypoperfusion against the control group, using SPM. Results were corrected for family-wise error and a cluster extent of 125 contiguous voxels was applied – deemed consistent with the minimum resolution of SPECT imaging. The resultant t-statistics data were transformed in the form of 3D statistical maps and were displayed on the standard T1 MRI template provided by SPM. Average time of disease onset to SPECT was: 1.6 typical bvFTD, 1.5 FTD-MND, and 3 years FTD-DLB. In the typical bvFTD group there was bilateral frontal lobe involvement without striatal involvement. In the FTD-MND group, cortical perfusion changes were similar to typical bvFTD, but there was also striatal hypoperfusion changes not seen in typical bvFTD. Those with FTD-DLB, however had predominantly striatal hypoperfusion with moderate frontotempoal involvment. In this study of three different clinical bvFTD subgroups we found three different patters of hypoperfusion on SPECT scan. These findings suggest that varying involvement of frontotemporal cortex and striatal nuclei may be associated with different presenting features of bvFTD. Given our small sample size, further work is needed to confirm FTD-DLB as a subtype of bvFTD, as well as the association of the three phenotypes with the three patterns of hypoperfusion.