Correlation of ventricular asymmetry with metabolic asymmetry in frontotemporal dementia

The clinical presentation of frontotemporal dementia (FTD) is often asymmetrical in terms of both its clinical features and atrophy on MRI. Asymmetry in the lateral ventricle size on structural neuroimaging in FTD patients may have clinical significance. However, this has not been systematically investigated yet. This study compares the ventricular asymmetry seen on MRI with that of the asymmetric glucose metabolism using FDG-PET in patients with FTD.

Nineteen FTD patients who underwent both brain MRI and FDG-PET were retrospectively selected. As control groups, 23 and 11 age and sex-matched healthy normal subjects underwent either brain MRI or FDG-PET, respectively. The ventricular asymmetry index (VAI) was obtained in two ways: by visual rating (VAI-V) and by measuring the lateral ventricular volumes (VAI-ROI). The hemispheric asymmetry of the glucose metabolism on FDG-PET (MAI) was assessed in three ways: 1) by visual rating (MAI-V), 2) by counting the FDG activity of each hemisphere on normalized and smoothed PET images (MAI-ROI) and 3) by counting the number of voxels with significant hypometabolism based on statistical parametric mapping results (MAI-SPM).

The VAIs on MRI (VAI-V and VAI-ROI) were highly correlated, as were the MAIs (MAI-V, MAI-ROI, and MAI-SPM) on FDG-PET. More importantly, the VAIs on MRI and the MAIs on FDG-PET showed high correlation.

Ventricular asymmetry in FTD patients was common (78.9%) and there was a high correlation between the ventricular structural asymmetry and the hemispheric metabolic asymmetry. Therefore, it would be reasonable to interpret that the hemisphere with larger ventricle on MRI in FTD patients is undergoing a more active degenerative process.