A multimodal MRI investigation of the subventricular zone in mild cognitive impairment and Alzheimer's disease patients

The subventricular zone (SVZ) is a region that lies immediately beneath the ependymal layer on the lateral wall of the lateral ventricles, and is separated from the caudate nucleus by a layer of myelin. It contains multipotent neural stem cells. The aim of this study was to investigate the tissue around the SVZ, with the hypothesis that multimodal MRI is able to highlight the progressive disruption of tissue caused by the neurodegenerative disease in this area. We combined volumetric and diffusion tensor (DTI) imaging using a 3 T imager in a cross-sectional study including 30 patients with amnestic-mild cognitive impairment (a-MCI), 30 patients with Alzheimer's disease (AD) and 30 age- and gender-matched healthy controls (HC). Our data indicate that mean diffusivity (MD) values increase continuously from HC through a-MCI to AD in the bilateral SVZ, where most of the proliferating stem cells in the adult brain are located. This result was specific for the SVZ and could not be observed in other periventricular areas. Multimodal MRI, being able to highlight structural changes of microscopic tissue in humans in vivo, could represent a precious tool to complement histological studies of neurogenesis.