Perfusion-mechanics coupling of the hippocampus

Abstract

The hippocampus is a highly scrutinized brain structure due to its entanglement in multiple neuropathologies and vulnerability to metabolic insults. This study aims to non-invasively assess the perfusion-mechanics relationship of the hippocampus in the healthy brain across magnetic resonance imaging sequences and magnetic field strengths. In total, 17 subjects (aged 22-35, 7 males/10 females) were scanned with magnetic resonance elastography and arterial spin labelling acquisitions at 3T and 7T in a baseline physiological state. No significant differences in perfusion or stiffness were observed across magnetic field strengths or acquisitions. The hippocampus had the highest vascularity within the deep grey matter, followed closely by the caudate nucleus and putamen. We discovered a positive perfusion-mechanics correlation in the hippocampus across both 3T and 7T groups, with a highly significant correlation overall (R = 0.71, p = 0.0019), which was not observed in the caudate nucleus, a similarly vascular region. Furthermore, we supported our hypothesis that increased perfusion in the hippocampus would lead to greater pulsatile displacement in a small cohort (n = 10). Given that the hippocampus is an exceptionally vulnerable structure, with perfusion deficits often seen in diseases related to learning and memory, our results suggest a unique mechanistic link between metabolic health and stiffness biomarkers in this key region for the first time.

Keywords: MR elastography; brain mechanics; brain pulsatility; hippocampus; neuroimaging; perfusion.