Positional brain shift (BS), as the physiological sagging of the brain under the effect of gravity, has a magnitude that is comparable to the accuracy of neuronavigational systems. It is a complex interaction of gravity, anatomical boundaries and tissue mesostructure. A comprehensive investigation of such deformation is needed. This study aims to provide a rich set of volumetric measures to infer the pattern of deformation as well as the time evolution of positional BS. Results show that positional BS is a relatively fast process, stabilised in 10 minutes, with local variations strongly dependent on the variability of anatomical structures between different subjects.