Fifty years of brain tissue mechanical testing: from in vitro to in vivo investigations.

Beginning in the 1960s many studies have been performed to investigate the mechanical properties of brain. In this paper we point out the difficulties linked with in vitro experimental protocols as well as the advantages of using recently developed non-invasive in vivo techniques, such as magnetic resonance elastography. Results of in vitro and in vivo work are compared, emphasizing the specificities and disparities of the in vitro as well as the in vivo results. In particular, a detailed discussion of the results obtained from dynamic shear experiments and magnetic resonance elastography is given before arriving at a tentative conclusion on the state of knowledge of the mechanical properties of brain.