Does the brain have mechanical compliance?

Excerpt

The terms “intracranial compliance” and “brain compliance” are often used interchangeably in the cerebrospinal fluid (CSF) literature [1, 2]. It is therefore time to clarify what intracranial compliance is and whether brains have compliance. The impetus for this commentary is a sentence I read while reviewing a manuscript; “Intracranial compliance is the ability of the brain to adapt to changes in intracranial volume while maintaining intracranial pressure”. I had to read it twice because compliance has a lot to do with changes in volume and pressure but nothing to do with the ability of the brain to adapt to these changes. The notion behind “brain compliance” is likely related to the perception that the brain is “soft” and therefore it can accommodate a change in volume. The brain is not “soft” in the same way that water is not soft as both are incompressible within the physiological range of pressure changes. The brain material is viscoelastic, it is pliable, it can change its shape upon application of force, it is deformable and its resistance to deformation is termed stiffness [3]. The stiffness of the brain can actually be measured without touching it using MR elastography (MRE) [4] by imaging the propagation of shear waves through the brain caused by mechanical vibrations. Brain MRE is a maturing technique that is being used to map the stiffness of tissues throughout the brain in the healthy and disease states [5]. …