  Brain swelling is a serious condition associated with an accumulation of
fluid inside the brain that can be caused by trauma, stroke, infection, or
tumors. It increases the pressure inside the skull and reduces blood and oxygen
supply. To relieve the intracranial pressure, neurosurgeons remove part of the
skull and allow the swollen brain to bulge outward, a procedure known as
decompressive craniectomy. Decompressive craniectomy has been preformed for
more than a century; yet, its effects on the swollen brain remain poorly
understood. Here we characterize the deformation, strain, and stretch in
bulging brains using the nonlinear field theories of mechanics. Our study shows
that even small swelling volumes of 28 to 56 ml induce maximum principal
strains in excess of 30%. For radially outward-pointing axons, we observe
maximal normal stretches of 1.3 deep inside the bulge and maximal tangential
stretches of 1.3 around the craniectomy edge. While the stretch magnitude
varies with opening site and swelling region, our study suggests that the
locations of maximum stretch are universally shared amongst all bulging brains.
Our model can inform neurosurgeons and rationalize the shape and position of
the skull opening, with the overall goal to reduce brain damage and improve the
structural and functional outcomes of decompressive craniectomy in trauma
patients.

Tissues and Organs