Decompressive craniectomy causes a significant strain increase in axonal fiber tracts

Decompressive craniectomy (DC) allows for the expansion of a swollen brain outside the skull and has the potential to reduce intracranial pressure. However, the stretching of axons may contribute to an unfavorable outcome in patients treated with DC. In this study, we present a method for quantifying and visualizing axonal fiber deformation during both the pre-craniectomy and post-craniectomy periods to provide more insight into the mechanical effects of this treatment on axonal fibers. The deformation of the brain tissue in the form of a Lagrangian finite strain tensor for the entire brain was obtained by a non-linear image registration method based on the CT scanning data sets of the patient. Axonal fiber tracts were extracted from diffusion-weighted images. Based on the calculated brain tissue strain tensor and the observed axonal fiber tracts, the deformation of axonal fiber tracts in the form of a first principal strain, axonal strain and axonal shear strain were quantified. The greatest axonal fiber displacement was predominantly located in the treated region of the craniectomy, accompanied by a large axonal deformation close to the skull edge of the craniectomy. The distortion (stretching or shearing) of axonal fibers in the treated area of the craniectomy may influence the axonal fibers in such a way that neurochemical events are disrupted. A quantitative model may clarify some of the potential problems with this treatment.