Intracranial biomechanics following cortical contusion in live rats

Abstract

Object. The goal of this study was to examine the mechanical properties of living rat intracranial contents and corresponding brain structural alterations following parietal cerebral cortex contusion.Methods. After being anesthetized, young adult rats were subjected to parietal craniotomy followed by cortical contusion using a calibrated weight-drop method. Magnetic resonance imaging was used to visualize the contusion. At the site of contusion, instrumented force-controlled indentation was performed 2 hours to 21 days later on the intact dural surface. The force-deformation (stress-strain) relationship was used to calculate elastic (indentation modulus) and strain changes over time, and constant hold or cyclic stress was used to evaluate viscoelastic deformation. These measurements were followed by histological studies.Results. At contusion sites, the indentation modulus was significantly decreased at 1-3 days and tended to be above control values at 21 days. Multicycle indentation showed that the brain tended to accumulate more strain (an indicator of viscosity) by 1 day after the contusion. Imaging and histological studies showed local edema and hemorrhage at 6 hours to 3 days and accumulation of reactive astrocytes, which began at 3 days and was pronounced by 21 days.Conclusions. The viscoelastic properties of living rat brain change following contusion. Initially, edema and tissue necrosis occur, and the brain becomes less elastic and less viscous. Later, along with undergoing reactive astroglial changes, the brain tends to become stiffer than normal. These quantitative data, which are related to the physical changes in the brain following trauma and which reflect subjective impressions upon palpation, will be useful for understanding emerging diagnostic tools such as magnetic resonance elastography.

Biomechanical simulation of traumatic brain injury in the rat

“…The effective elastic modulus was 100 -600 Pa, depending on the location and indentation depth, and grey matter was stiffer than white mater. More recently, AFM indentation showed that injury softens the brain and spinal cord (Moeendarbary et al, 2017), in agreement with previous investigations (Alfasi et al, 2013;Shafieian et al, 2009). Elastic moduli of the intact cortex were 200-300 Pa. All AFM studies of the rodent brain to date have neglected viscoelastic effects.…”

Dual-porosity poroviscoelasticity and quantitative hydromechanical characterization of the brain tissue with experimental hydrocephalus data

“…The feasibility of using diffusion tensor imaging in in-vivo detection and tracking of these structural changes, both during the progression of hydrocephalus and after shunting surgery, has recently been documented (Eskandari et al, 2014;Hattingen et al, 2010). Also Alfasi et al (2013) studied these structural damages and their effect on the brain tissue's viscoelastic properties. They concluded that factors such as edema and tissue's necrosis weaken the brain's elastic and viscous properties at the early stages of hydrocephalus.…”

Advanced Neuroimaging Role in Traumatic Brain Injury: A Narrative Review

“…With MRE, several studies of preclinical models have indicated its potential usefulness in TBI. The mechanical properties of the brain (as measured by MRE) have been found to change following brain injury in living rat and mice ( Alfasi et al, 2013 ; Boulet et al, 2013 ). Furthermore, using a TBI mouse model, a longitudinal study of MRE demonstrated that the elastic modulus of the injured brain tissue was higher than that of the contralateral hemisphere 1 h after injury ( Feng et al, 2017 ).…”