In vivo modeling of interstitial pressure in the brain under surgical loadusing finite elements

Current brain deformation models have predominantly reflected solid constit utive relationships generated from empirical ex vivo data and have largely overlooked interstitial hydrodynamic effects. Irt the context of a techniqu e to update images intraoperatively for image-guided neuronavigation, we ha ve developed and quantified the deformation characteristics of a three-dime nsional porous media finite element model of brain brain deformation in viv o. Results have demonstrated at least 75-85 percent predictive capability, but have also indicated that interstitial hydrodynamics are important In th is paper we investigate interstitial pressure transient behavior in brain t issue when subjected to art acute surgical load consistent with neurosurgic al events. Data are presented from three in vivo porcine experiments where subsurface tissue deformation and interhemispheric pressure gradients were measured under conditions of art applied mechanical deformation and then co mpared to calculations with our three-dimensional brain model. Results demo nstrate that porous-media consolidation captures the hydraulic behavior of brain tissue subjected to comparable surgical loads and that the experiment al protocol causes minimal trauma to pot-cine brain tissue. Working values for hydraulic conductivity of white and gray matter are also reported and a n assessment of transient pressure gradient effects with respect to deforma tion is provided. [S0148-0731(00)00804-9].