The Role of the Pia Mater in Controlling Brain and Spinal Cord Intraparenchymal Pressure Daniel Harwell MD; Justin Louis Gibson; Richard D. Fessler MD; Jeffrey R. Holtz P.A.-C.; David B. Pettigrew MS PhD; Charles Kuntz, IV MD Department of Neurosurgery, University of Cincinnati and The Mayfield Clinic

Introduction Conclusions Figure 2 Several multicenter randomized control trials have shown that decompression with The simulated edema model has durotomy/duroplasty significantly differential effects on brain and decreases intracranial pressure (ICP), spinal cord IPP. Brain IPP increased improving mortality. Currently, only slightly, consistent with the decompressive craniectomy combined with Figure 1 augmentative duraplasty is widely model that increased intracranial performed and is recommended by most pressure is primarily due to authors. However, there is a paucity of evidence regarding the effectiveness of constraints imposed by the cranium decompression of the spinal cord by and dura mater. In contrast, spinal Peak IPP, Final IPP after 5 days, Post- meningoplasty. cord IPP increased substantially. piotomy IPP. Key: left frontal (FL), right Piotomy immediately and frontal (FR), left parietal (PL), right parietal Methods (PR) lobes. Cervical (C) and thoracic (T) dramatically reduced spinal cord The supratentorial brain and spinal cord spinal cord. Bars: mean + standard were carefully removed from four fresh IPP. These data are consistent with deviation. * indicates statistical significance cadavers. The dura and arachnoid mater the hypothesis that intramedullary compared with FL, FR, PL, and PR peak investments were removed. ICP monitors IPP. were placed bilaterally in the frontal and pressure is primarily due to An example of one representative parietal lobes, as well as the cervical and constraints imposed by the pia preparation at baseline (A) and after (B) 5 Figure 3 thoracic spinal cord. The specimens were mater. Conversely, we hypothesize days of submersion in a hypotonic solution. then submerged in a hypotonic solution Note the sulcal effacement as well as the that the brain sulci permit the pia- and intraparenchymal pressures were generalized swelling of the brain. Focal monitored over 5 days. After 5 days, a invested brain to better herniations are seen in the spinal cord. complete dorsal midline piotomy was accommodate edema without made on the spinal cord and the final pressures were recorded. significant increases in IPP.

Results Learning Objectives Both the brains and spinal cords showed By the conclusion of this session, marked swelling. Brain and spinal cord IPP in cervical and thoracic spinal cord participants should be able to 1) both increased in weight. IPP significantly following piotomy. Bars indicate mean + increased in both brain and spinal cord. Discuss a novel method for standard deviation (mm Hg). * indicates The IPP increase within the spinal cord was modeling neural edema. 2) Describe statistical significance compared with final substantially greater (averages: all four IPP after 5 days. lobes = 4.0 mm Hg; cervical = 73.7 mm the contribution of the pia mater to Hg; thoracic = 49.3 mm Hg). After spinal cord intraparenchymal piotomy, cervical and thoracic spinal cord pressure. 3) Understand how IPP decreased immediately (avg. post- piotomy IPP = 9.7 and 10.3, respectively). piotomy can ameliorate IPP in this model.