• Daniel M Harwell, Justin L Gibson, Richard David Fessler, Jeffrey Holtz, David B Pettigrew, and Charles Kuntz.
• *The UC Neuroscience Institute: Department of Neurosurgery, University of Cincinnati College of Medicine, Mayfield Clinic and Spine Institute †Department of Medical Education, University of Cincinnati College of Medicine, OH.
• Spine. 2016 May 1; 41 (9): E524-9.

Study DesignIntraparenchymal pressure (IPP) measurements in an in vitro cadaveric model of CNS edema.ObjectiveTo assess the contribution of pia mater to IPP and the effect of piotomy.Summary Of Background DataMulticenter randomized control trials have shown that decompression with durotomy/duroplasty significantly decreases intracranial pressure (ICP). There is a paucity of evidence regarding the effectiveness of decompression of the spinal cord by piotomy.MethodsThe supratentorial brain and spinal cord were removed from six fresh cadavers. Dura and arachnoid mater were removed. ICP monitors were placed bilaterally in the frontal and parietal lobes, and centrally in the cervical and thoracic spinal cord. To simulate edema, specimens were submerged in hypotonic solution. IPP was recorded for 5 days. A complete dorsal midline piotomy was performed on the spinal cord and resulting IPP was recorded.ResultsBrain and spinal cord both increased in weight. IPP significantly increased in both brain and spinal cord. The IPP increase within the spinal cord was substantially greater (averages: all four lobes = 4.0 mm Hg; cervical = 73.7 mm Hg; thoracic = 49.3 mm Hg). After piotomy, cervical and thoracic spinal cord IPP decreased immediately (avg. postpiotomy IPP = 9.7 and 10.3, respectively).ConclusionThere were differential effects on brain and spinal cord IPP. Brain IPP increased only slightly, possibly because of the absence of the cranium and dura mater. In contrast, spinal cord IPP increased substantially even in the absence of the laminae, dura, and arachnoid mater. Piotomy immediately and dramatically reduced spinal cord IPP. These data are consistent with the hypothesis that spinal cord IPP is primarily dependent on constraints imposed by the pia mater. Conversely, in the absence of the cranium and dura mater, the sulci may permit the pia-invested brain to better accommodate edema without significant increases in IPP.Level Of EvidenceN/A.

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