• Sean J Nagel, Logan Helland, Royce W Woodroffe, Leonardo A Frizon, Marshall T Holland, Andre G Machado, Satoshi Yamaguchi, George T Gillies, Matthew A Howard, and Saul Wilson.
• Neurological Surgery, Cleveland Clinic, Cleveland, OH, USA.
• Neuromodulation. 2019 Dec 1; 22 (8): 916-929.

IntroductionWe are developing a novel intradural spinal cord stimulator for treatment of neuropathic pain and spasticity. A key feature is the means by which it seals the dura mater to prevent leakage of cerebrospinal fluid (CSF). We have built and employed a test rig that enables evaluation of candidate seal materials.MethodsTo guide the design of the test rig, we reviewed the literature on neurosurgical durotomies. The test rig has a mock durotomy slot with a dural substitute serving as the surrogate dura mater and water as the CSF. The primary experimental goal was to evaluate the effectiveness of candidate gasket materials as seals against CSF leakage in an implanted prototype device, at both normal and super-physiologic pressures. A secondary goal was to measure the transmembrane flows in a representative dural substitute material, to establish its baseline aqueous transport properties.ResultsThe seals prevented leakage of water at the implantation site over periods of ≈ ten days, long enough for the scar tissue to form in the clinical situation. The seals also held at water pressure transients approaching 250 mm Hg. The residual volumetric flux of water through the dura substitute membrane (Durepair®) was δVT /A ≈ 0.24 mm3 /min/cm2 , consistent with expectations for transport through the porous membrane prior to closure and equalization of internal/external pressures.ConclusionsWe have demonstrated the workability of obtaining robust seal against leakage at the implantation site of a novel intradural stimulator using a custom-designed test rig. Extension of the method to in vivo testing in a large animal model will be the next step.© 2019 International Neuromodulation Society.

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