A Classification and Microsurgical Strategy to Seal CSF Leaks at the 360° Dural Circumference via a Posterior Approach and Spinal Cord Release in Spontaneous Intracranial Hypotension

Background: Spinal cerebrospinal fluid (CSF) leaks are the cause of spontaneous intracranial hypotension (SIH). Objective: To report the results of a large surgical series and to propose a surgical strategy, stratified on anatomical location of the leak, for sealing all CSF leaks around the 360° circumference of the dura through a single tailored posterior approach. Methods: All consecutive patients undergoing spinal surgery between February 2013 and October 2017 were included. All patients were refractory to conservative treatment and to epidural blood patching and workup had exactly localized the anatomical site of the leak. We used a posterior approach via a tailored hemilaminectomy or interlaminar fenestration and intraoperative electrophysiological monitoring in all cases. To seal the CSF leak either a mere extradural, foraminal, or transdural microsurgical trajectory was chosen. Neurological status was assessed before, at day 1, 30, and 90 after surgery, as well as modified Rankin Scale and working status at 3 months. Results: Forty-seven SIH patients had a neuroradiologically identified spinal CSF leak between the levels C6 and L1. Micorsurgically, we could localize (anterior n = 35, lateral n = 9, foraminal n = 2) and seal all dural tears via a transdural ( n = 28), a direct extradural ( n = 16), or a foraminal ( n = 2) trajectory. The transdural trajectory necessitated cutting the dentate ligament accompanied by elevation and rotation of the spinal cord under continuous neuromonitoring (spinal cord release maneuver, SCRM). No patient experienced a permanent neurological deficit; four patients had transient deficits. We propose an anatomical stratification of CSF leaks into I ventromedial, that is, anterior to the spinal cord, II ventrolateral, lateral and dorsal, and III foraminal. All CSF leaks can be sealed via a single tailored fenestration and a respective transdural (I), direct extradural (II), and foraminal (III) microsurgical approach. Conclusion: With the posterior microsurgical (tailored fenestration) strategy, it is possible to seal all defects around the 360° surface of the dura via three surgical trajectories, that are selected according to the exact anatomical location of the leak. Intraoperative neuromonitoring is mandatory for the SCRM.