Combined Supra-and Infra-tentorial Surgical Keyhole Approach To Petroclival Region:microanatomy

ObjectiveTo study the microanatomy of combined supra-and infra-tentorial surgical keyholeapproach to petroclival region,and investigate the application value ofneuroendoscopy.MethodsSubtemporal and suboccipito-retrosigmoid sinus keyhole approaches were modifiedrespectively in20sides of adult wet cadaveric heads injected with silicone. Theexposure to petroclival region was examined under microscope and potential blindangles were probed with neuroendoscopy. The suitable operating zone were labelledunder neuronavigation and then three-dimensional reconstructed on CT scan.Relateddata estimates were carried on with the aid of neuronavigation.Results①A good vision to interpeduncular cistern, ipsilateral ambient cistern, the upper partof the prepontine cistern，parasella, suprasellar regions and the middle cranial fossacould be obtained via subtemporal keyhole approach. Incision of the tentoriumexposed the inferior part of prepontine cistern and ambient cistern. A way to thecerebellopontine angle cistern could not be acquired due to the blocking effect ofpetrous apex. The volume mean of exposing to petroclival region was3.38cm~3.②Suboccipito-retrosigmoid sinus keyhole approach has a good view tocerebellopontine angel cistern, posterior ambient cistern and prepontine cistern, andits exposed volume mean was2.27cm~3. The space from the posterior part of the cavernous sinus to the opening of Meckel’s cave could not be obtained due to thesheltering action from petrous bone.③The space from the posterior part of the cavernous sinus to the opening of Meckel’scave was still a blind angle for combined approach and its volume mean was0.89cm~3,which could be exposed with neuroendoscopy.Conclusion①The two approaches mentioned above have good complementation.②The space from the posterior part of the cavernous sinus to the opening of Meckel’scave is still a blind angel and it covers space small.③The blind angel could be exposed under neuroendoscopy, on which the operationfeasibility still needs to be discussed due to small space and complicated anatomy.④Auxiliary therapies,such as gamma knife, may be safe and effective for small tumorremnants.