Microscopic Anatomy Of The Central Skull Base Related Structures

Central skull base anatomy is complex and skull base region is of particular concernin clinical neurosurgery. In this study, we observed the area using the surgical microscopeand made related research.Objective: To study the anatomy of the central skull base and provide detailedanatomical information for the central skull base tumor surgery.Methods: We observed the central skull base bone structure, neural and vascularpathways and adjacent structures traveling relationships in the formalin-fixed, coloredlatex perfusion adult cadavers heads through surgical microscope, and usedthe histochemical techniques to describe the relationship among dura, nerves and bloodvessels.Results: The anteroposterior diameter and transverse diameter of the sella is13.79±4.61mm and14.65±5.28mm, respectively. The distance between both sides of the anteriorclinoid process is25.63±2.51mm. The distance between both sides of the posteriorclinoid process is17.02±3.09mm. Petrous ridge length is46.92±3.51mm, parallel to thehorizontal petrous internal carotid artery segment (distance of9.91±1.65mm). The clivusarea contains Ⅰ area, Ⅱ area, Ⅲ area and Ⅳ area. The clivus length is45.31±11.38mm. The pituitary surface of the central skull base has two membranous structures,the inner membrane is called the pituitary lamina propria that is closely with pituitary, deepwithin the gland parenchyma and difficult to separate; while outer appears as a continuousfiber membrane by the histochemical staining, is an extension of the saddle diaphragmdura, surrounding the pituitary, formation the anterior, posterior, inferior and side walls,and called capsule of pituitary. Middle cranial fossa dura mater have inner and outerlayers, and form the space between two layers. This is called parasellar space. Parasellarspace is separated by nervous membrane composed of neural structures, nerve sheaths andmembranous connective tissue. The nervous membrane separated parasellar space into outer gap of dura mater and inside the cavernous sinus. The medial wall and lateral wall ofthe cavernous sinus is capsule of pituitary and the nervous membrane, respectively. In thepetroclival area of central skull base, we can locate the internal acoustic meatus withbisecting line of the angle between the arcuate eminence extension line and the greaterpetrosal nerve. A triangle, formed by the medial lip of the internal acoustic meatus, thegeniculate ganglion and the midpoint between geniculate ganglion and the foramenspinosum, is proposed to precisely locate cochlea.Conclusion: Through this study, we mastered the features of central skull basemembrane structure and the pathways of the cranial nerves and major blood vessels. So wecan take advantage of the natural barrier membrane structure to remove the tumor whileprotecting the nerves and blood vessels. Meanwhile we are familiar with the location andthe surrounding microdissection relationship of the petrous bone. Through grindingthe petrous bone in addition to the maximum, we can expand surgical field areas of thepetrous tip, cerebellopontine angle and the slope of the saddle area to reduce brain stretchand reduce the incidence of complications.