The Endoscopic Anatomy Of Foramen Magnum Through Transoral Approach

Object:Foramen magnum region contains lower clivus,anterior margin of foramen magnum and atlas-axis. The lesions in this area is difficult to deal with since the region is adjacent to the brainstem, posterior groups nerve,vertebral artery and other important structures.Operation here is a major challenge of neurosurgeons. With the development of head and neck surgery,there have been some clinical reports and microscopic anatomy reports about the surgical approach to this region. And in the recent years,endoscopic technology is playing an increasing role in the development of modern surgery, especially in the application of neurosurgery. The purpose of this study is to determine the differences between endoscopic surgery and microsurgery, and provide anatomical knowledges for endoscopic transoral approach tocraniocervical junction, especially brainstem anterolateral region. We can assess is it better to undergo surgeries in the treatment of diseases located in head and identify some relevant surgical signs.Methods:10dry skull specimens were used to observe the variation of the partial skull base structure position, and measure the relevant anatomical data. Choose other10formalin-fixed adult Han cadaver specimens which were perfused red latex through the internal carotid artery, vertebral artery and jugular vein pressure.5cases of the10were performed simulated operation as endoscopic transoral surgery, and the other five cases were compared with transoral approach under the microscope to this region.Results:1.10dry skull specimens were used to observe their anatomical characteristics in foramen magnum with transoral approach and establish relevant operation signs. Then measure the important anatomical structures related to the surgical approach including clivus exposure range, distance between both sides of occipital condyles, hypoglossal canals and jugular foramens.The final data were taken as the average of three times measured values,and the results were presented as mean (minimum-maximum).2.Five fresh cadaveric heads with neck were used to be performed with transoral neuroendscopy surgery. The we studied anatomic structures of epidural area and ventral side of subdural area. We then dissect the body zone-by-zone,fixed the cadaver cadaver on the holder,cut off the mandible.Secondly, we use the declinator to retract the mouth,cut the tissue along the midline(avoiding the uvula),reveal the posterior pharyngeal fully. Finally,we can observe the anatomy of the craniocervical junction structure clear.3. Inserted into the oral endoscopy can be observed in the oropharynx, the incision posterior pharyngeal soft tissue can see the the prevertebral muscles-head longus and the longus completely cut on both sides of the posterior pharyngeal wall and free retractormany structures of this zone can be observed:the leading edge of the the pharyngeal tubercle lower slope, the foramen magnum, the anterior arch of the atlas, atlas before nodules, grinding visible addition to the anterior arch of the atlas odontoid process, theseare endoscopic surgery operation bony landmarks. An appropriate bone window open in accordance with the slope the size of the "security zone"(20cm*15cm), and cut the dura mater and re-insert the hard endoscopic observed subdural anatomical structures, you can see the pool and cerebellum of myeloid forebay, before the bridge cistern, the vertebral artery in the brain pool to go up the line, until the vertebrobasilar sulcus. Cisterna magna, and myeloid former pool can see the posterior inferior cerebellar artery and anterior spinal artery originated from the vertebral artery, respectively; here you can see the hypoglossal nerve and abducent nerve running; running along the anterior inferior cerebellar artery, can meet the auditory nerve aggregation hear inward direction. With a30-degree artery P1segment penetration after endoscopy in this area you can also see the basilar artery and brain perforated substance, before the surgery area outside of the posterior communicating artery confluence brain artery can also see the mammillary bodies and gray knot section, oculomotor and other anatomical structures.