Ezer Haim, Banerjee Anirban Deep, Bollam Papireddy, Guthikonda Bharat, Nanda Anil
Department of Neurosurgery, Louisiana State University Health Sciences Center, Shreveport, Louisiana.
J Neurol Surg B Skull Base. 2012 Jun;73(3):175-82. doi: 10.1055/s-0032-1311755.
Objective The superior transvelar approach is used to access pathologies located in the fourth ventricle and brainstem. The surgical path is below the venous structures, through the superior medullary velum. Following splitting the tentorial edge, near the tentorial apex, the superior medullary velum is split in the cerebello-mesencephalic fissure. Using the supracerebellar infratentorial, transtentorial or parietal interhemispheric routes, the superior medullary velum is approached. Splitting this velum provides a detailed view of the fourth ventricle and its floor. Materials and Methods A total of 10 formalin-fixed specimens were dissected in a stepwise manner to simulate the superior transvelar approach to the fourth ventricle. The exposure gained the distance from the craniotomy site and the ease of access was assessed for each of the routes. We also present an illustrative case, operated by the senior author (AN). Results The superior transvelar approach provides access to the entire length of the fourth ventricle floor, from the aqueduct to the obex, when using the parietal interhemispheric route. In addition, this approach provides access to the entire width of the floor of the fourth ventricle; however, this requires retracting the superior cerebellar peduncle. Using the supracerebellar infratentorial route gives a limited exposure of the superior part of the fourth ventricle. The occipital interhemispheric route is a compromise between these two. Conclusion The superior transvelar approach to the fourth ventricle provides a route for approaching the fourth ventricle from above. This approach does not require opening the posterior fossa in the traditional way, and provides a reasonable alternative for accessing the superior fourth ventricle.
目的 经上髓帆入路用于显露位于第四脑室和脑干的病变。手术路径位于静脉结构下方，穿过上髓帆。在小脑幕切迹附近切开小脑幕边缘后，于小脑-中脑裂处切开上髓帆。通过小脑上幕下、经小脑幕或顶叶半球间入路接近上髓帆。切开该帆可提供第四脑室及其底部的详细视野。
材料与方法 共对10个福尔马林固定标本进行逐步解剖，以模拟经上髓帆入路至第四脑室。评估每种入路从开颅部位获得的暴露范围及操作难易程度。我们还展示了由资深作者（AN）实施手术的一个病例。
结果 采用顶叶半球间入路时，经上髓帆入路可显露第四脑室底部从导水管至闩的全长。此外，该入路可显露第四脑室底部的整个宽度；然而，这需要牵拉小脑上脚。采用小脑上幕下入路对第四脑室上部的暴露有限。枕叶半球间入路是这两种入路之间的一种折衷选择。
结论 经上髓帆入路至第四脑室提供了一种从上方接近第四脑室的途径。该入路无需传统方式打开后颅窝，为进入第四脑室上部提供了一种合理选择。
