Hình 11,5 phương pháp tiếp cận hố sau phiên điều trần bảo quản trong việc loại bỏ schwannoma tiền đình đòi hỏi phải tiếp xúc của meatus thính giác bên trong (mũi tên). Khối u T, F FN, CRN thấp hơn sọ dây thần kinh | Internal Auditory Canal and Cerebellopontine Angle 101 Fig. The posterior fossa approach for hearing preservation in vestibular schwannoma removal requires exposure of the internal auditory meatus arrow . T tumor F FN CRN lower cranial nerves Fig. The canalicular portion of tumor arrow has been dissected from the internal canal with preservation of the facial F and cochlear C nerves Fig. Photomicrograph of an intralabyrinthine cochlear nerve schwannoma T . The endolymphatic hydrops arrows is caused by tumor compression of the ductus reuniens. R Reissner s membrane 102 Chapter 11 Tumor Surgery Fig. Gadolinium-en-hanced MRI demonstrates an intralabyrinthine cochlear schwannoma arrow in a patient with the audiogram in Fig. 11 IAC. In this location the nerve is encountered before tumor dissection is initiated. The results with hearing preservation however are better than with other approaches because the labyrinthine blood supply is remotely located inferiorly in the IAC and can be avoided. Intralabyrinthine Vestibular Cochlear Schwannoma The proliferation of Schwann cell neoplasms may be limited to the bony labyrinth 1 12 22 . These tumors arise from the peripheral vestibular nerve branches after leaving the cribrose portions of the otic capsule and before supplying the vestibular sense organs. In the cochlea they arise from the dendrites of spiral ganglion cells adjacent to the scala tympani Fig. . These tumors are usually limited to the bony labyrinth and are referred to as intralabyrinthine schwannomas. The clinical presentation of the vestibular variety is frequent recurrent vertigo while the cochlear nerve type is associated with sensorineural hearing loss usually in the low frequencies. If an intracanalicular component has been excluded by imaging studies then excision of the intralabyrinthine schwannoma may be accomplished through the middle ear after removal of the promontory. In the past most cases of intralabyrinthine
