Surgical Techniques in Preservation of Facial Nerve in Large & Giant Vestibular Schwannomas

An understanding of the mechanism of formation of arachnoid fold around vestibular schwannoma is crucial in preserving the anatomical integrity of 7th nerve. The author, who has an operative experience of 730 cases of vestibular schwannomas over a period of sixteen and a half years with an operative mortality of less than 1%, describes the technical pearls for preservation of facial nerve. The essential initial step is peeling of the double layer of arachnoid from the posterior tumor surface. After reduction of the tumor volume, continued dissection of the arachnoid fold toward the brainstem can be achieved without opening the arachnoid over the fifth and lower cranial nerves, which are in separate cisterns. The key element in successful vestibular schwannoma is understanding that flattened facial and cochlear nerves do not have a arachnoid separating them from the tumor capsule which is essentially the perineurium of the vestibular nerve from which tumor has grown. If the tumor cannot be dissected from 7th nerve easily, a sub-perineural dissection is advised. Bipolar coagulation over the tumor surface is avoided. The intracanalicular component of the tumor is removed by doing tailored drilling of internal auditory canal. Acoustic neurinoma surgeons should strive to keep anatomical integrity of 7th nerve even in large acoustic tumors. In the context of our new understanding of the subarachnoid origin of vestibular schwannoma based on current publications, the technical nuances of operative management with particular emphasis on extra-sub-perineural dissection is described.