Superior vestibular neurectomy: a novel transmeatal approach for a denervation of the superior and lateral semicircular canals.

OBJECTIVE: To assess morphologically a transmeatal approach to the lateral and superior ampullary nerves performable under local anesthesia and simultaneously with the existing approach to the singular nerve developed by Gacek during the same operation.
MATERIALS AND METHODS: Eighty halves of human heads preserved with the Thiel method were operated on by an otologist. Two surgical approaches were tested on each specimen, 1 superior and 1 inferior to the tympanic segment of the facial nerve. The 80 specimens were divided into 2 groups. In the first group, the osseous canal of the nerves of the lateral and superior semicircular canal were previously probed and next operated. In the second group, the osseous canal of the nerves were operated prior assessment by dissection. Afterward, all 80 halves underwent computed tomographic investigation to measure the distance between the entrance point of the drill in the medial wall of the tympanic cavity and the osseous canal the ampullary nerves.
RESULTS: Inferior approach to the canal of the nerves could not be done without wide opening of the vestibulum in all 80 specimens. In the superior approach, the nerve could be reached directly in 5 cases, and only via the osseous ampulla of the lateral semicircular canal in 28 cases in the first group. In 7 cases, the nerves could not be reached without damage to the membranous labyrinth. In the second group, the nerve could be reached directly in 2 cases, via the osseous ampulla in 36 cases, and was unreachable in 2 cases. Significantly, distances longer than 3 mm between the surgical access and the nerve were found on the inaccessible cases.
CONCLUSION: A transmeatal approach is possible superiorly but not inferiorly to the facial nerve, although it is necessary to open the osseous ampulla but not the membranous labyrinth in most cases.