Conservation of hearing in acoustic schwannoma surgery.

Hearing conservation in acoustic schwannoma surgery is possible in approximately 50% of patients those tumors measure 15 mm or less in size (medial to the porus acusticus) and whose speech discrimination score in the ear with the tumor is 80% or better. The concepts of total tumor removal and maximum sparing of adjacent normal neural tissue are consistent with efforts to retain cochlear function. A retrosigmoid approach is favored over the middle cranial fossa approach because of its superior exposure and less morbidity. An operating table capable of 35 degrees side rotation is used because it allows the majority of patients with acoustic neuromas to be operated on in the horizontal supine position. The posterior lip of the internal auditory canal is removed to within approximately 1.5 mm of the falciform crest. Tumors not extending to the fundus afford an ideal situation for total removal, early identification of the seventh cranial nerve, and preservation of hearing. The carbon dioxide laser is a useful surgical tool with its properties of vaporization, cutting, and coagulation.