Temporal Bone Pathology of Acoustic Neurinoma (Unilateral and Bilateral) in Relation to the Internal Auditory Canal Surgery

Abstract

Temporal bone pathology of 3 cases with large unilateral acoustic neurinoma (AN) and 2 cases with large bilateral AN (neurofibromatosis 2; NF2) were studied. One case with unilateral AN was diagnosed as neurofibromatosis 1 (NF1). Unilateral AN had distinct borderlines at the fundus in 5 of 12 examination points between tumor tissues and nerve fibers, but only 1 of 12 was distinct around the porus acousticus. Bilateral AN showed no distinct borderlines at the fundus and around the porus acousticus. These findings suggest that clear separation of the VIIth or VIIIth nerve from large tumors is very difficult, especially in cases of bilateral AN. Geniculate ganglion cells of tumor origin on ears were fairly well preserved in 2 cases with unilateral AN and 1 case with bilateral AN. Well preserved geniculate ganglion cells could be dependent on blood supply not from the internal auditory artery.