There are some reports of cochlear fossa enhancement at MR evaluation of vestibular schwanomma showed poor outcome after hearing preservation operation.

     So we evaluated the outcome of hearing preservation after gamma knife radiosurgery for vestibular schwannoma which showed cochlear fossa enhancement on MR image.

     Of the 6168 GKSs performed between May 1992 and September 2011, 504 procedures were undertaken to treat vestibular schwannoma.

     The inclusion criteria is as followed; hearing-preserved (PTA<50dB, speech discrimination>50%) patients with cochlear fosa enhanced vestibular schwannoma before GKS, who could be followed up more than 2 years, and who were treated with only GKS. We analyzed these patients’s hearing status after GKS.

     Nineteen patients (11 men, 8 women; age range, 26-68 years; mean age, 48.8) were included. The mean tumor volume was1.87cm3 (range, 0.134-9.4cm3) and mean marginal dose 12 (range, 12-13Gy) was prescribed. The exposed dose for cochlear was less than 7Gy. All tumors were controlled and 11 patients (58%) still remained in preserved hearing state during follow up period.

     This was a retrospective study.

     GKS could be positioned for the first line treatment modality of hearing preserved vestibular schwannoma patient who showed cochlear fossa enhancement on MR image.

     The anatomic configuration of a vestibular schwannoma is important for management and therapeutic decisions.