OBJECTIVE: Information on cochlear MRI signal change following vestibular schwannoma (VS) surgery by the retrolabyrinthine approach (RLA) is nonexisting, and information using the translabyrinthine approach (TLA) is scarce. We aimed to evaluate cochlear MRI fluid signal in patients with a unilateral VS, before and after surgery by the RLA or the TLA, that can have clinical importance for subsequent cochlear implantation feasibility.

STUDY DESIGN: Retrospective cohort study.

SETTING: University hospital.

PATIENTS: One hundred one patients with a unilateral VS.

INTERVENTION: VS resection by the TLA or the RLA. Pre- and postoperative T2-weighted MRI.

MAIN OUTCOME MEASURE: Cochlear signal change using a semiquantitative system for grading cochlear asymmetry, with grades ranging from 1 (normal fluid signal both sides) to 4 (no fluid signal one side).

RESULTS: Seventy-four patients were operated by the TLA and 27 by the RLA. The number of cochleas with grade 3 and 4 asymmetries postoperative was significantly higher than preoperative. The postoperative proportions of grade 1 (TLA 20%, RLA 56%) and grade 2-4 asymmetry (TLA 80%, RLA 44%) were significantly different between the two groups. In the TLA group, 46 patients (62%) demonstrated an increased asymmetry postoperatively, as compared with three patients (11%) in the RLA group.

CONCLUSIONS: Postoperative decrease of cochlear MRI fluid signal is more likely to occur after translabyrinthine surgery (occurring in 62%), as compared with retrolabyrinthine surgery (occurring in 11%). The decrease of cochlear signal may be due to compromised vascularity or fibrosis.