Tumor growth and audiometric change in vestibular schwannomas managed conservatively.

OBJECTIVE: To prospectively define the correlation between changes in tumor volume and audiometric function in vestibular schwannomas managed conservatively. STUDY DESIGN: Prospective longitudinal study. METHODS: Twenty-one patients (age range, 15-84 y; mean age, 63.3 y) with newly diagnosed vestibular schwannomas were enrolled between 1994 and 1999 in a protocol at The Ohio State University Hospital (Columbus, OH) to evaluate the correlation between tumor volume and audiometric change during a period of observation. Patients were evaluated yearly by clinical examination, a standardized internal auditory canal magnetic resonance imaging scan with gadolinium contrast for volumetric analysis, and audiometric function testing. Demographic data, historical features, neurofibromatosis type 2 (NF2) status, initial testing results, and serial testing results were recorded. RESULTS: An increase in tumor volume occurred in 14 of the 21 patients (66%). The pattern of volumetric change was found to be extremely variable. Multiple regression analysis revealed significant correlations of changes in tumor volume with changes in pure-tone average and speech discrimination score (P < .0001 and P = .0021, respectively). Change in tumor volume had greater effect on pure-tone average and speech discrimination score in patients initially with class D audiometric function when compared with those initially in class A (P = .0083 and P = .0245, respectively). The presence of NF2 had an independent protective effect against deterioration of the pure-tone average when compared with patients without NF2 (P = .0125). CONCLUSIONS: This study demonstrated a significant correlation between a change in volume and auditory deterioration in vestibular schwannomas being managed with a trial of observation. A given change in tumor volume appeared to have a greater effect on pure-tone average and speech discrimination score as initial auditory classification declined.