ObjectiveFactors that play a role in the selection of surgical approach for acoustic neuromas include patient health and age, size of tumor, hearing status, and location of tumor in the internal auditory canal (IAC) and the cerebellopontine angle. Deep extension into the IAC makes hearing preservation extremely difficult when a retrosigmoid craniotomy is used, and the best approach is a middle fossa subtemporal route. Modern gadolinium-enhanced magnetic resonance imaging (MRI) can be inaccurate in identifying the presence of tumor laterally in the IAC. This may affect the selection of a surgical approach.Study DesignThis study was a retrospective case review.SettingPatients were accrued from a tertiary referral otologic practice.PatientsFrom 1997 through 2000, the authors identified six patients who had undergone acoustic neuroma surgery, had adequate imaging and intraoperative data, and demonstrated a lack of correlation between MRI and intraoperative findings of the lateral IAC.InterventionThe interventions were preoperative MRI of the IAC and surgical resection of an acoustic neuroma.Main Outcome MeasureComparison of MRI and intraoperative findings of the lateral IAC were the main outcome measures.ResultsSix patients demonstrated a lack of correlation between MRI and intraoperative findings of the lateral IAC.ConclusionsGadolinium-enhanced T1-weighted MRI findings of the depth of penetration into the lateral aspect of the IAC do not always correlate with intraoperative findings and thus may have implications in the selection of surgical approaches to acoustic neuromas.