Residual and recurrent acoustic neuroma in hearing preservation procedures: neuroradiologic and surgical findings.

Magnetic resonance imaging with gadolinium DTPA is currently the most accurate method for detecting small intracanalicular yestibular schwannomas. This imaging modality is not nearly as clear in diagnosis of a small residual or recurrent neuroma after a hearing preservation procedure. This study looked for gadolinium-enhanced MRI images mimicking recurrent lesions in 104 consecutive cases of unilateral acoustic neuroma removed with a hearing preservation technique by the retrosigmoid transmeatal approach. A number of cases with enhancing MRI images in the internal anditory canal were reoperated, permitting the histologic examination of the enhancing tissue. Criteria for the MRI diagnosis of residual-recurrent acoustic neuroma are presented, along with the short-to mid-term rate of "residual-recurrent" tumor.