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 vestibular schwan nomas. This imaging modality is not nearly as clear in diagnosis of a small residual or recurrent neuroma after a hearing preservation proce dure. This study looked for gadolinium-enhanced MRI images mimicking r ecurrent lesions in 104 consecutive cases of unilateral acoustic neuro ma removed with a hearing preservation technique by the retrosigmoid t ransmeatal approach. A number of cases with enhancing MRI images in th e internal auditory canal were reoperated, permitting the histologic e xamination of the enhancing tissue. Criteria for the MRI diagnosis of residual-recurrent acoustic neuroma are presented, along with the shor t-to mid-term rate of ''residual-recurrent'' tumor.