Comparison of computerized tomography and magnetic resonance imaging for the postoperative assessment of residual acoustic tumor.

Ten patients with surgically confirmed residual cerebellopontine angle neuromas, imaged by both computerized tomography (CT) with iodine contrast and magnetic resonance (MR) with and without gadolinium enhancement, are reviewed to identify the strengths and limitations of MR as compared with CT imaging. MR imaging offers superior anatomic resolution in multiple imaging planes without ionizing radiation, but it is expensive and has adverse effects on some patients. CT imaging offers good anatomic resolution, but in only one or two planes. CT is both less expensive and generally well tolerated, but allergy to the iodine contrast is not uncommon. The cases presented demonstrate the adequacy of CT imaging of residual tumor. However, in some cases MR imaging provided important additional detail. MR imaging also demonstrated postoperative changes within the brain stem and cerebellum. In our experience, CT imaging remains a satisfactory, unambiguous approach to the assessment of known postoperative residual cerebellopontine angle neuromas. MR imaging provides superior resolution, however, and should be used when better definition of tumor detail is needed for management decisions or when multiple follow-up scans are anticipated, so that the exposure to ionizing radiation is limited. MR is also useful to investigate postoperative neurologic dysfunction. Postoperative changes and residual tumors are more difficult to interpret on MR than on CT. Guidelines are proposed to help distinguish residual tumor from postoperative changes and scarring.