Magnetic resonance imaging of acoustic neuromas: pitfalls and differential diagnosis.

A total of 162 patients with suspected acoustic neuromas underwent MR imaging at 1.5 T. All patients were injected with Gd DTPA or DOTA. In 72 patients, uni- or bilateral acoustic neuromas were detected. 18 cases were equivocal: In 9 cases, contrast enhancement was due to other tumors (5 meningiomas, 2 metastases, 1 hemangioma). In 1 case, misinterpretation resulted from partial volume effects with the petrous bone marrow. In one patient, previously operated on, increased signal was due to postoperative fat graft. Four hypersignals were due to intracanalicular venous or meningeal enhancement. Three cases are still equivocal. Most of the diagnostic problems may be obviated by precontrast MR imaging, multidimensional 3-mm sections, and fast imaging.