Necrotizing (malignant) external otitis: prospective comparison of CT and MR imaging in diagnosis and follow-up.

PURPOSE: To compare computed tomography (CT) and magnetic resonance (MR) imaging in the diagnosis and follow-up of necrotizing external otitis.

MATERIALS AND METHODS: CT and MR imaging were performed in seven patients at diagnosis and at 6 and 12 months after initiation of therapy. Imaging findings were compared and correlated with the clinical course of the disease.

RESULTS: Cortical bone erosion was best seen on CT scans (n = 5 vs n = 0 on MR images) and failed to normalize with cure. Subtemporal soft-tissue abnormalities (n = 7 with both modalities) were better appreciated with MR imaging and had low signal intensity on T1- and T2-weighted images. Soft-tissue changes improved but did not disappear completely with treatment.

CONCLUSION: CT is preferred at initial diagnosis, as small cortical erosions are better seen. Either modality can be used to follow up soft-tissue evolution. MR imaging may be better for evaluation and follow-up of meningeal enhancement and changes within the osseous medullary cavity.