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

Abstract

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.

Diffusion MR Imaging Features of Skull Base Osteomyelitis Compared with Skull Base Malignancy

“…29 In a study evaluating the CT and MR imaging appearances of necrotizing otitis externa, the authors reported relatively low T2 signal intensity of the abnormal soft tissues beneath the skull base and concluded that the histopathologic characteristics of the disease with a denser matrix and associated fibrosis would explain the relative decrease of T2 signal intensity. 17 Indeed the histopathologic evaluation of the presented patients with SBO revealed fibrosis accompanying chronic inflammation in all patients, which may also explain our observation of a relative decrease of ADC values in SBO relative to the normal soft tissue of the skull base.…”

“…[14][15][16] The typical radiologic changes in SBO include hypointensity of the clival bone marrow signal intensity on T1-weighted images, infiltration and obliteration of the parapharyngeal fat planes, decreased T1 signal intensity, and enhancement within the soft tissues beneath the skull base and infiltration of the retrocondylar fat (as illustrated in Fig 3). 5,8,9,17 However, for the inexperienced reader, the appearance of the soft tissues (especially on T1-weighted images) and accompanying bone marrow changes may suggest a skull base malignancy such as advanced NPC, metastatic disease, or lymphoma. [5][6][7][8] We, therefore, sought to evaluate the value of DWI as a possible technique to assist in the differential diagnosis.…”

Single Photon Emission Computed Tomography/Computed Tomography (SPECT/CT) of the Skull in Necrotizing Otitis Externa: Comparison with Planar Bone Scintigraphy, SPECT and CT

“…Due to its superior contrast resolution, MRI is the imaging technique of choice in assessing soft-tissue involvement in NOE [7,15]. On T1-weighted images the EAC and soft tissues within the sub temporal region are thickened and demonstrate reduced T1 signal [5,7].…”

“…On T1-weighted images the EAC and soft tissues within the sub temporal region are thickened and demonstrate reduced T1 signal [5,7]. The T2-weighted sequences return isointense or slightly hyperintense signal intensity.…”

“…However, CT findings of bone erosion and demineralization are late features of NOE. Magnetic resonance imaging better shows changes in soft tissue but it is generally not recommended as a first-line diagnostic imaging modality (given its lower sensitivity for imaging bone erosion compared with CT) [7]. 99mTechnetium Methylene Diphosphonate (99mTc-MDP) planar bone scintigraphy (BS) and single photon emission tomography (SPECT) have proven reliable in early distinction between severe otitis externa and NOE [8].…”