Magnetic resonance imaging and computerized tomography in malignant external otitis

Abstract

In malignant external otitis (MEO), determining the anatomic extent of disease and evaluating the physiologic response to therapy remain a problem. Magnetic resonance imaging (MRI) has recently become available in limited clinical settings. Four patients with MEO were evaluated using MRI, computerized tomography (CT), technetium-99 (Tc-99) bone scanning, and gallium-67 citrate (Ga-67 citrate) scanning. MRI is superior to CT, Tc-99 bone scanning, and Ga-67 citrate scanning in evaluating the anatomic extent of soft tissue changes in MEO. MRI alone cannot be relied upon to determine the physiologic response to therapy. MRI can, however, serve as a valuable guide to the interpretation of Tc-99 bone and Ga-67 citrate scans, and in this respect, MRI is extremely useful in the treatment of MEO.

Malignant External Otitis: Review and Personal Experience

“…It can reveal inflammatory changes in the soft tissues of the tympanic cavity and mastoid, infratemporal fossa, parapharyngeal space, and nasopharynx, as well as in the area of the stylomastoid foramen, where facial nerve involvement most frequently occurs (42,(44)(45)(46).…”

“…Moreover, when an area of osteomyelitis that has already been revealed by CT regresses, the diagnostic image only rarely reverts to normal, and even then after considerable delay. For this reason, CT is of little use when assessing response to therapy (27,45).…”

Use of magnetic resonance imaging as the primary imaging modality in the diagnosis and follow-up of malignant external otitis

“…7 The ideal study would also allow the clinician to determine at which point the infection had been completely eradicated so that potentially toxic systemic antibiotics could be discontinued as soon as possible. 7 therapy.…”

“…10 CT scanning is currently the gold standard imaging investigation in MEO and can clearly demonstrate the progression of bone erosion once significant demineralization has occurred. 7 However, the efficacy of CT scanning is limited by the slow rate at which bone remineralizes with cure, and hence it is difficult to assess any response to therapy based on CT scanning alone. 2,7 MRI offers submillimeter spatial resolution and axial, coronal and sagittal images are readily obtained.…”

Temporal bone osteomyelitis and temporoparietal abscess secondary to malignant otitis externa

“…Once demineralisation occurs, a CT scan rarely returns to normal and thus is not a reliable modality in assessing response to therapy. 9 Imaging of the skull base in the setting of cranial neuropathy and probable infection is best accomplished with MRI. This modality has the advantage of better soft tissue discrimination than CT, and it is particularly useful for assessing soft tissue planes around the skull base and abnormalities of the medullary cavity of bone.…”