Malignant otitis externa (MOE), also known as necrotizing otitis externa, is a rare and severe infection of the external ear canal. It is typically caused by the bacterium Pseudomonas aeruginosa. MOE primarily affects individuals with compromised immune systems, such as the elderly or those with diabetes. The infection starts in the ear canal and can spread to surrounding tissues, including the skull base.

The clinical presentation of MOE is characterized by severe ear pain, foul-smelling discharge, hearing loss, and swelling in the affected area. Left untreated, MOE can lead to serious complications, such as bone erosion, cranial nerve involvement, and even spread to nearby structures like the brain.

MRI plays a crucial role in diagnosing and staging MOE. On MRI, findings consistent with MOE include soft tissue inflammation and edema in the external ear canal, extending to the adjacent temporal bone and skull base. The involved structures may demonstrate enhancement following the administration of contrast material. MRI can also help identify complications such as abscess formation, osteomyelitis, and involvement of the cranial nerves or nearby blood vessels.

Additionally, MRI can aid in monitoring the response to treatment and assessing disease progression. It provides detailed anatomical information and helps guide clinicians in determining the extent of the infection, planning surgical interventions if necessary, and evaluating the overall response to therapy.