F-18 FDG PET/CT in Management of Necrotizing Otitis Externa

Objectives: Necrotizing otitis externa (NOE), also referred to as “malignant otitis externa,” is an uncommon complication of external ear canal infections, resulting in skull base osteomyelitis. Multiple pathogens have been implicated, the most common of which is Pseudomonas aeruginosa. Risk factors include diabetes, advanced age, and immunocompromised status. Clinical features include unremitting otalgia, otorrhea, headache, and cranial nerve involvement. Treatment consists of prolonged parenteral antibiotics and selective surgical debridement. Inadequate treatment of NOE is associated with significant morbidities, including relapsed infection, cranial nerve palsy, and stroke. A high index of suspicion of NOE is necessary in order to optimize clinical outcomes for this potentially deadly infection. Imaging is a key component of both the initial assessment of suspected NOE and confirmation of full response to treatment. Multiple imaging modalities have historically been used with varied levels of diagnostic sensitivity and specificity, including CT, MRI, Tc-99m MDP, radiolabeled white cells, and Ga-67 citrate. F-18 FDG, which has traditionally been used for oncologic imaging, is also emerging as a highly sensitive infection imaging agent. This educational exhibit presents imaging and clinical findings of two recent NOE patients who underwent pre- and post-treatment evaluation using F-18 FDG PET/CT. The discussion which follows will educate clinicians regarding appropriate use of this novel imaging technique, with emphases on logistics, costs, and clinical value compared to traditional NOE imaging agents. Key diagnostic criteria will also be suggested to assist in accurate image interpretation.