Prognostic Value of Extension Patterns on Follow-up Magnetic Resonance Imaging in Patients With Necrotizing Otitis Externa

Objectives: To analyze the clinical characteristics of necrotizing otitis externa (NOE) and to evaluate the prognosis according to the progression of disease in terms of extension patterns on follow-up magnetic resonance images. Design: A retrospective clinical study. Setting: Tertiary academic center. Patients: We reviewed medical records of 36 patients with NOE followed up by temporal bone magnetic resonance images on a regular basis from January 1, 1992, through December 31, 2008. Main Outcome Measures: The initial compartments affected by NOE were defined as 4 categories: anterior, medial, midline, and intracranial and extracranial. The extensions of NOE were evaluated by comparison between initial and follow-up magnetic resonance images 6 months later and defined by the direction of spread from one to another compartment and/or disease progression within the same compartment. The patients were divided into 3 groups (limited, single, and multiple extension groups) on the basis of the multiplicity of extension routes. The clinical characteristics and prognostic factors were investigated, and overall survival rates were compared according to extension patterns. Results: Retrocondylar fat infiltration (86%) was the most common finding, followed by parapharyngeal fat infiltration (81%) and ipsilateral nasopharyngeal musculature thickening (75%). Anterior and medial extension patterns were observed in 3 (8%) and 5 (14%) patients, respectively. Eighteen patients (50%) with combined extension patterns showed a significantly lower overall survival rate than those with single and limited extension patterns (P=.01). Conclusion: The retrocondylar fat infiltration was the earliest change in NOE, and combined extension patterns may be a poor prognostic factor in patients with NOE.