Computer tomography findings in necrotizing otitis externa based on the offending pathogens

High-resolution temporal bone computer tomography (HRTBCT) is the most common initial radiological modality used for the assessment of necrotizing otitis externa (NOE).

(1) To compare the extension of disease, as seen on HRTBCT, in patients with NOE caused by different pathogens and (2) assess whether radiological findings may suggest the offending pathogen in cases of sterile-NOE.

All NOE patients were hospitalized between 1990 and 2018. All patients underwent HRTBCT at admission. Three groups (fungus-NOE, PA-NOE and sterile-NOE) comprising of ten patients each were randomly selected. HRTBCT was reevaluated by a senior radiologist. Thirteen radiological subsites were selected for reevaluation.

All patients in the fungal-NOE group complained of otalgia, compared to nine in the sterile-NOE and six in the PA-NOE groups (p value = 0.044). External ear canal edema and granulation tissue were the most common findings in all groups. Surgery was performed in five patients in the fungal-NOE and PA-NOE and three in the sterile-NOE group (p value =  > 0.05). Radiological findings indicating severe bone erosion within the EEC was seen in all patients but 3 (p value =  > 0.05). Severe TMJ erosion was seen in one patient within the fungal-NOE and PA-NOE group (p value =  > 0.05). When mild and severe involvement were combined, TMJ bone erosion was seen in four patients in the fungal-NOE and only in one patient in the PA-NOE (p = 0.04).

TMJ involvement may be more common in fungal disease, suggesting a different spreading pathway, as opposed to PA-NOE. Accordingly, TMJ involvement on HRTBCT may justify antifungal treatment in sterile culture-NOE.