CT findings in temporal bone sites in skull base osteomyelitis from malignant otitis externa

Objectives To identify the earliest sites and spread patterns of bony erosions on high-resolution temporal bone computerized tomographic (HRTBCT) scans and conjugate the radiological findings with clinical/laboratory data for guiding the interpretation of CT images of skull base osteomyelitis (SBOM) from malignant otitis externa (MOE). Study design Retrospective and prospective medical records analysis. Methods The medical records of all patients who presented to a referral medical center during 2015-2022 and initially diagnosed with SBOM. Radiological assessment of each sub-site was performed by 2 qualified neuro-radiologist, who were blind to the clinical data. Results 33 patients were enrolled. All patients suffered edema and exudates of the external auditory canal (EAC). The most common osseous markers for SBOM were dehiscence or irregularity of the anterior EAC wall and temporomandibular joint (TMJ) medial wall (21/33, 64% patients, each), followed by a fistula from the TMJ to the EAC (20/33, 61% patients). Eustachian tube bony walls and condylar irregularity and/or dehiscence were as prevalent as 16/33, 48% of patients, each. EAC inferior and posterior walls of the EACs were irregular or dehiscent in patients with more advanced disease. Conclusions The high symptomatologic overlap between SBOM and other aural pathologies might cause diagnostic (and subsequent treatment) delay and result in dire complications. EAC edema and irregularity or dehiscence of the anterior EAC wall are the most common early CT findings associated with SBOM caused by MOE.