목적: skull base osteomyelitis (SBO) was fist descrived at 1959 by Meltzer and Keleman. SBO is diagnosed, when osteitis of the temporal bone and skull base is evident. Patients prone to occur skull base osteomyeilitis are usually diabetic or immunocompromised. If external auditory canal infection is undertreated in these patients, the infection may advance to surrounding structure such as skull base via fissure of Santorini, and tympanomastoid suture. Although most of SBO originated in canal infection, a few cases report SBO after mastoidectomy. Here, we reviewed patients with SBO after mastoidectomy, initially diagnosed as chronic otitis media. 방법:We designed retrospective study to review patients with SBO from Jan 2008 to Dec 2014. To analyse the relation of mastoidectomy and SBO, we chose the patients whose preoperative temporal bone CT was available. 결과:5 patients were enrolled in this study. 3 patients were male and the other 2 were female. All patients were diagnosed as chronic otitis media with cholesteatoma. All patients were medicated with hypertension and 3 patients of them were also medicated for diabetes. 4 patients were operated in outside hospitals and referred for SBO after mastoidectomy. 1 patients were operated in our hospital. After mastoidectomy, average 71 days were taken for diagnosis of SBO by temporal bone CT and temporal bone magnetic resonance image (MRI). 5 patients were complicated with cranial nerve palsy and 1 patient had a stroke due to lateral thrombophlebitis. 결론:We reviewed the preoperative temporal bone CT to evaluate the risk for SBO. Minimal bony destruction around skull base missed at initial diagnosis were observed in all cases. Especially, 4 cases had bony destruction at lateral wall of carotid canal, and 1 case had natural defect of jugular plate. We thought 4 cases were misdiagnosed as chronic otitis media, even if the presence of SBO. In latter case, the defect might be route for transmission of disease to skull base.