Optimal Diagnostic Criteria and a Staging System for Otogenic Skull Base Osteomyelitis

Abstract

Objective Diagnostic criteria for otogenic skull base osteomyelitis (SBO) have been conflicting among researchers. We aimed to propose clinically useful diagnostic criteria and a staging system for otogenic SBO that is associated with infection control and mortality. Design The present study is designed as a retrospective one. Setting This study was conducted at the University Hospital. Participants Thirteen patients with otogenic SBO who met the novel rigorous diagnostic criteria consisted of symptomatic and radiological signs on high-resolution computed tomography (HRCT) and magnetic resonance imaging (MRI). Simple refractory external otitis was not included. A staging system according to disease extent revealed by HRCT and MRI is proposed: lesions limited to the temporal bone (stage 1), extending to less than half (stage 2), exceeding the midline (stage 3), and extending to the whole of the clivus (stage 4). All patients received long-term antibiotic therapy. Patients were divided into infection-uncontrolled or -controlled groups based on symptoms, otoscopic findings, and C-reactive protein level at the last follow-up. The mean follow-up period was 27.7 months. Main Outcome Measures Possible prognostic factors, such as immunocompromised status and symptoms, including cranial nerve palsy, pretreatment laboratory data, and treatments, were compared between the infection-uncontrolled and -controlled groups. Disease stages were correlated with infection control and mortality. Results The infection-uncontrolled rate and mortality rate were 38.5 and 23.1%, respectively. There were no significant differences in possible prognostic factors between the infection-uncontrolled and -controlled groups. HRCT-based stages significantly correlated with infection control and mortality. Conclusion We proposed here the clinically useful diagnostic criteria and staging systems that can predict infection control and prognosis of otogenic SBO.

Keywords: HRCT; MRI; diagnostic criteria; infection control; malignant external otitis; mortality; skull base osteomyelitis; staging.

Fig. 1

HRCT-based stages of otogenic skull base osteomyelitis. HRCT images were classified into four stages according to the cortical bone destruction. Arrow heads indicate areas of cortical bone destruction in the petrous portion of temporal bone. Arrows indicate areas of cortical bone destruction in the clivus. HRCT, high-resolution computed tomography.

Fig. 2

MRI-based stages of otogenic skull base osteomyelitis. MRI images were classified into four stages according to the low signal intensity area on T1WI. Arrow heads indicate areas of low signal intensity of bone marrow in the petrous portion of temporal bone and soft tissue in the infratemporal fossa. Arrows indicate areas of low signal intensity in the clivus. The images are from the same patients as in Fig. 1 . MRI, magnetic resonance imaging; T1WI, T1-weighted image.