Analysis of prognostic factors in malignant external otitis

Abstract

Malignant external otitis (MEO) is a potentially fatal infection of the external auditory canal, temporal bone, and skull base. Despite the treatment with modern antibiotics, MEO can lead to skull base osteomyelitis, but until now there have been few studies on prognostic factors in MEO. And there are debates that the factor previously considered to be a prognostic indicator was not actually related to the outcome of MEO. We performed a retrospective study to identify prognostic factors and a meta-analysis of other articles on MEO. Based on disease progression, the 28 patients were divided into the ‘controlled’ and ‘uncontrolled’ groups, with 12 and 16 patients, respectively. We identified three categories of prognostic factor: factors relating to patient, disease, and treatment. We compared prognostic factors between the controlled and uncontrolled groups. In our series, the duration of diabetes mellitus (DM), inflammatory markers (C-reactive protein and erythrocyte sedimentation rate), and computed tomography (CT) or magnetic resonance imaging (MRI) findings did influence the prognosis of MEO. In contrast, prognosis was unrelated to age, gender, mean glucose level, HbA1c, pathogen, comorbidity, or cranial nerve involvement. There was no factor relating to treatment correlated to the prognosis, such as surgery, steroid therapy, or the interval to the first proper treatment. Cranial nerve involvement is associated with disease progression, but cranial nerve involvement and the prognosis of MEO remain controversial. We also conducted a meta-analysis of cranial nerve involvement as a prognostic factor. Our results showed that cranial nerve involvement has a statistically significance on the prognosis of MEO. Therefore, we found that glucose control in diabetes mellitus, cranial nerve involvement and disease extent in imaging modalities that were controversial previously were related to the prognosis of MEO. We suggest that significant prognostic factors should be monitored to anticipate the prognosis of patients with MEO