Temporal Bone Encephaloceles: Utility of Preoperative Imaging

Objective: To determine the diagnostic efficacy and clinical value of preoperative computed tomography (CT) and magnetic resonance imaging (MRI) among patients with suspected temporal bone encephaloceles (TBE). Study Design: Retrospective chart review from 2006 to 2018. Setting: Tertiary referral center. Subjects and Methods: The subjects underwent surgery for a clinically suspected TBE or cerebrospinal fluid (CSF) leak. Preoperative imaging test characteristics of CT and MRI, including sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV), were calculated for TBE scans and compared with intraoperative findings. Results: Fifty-seven subjects with otorrhea, middle ear effusion, hearing loss, and/or meningitis with suspected TBE or CSF leak were identified. All had preoperative CT scans, and 61% (35/57) had preoperative MRI scans. Intraoperatively, 37 of 57 patients (65%) were found to have a TBE. CT scans (17% sensitivity, 100% specificity, 100% PPV, 46% NPV) were less sensitive than MRI (58% sensitivity, 100% specificity, 100% PPV, 24% NPV) for detecting TBEs. Furthermore, the time from initial scan to operative repair was significantly longer in those who had a CT followed by MRI scan compared with CT alone or a fused CT-MRI scan (mean = 68 vs 15 days, respectively; P =.004). Conclusion: CT and MRI provide complementary information that may aid surgical planning. However, imaging cannot always rule out TBE. In cases with high clinical suspicion, surgical confirmation is often required for definitive diagnosis and treatment. The cost of an additional preoperative study should be considered before its use.