Predictive Value of Air Bubble and Meniscus Signs on Routine Trauma Head CT for Nondisplaced Temporal Bone Fractures

BACKGROUND AND PURPOSE: Temporal bone fractures are common in patients with head trauma and can be easily overlooked on routine head CT when nondisplaced. This study evaluated the diagnostic utility of the “meniscus” and “air bubble” signs on standard trauma head CTs in predicting nondisplaced temporal bone fractures. MATERIALS AND METHODS: We retrospectively reviewed 167 patients with head trauma (age 18–93 years) who underwent both a standard noncontrast head CT and a dedicated high-resolution temporal bone CT. A neuroradiologist blindly evaluated head CTs for the presence of a “meniscus” or “air bubble” sign in the external auditory canal and middle ear cavity, as well as presence of mastoid and middle ear cavity opacification. A second neuroradiologist independently reviewed a subset of 50 cases to assess interobserver agreement. A concurrent temporal bone CT served as the reference standard for confirming nondisplaced temporal bone fractures and recording fracture locations. RESULTS: Nondisplaced temporal bone fractures were identified in 103 of 167 patients (61.7%), most commonly involving the mastoid segment (89.3%) and bony external auditory canal (77.7%). The meniscus sign, air bubble sign, mastoid opacification, and middle ear cavity opacification were significantly more frequent in scans positive for nondisplaced temporal bone fractures (60.2%, 68%, 85.4%, 71.8%) compared to negative scans (4.7%, 9.4%, 34.4%, 21.9%) (pCONCLUSIONS: The air bubble and meniscus signs are strong indicators of nondisplaced temporal bone fractures on routine trauma head CT and may support recommending dedicated temporal bone CT to facilitate earlier recognition of subtle fractures.