Related Experiment Video
Updated: May 31, 2026
Advanced Diffusion Imaging in The Hippocampus of Rats with Mild Traumatic Brain Injury
Published on: August 14, 2019
Predictive Value of Air Bubble and Meniscus Signs on Routine Trauma Head CT for Nondisplaced Temporal Bone Fractures
Omar Azrak1, Aleeshah Nasir2, Bilal Battal2
1From the Department of Radiology (O.A., B.B., S.-C.H., C.Z.), Psychiatry (A.N.), University of North Carolina at Chapel Hill School of Medicine, Chapel Hill, NC, USA and HCA Florida Oak Hill Hospital (O.A.), Brooksville, FL, USA. Omar_azrak@med.unc.edu.
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%) (p<0.0001 for all). The meniscus sign showed the highest odds ratio (30.7, 95% CI: 9.03-104.6), with 60.2% (95% CI: 50.5%-69.1%) sensitivity and 95.3% (95% CI: 87.1%-98.4%) specificity. Mastoid opacification had the highest sensitivity (85.4%, 95% CI: 77.4%-91%) but low specificity (65.6%, 95% CI: 53.4%-76.1%). Combining the meniscus and air bubble signs increased sensitivity to 80.6% (95% CI: 71.9%-87.1%) and decreased specificity to 87.5% (95% CI: 77.2%-93.5%), improving the overall diagnostic performance for detecting nondisplaced temporal bone fractures. Interobserver agreement was substantial to almost perfect (kappa 0.72-0.92).
Conclusions:
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.
