Computed Tomography and the Diagnosis of Coalescent Mastoiditis

Abstract

OBJECTIVE: To evaluate the sensitivity and accuracy of temporal bone CT findings for the diagnosis of acute coalescent mastoiditis. DESIGN: CT scans were blindly scored for mastoid bone integrity (air cell septae, sigmoid cortical plate, and lateral cortical wall) by an otologist and 2 neuroradiologists. Scores were analyzed to determine their sensitivity and specificity for acute coalescent mastoiditis. SUBJECTS: Twenty-one patients with acute coalescent mastoiditis or acute noncoalescent mastoiditis and 12 patients with chronic mastoiditis. SETTING: Academic tertiary care facility. RESULTS: Pair-wise interobserver agreement was good to excellent (κ = 0.4 to 0.83) for the sigmoid plate, the lateral cortex, and the septae. Scores for the sigmoid plate were significantly greater (indicative of greater bone destruction) in the coalescent group than in either the noncoalescent group or the chronic group ( P < 0.05). Within the coalescent group, scores were highest for the sigmoid plate, followed by the septae and the lateral wall. Sensitivity and specificity for coalescent mastoiditis were both highest for the sigmoid plate (67% and 90%, respectively). CONCLUSIONS: Erosion of the cortical plate overlying the sigmoid sinus is the most sensitive and specific CT finding for distinguishing coalescent from noncoalescent acute mastoiditis.