Gray-Scale Inversion on High Resolution Computed Tomography of the Temporal Bone: An Observational Study

Objectives: This is a qualitative study to explore the utility of gray-scale inversion or the “invert” function of high-resolution computed tomography (HRCT) scans in the diagnosis of temporal bone anatomy and pathology. Methods: This is a case series describing an innovative application of an existing image processing tool to visualize temporal bone anatomy and pathology. Illustrative patients at a tertiary referral center with otologic symptoms and findings leading to HRCT scans of the temporal bone were included. Diagnostic HRCT scans were evaluated utilizing the gray-scale inversion function (invert function). Results: Nine illustrative cases which demonstrate conditions such as persistent stapedial artery, membranous stapes footplate, total ossicular prosthesis migration into the vestibule, third window syndrome such as superior semicircular canal dehiscence (SSCD) and cochlea-facial nerve dehiscence, otosclerosis, and ossicular chain discontinuity are included. The enhanced visualization was confirmed surgically in 3 cases, and 1 had physiological confirmation using cervical vestibular evoked myogenic potentials (cVEMP). Conclusions: Gray-scale inversion can be used to improve visualization of temporal bone anatomy and pathologic changes when diagnoses are in doubt. The invert function is a useful adjunct in the armamentarium of both radiologists and otologists when evaluating HRCT of the temporal bone.