From the Guidelines
For otalgia (ear pain), a CT scan of the temporal bone should typically be performed without contrast. This is because the bony structures of the temporal bone, which are often the focus of evaluation in cases of ear pain, are well visualized without the need for contrast enhancement, as noted in the 2023 update of the ACR Appropriateness Criteria for tinnitus 1. Non-contrast CT is excellent for detecting structural abnormalities such as fractures, erosions, mastoid disease, cholesteatoma, and otosclerosis.
Some key points to consider when evaluating otalgia with CT temporal bone include:
- The ability to detect conditions like otospongiosis, Paget disease, sigmoid sinus diverticulum, and sigmoid sinus dehiscence without the need for contrast 1.
- The usefulness of CT temporal bone without IV contrast in distinguishing between retrotympanic masses and vascular variants, thus avoiding unnecessary biopsies 1.
- The appropriateness of CT temporal bone without contrast for evaluating lesions such as glomus tympanicum and vascular variants like aberrant internal carotid artery (ICA) when a retrotympanic lesion is suspected on otoscopy 1.
Contrast would only be necessary if there is suspicion of infection with abscess formation, tumor, or vascular pathology. The radiation dose for a non-contrast temporal bone CT is lower, and it avoids potential risks associated with contrast agents such as allergic reactions or kidney problems. If the initial non-contrast CT is inconclusive and there is clinical suspicion for inflammatory or neoplastic processes, a follow-up MRI with contrast might be more appropriate than a contrast-enhanced CT for further evaluation of soft tissue pathology.
From the Research
CT Temporal Bone for Otalgia
When it comes to evaluating otalgia using a CT temporal bone scan, the decision to use contrast or not depends on the clinical context and suspected underlying cause.
- The study 2 describes CT findings in temporal bone osteoradionecrosis, where contrast was used to identify enhancing soft tissue, which is more commonly seen in moderate or severe cases.
- However, for primary otologic causes of otalgia, such as acute otitis media or otitis externa, a non-contrast CT scan may be sufficient 3.
- In cases of suspected referred otalgia, where the pain is not originating from the ear itself, a contrast-enhanced CT scan may be more useful in identifying underlying causes such as temporomandibular joint disorders, dental pathology, or head and neck malignancy 4.
- A systematic approach to evaluating temporal bone CT scans, as outlined in 5, can help ensure that all relevant structures are assessed, regardless of whether contrast is used.
Key Considerations
- The use of contrast in CT temporal bone scans for otalgia should be guided by the clinical presentation and suspected underlying cause.
- A thorough understanding of the possible causes of otalgia, including primary otologic and referred causes, is essential for selecting the appropriate imaging protocol.
- A systematic approach to evaluating temporal bone CT scans can help ensure that all relevant structures are assessed, regardless of whether contrast is used.