Would a computed tomography (CT) head non-contrast scan detect mastoiditis?

From the Guidelines

A non-contrast CT scan of the head can detect mastoiditis, but it is not the optimal imaging choice. While a head CT may show some findings of mastoiditis such as fluid in the mastoid air cells, opacification, or bone erosion, a dedicated temporal bone CT with thin slices (1-2mm) is significantly better for evaluating mastoid disease, as suggested by the American College of Radiology Appropriateness Criteria for headache in children 1. The temporal bone CT provides much higher resolution of the mastoid air cells, middle ear structures, and surrounding anatomy, allowing for better visualization of early bone changes, fluid collections, and potential complications.

Key Points to Consider

• CT can be especially helpful in the evaluation for sinusitis and mastoiditis, and may be appropriate in evaluating children with headache related to extracranial infections 1.
• Noncontrast CT scan of the head may be indicated in evaluating children with suspected intracranial infection, often performed before lumbar puncture, but IV contrast is recommended if MRI is not rapidly available 1.
• If mastoiditis is specifically suspected, requesting a dedicated temporal bone CT rather than a standard head CT would be more appropriate, as it provides higher resolution and better visualization of the mastoid air cells and surrounding anatomy.
• MRI can also be valuable, particularly for evaluating intracranial complications of mastoiditis such as abscess formation or venous sinus thrombosis.
• For the most accurate diagnosis of mastoiditis, it is essential to communicate the specific clinical concern to the radiologist so the appropriate imaging protocol can be selected.

From the Research

Detection of Mastoiditis using CT Head Non-Contrast Scan

• The ability of a computed tomography (CT) head non-contrast scan to detect mastoiditis is supported by several studies 2, 3, 4, 5, 6.
• A study published in 2023 found that head CT was used as a diagnostic tool in the emergency department, although clinical signs such as otalgia, protrusion of the auricle, and hyperemia of the mastoid were more predictive of acute mastoiditis 2.
• Another study from 2010 reported a case of acute mastoiditis complicated by an epidural abscess, which was detected using computed tomography and magnetic resonance imaging of the head 3.
• A 2021 study compared the diagnostic performance of MRI with CT in detecting coalescent acute mastoiditis and found that MRI detected definite bone defects with high sensitivity, but was inferior to CT in direct estimation of bone defects 4.
• The use of CT scans in diagnosing acute mastoiditis is also supported by a 2016 study, which found that imaging studies, including CT scans, were performed in 23% of children with acute mastoiditis, primarily to investigate suspected subperiosteal abscess or lack of improvement despite adequate medical therapy 5.
• A 2003 study emphasized the importance of CT in detecting intracranial complications of acute mastoiditis and in determining the type of therapy, with magnetic resonance imaging used as an adjunct in patients with suspected intracranial complications 6.

Limitations of CT Head Non-Contrast Scan

• While CT head non-contrast scans can detect mastoiditis, the studies suggest that clinical signs and symptoms are also important in diagnosis 2.
• The use of CT scans should be reserved for cases where there is a high suspicion of intracranial complications or where clinical diagnosis is uncertain 5.
• MRI may be a useful adjunct to CT in detecting intracranial complications and in evaluating the extent of disease 3, 4, 6.