Purpose

Current imaging standard for acute mastoiditis (AM) is contrast-enhanced computed tomography (CT), revealing inflammation-induced bone destruction, whereas magnetic resonance imaging (MRI) outperforms CT in detecting intracranial infection. Our aim was to compare the diagnostic performance of MRI with CT in detecting coalescent AM and see to which extent MRI alone would suffice to diagnose or rule out this condition.

Methods

The MR images of 32 patients with AM were retrospectively analyzed. Bone destruction was evaluated from T2 turbo spin echo (TSE) and T1 Gd magnetization-prepared rapid acquisition with gradient echo (MPRAGE) images. Intramastoid enhancement and diffusion restriction were evaluated subjectively and intramastoid apparent diffusion coefficient (ADC) values were measured. The MRI findings were compared with contrast-enhanced CT findings of the same patients within 48 h of the MR scan.

Results

Depending on the anatomical subsite, MRI detected definite bone defects with a sensitivity of 100% and a specificity of 54–82%. Exception was the inner cortical table where sensitivity was only 14% and specificity was 76%. Sensitivity for general coalescent mastoiditis remained 100% due to multiple coexisting lesions. The absence of intense enhancement and non-restricted diffusion had a high negative predictive value for coalescent mastoiditis: an intramastoid ADC above 1.2 × 10⁻³ mm²/s excluded coalescent mastoiditis with a negative predictive value of 92%.

Conclusion

The MRI did not miss coalescent mastoiditis but was inferior to CT in direct estimation of bone defects. When enhancement and diffusion characteristics are also considered, MRI enables dividing patients into low, intermediate and high-risk categories with respect to coalescent mastoiditis, where only the intermediate risk group is likely to benefit from additional CT.

中文翻译：

---

与 CT 相比，MRI 对合并性急性乳突炎的检测。

目的

目前急性乳突炎 (AM) 的成像标准是对比增强计算机断层扫描 (CT)，可显示炎症引起的骨破坏，而磁共振成像 (MRI) 在检测颅内感染方面优于 CT。我们的目的是比较 MRI 与 CT 在检测合并 AM 方面的诊断性能，并了解仅 MRI 在多大程度上足以诊断或排除这种情况。

方法

回顾性分析32例AM患者的MR图像。从 T2 涡轮自旋回波 (TSE) 和 T1 Gd 磁化准备的梯度回波 (MPRAGE) 图像快速采集评估骨破坏。主观评价乳突内增强和扩散限制，并测量乳突内表观扩散系数（ADC）值。将 MRI 结果与 MR 扫描后 48 小时内相同患者的对比增强 CT 结果进行比较。

结果

根据解剖亚位点，MRI 检测到明确的骨缺损，敏感性为 100%，特异性为 54-82%。例外是内皮层表，其敏感性仅为 14%，特异性为 76%。由于多个并存病灶，对一般合并性乳突炎的敏感性仍为 100%。没有强烈的增强和非限制性扩散对合并乳突炎具有很高的阴性预测值：乳突内 ADC 高于 1.2 × 10 ^-3  mm ² /s 排除合并乳突炎，阴性预测值为 92%。

结论

MRI 并未漏诊合并乳突炎，但在直接评估骨缺损方面不如 CT。当还考虑增强和弥散特征时，MRI 可以将患者分为低、中和高风险类别，其中只有中风险组可能从额外的 CT 中受益。