Ontario Veterinary College Health Science Centre, University of Guelph, Guelph, ON, Canada.
Department of Clinical Studies, University of Guelph, Guelph, ON, Canada.
J Feline Med Surg. 2023 Apr;25(4):1098612X231168001. doi: 10.1177/1098612X231168001.
Otitis media/interna (OMI) is the most common cause of peripheral vestibular disease in cats. The inner ear contains endolymph and perilymph, with perilymph being very similar in composition to cerebrospinal fluid (CSF). As a very-low-protein fluid, it would be expected that normal perilymph should suppress on fluid-attenuated inversion recovery (FLAIR) MRI sequences. Based on this, we hypothesized that MRI FLAIR sequences should provide a non-invasive way of diagnosing inflammatory/infectious diseases such as OMI in cats, something that has previously been demonstrated in humans and, more recently, in dogs.
This was a retrospective cohort study in which 41 cats met the inclusion criteria. They were placed into one of four groups, based on presenting complaint: clinical OMI (group A); inflammatory central nervous system (CNS) disease (group B); non-inflammatory structural disease (group C); and normal brain MRI (control group; group D). Transverse T2-weighted and FLAIR MRI sequences at the level of the inner ears bilaterally were compared in each group. The inner ear was selected as a region of interest using Horos, with a FLAIR suppression ratio calculated to account for variability in signal intensity between MRIs. This FLAIR suppression ratio was then compared between groups. Statistical analyses were performed by an experienced statistician, with a general linear model used to compare mean FLAIR suppression ratio, CSF nucleated cell count and CSF protein concentration between groups.
The OMI group (group A) had significantly lower FLAIR suppression scores compared with all other groups. The CSF cell count was also significantly increased in the OMI (group A) and inflammatory CNS disease (group B) groups compared with the control group (group D).
This study demonstrates the utility of MRI FLAIR sequences in diagnosing presumptive OMI in cats, similarly to in humans and dogs. This study is relevant to practicing veterinary neurologists and radiologists in interpreting MRI findings in cats with suspected OMI.
中耳炎（OMI）是猫外周前庭疾病最常见的原因。内耳包含内淋巴和外淋巴，外淋巴在组成上与脑脊液（CSF）非常相似。由于它是一种低蛋白液体，预计正常外淋巴在外液衰减反转恢复（FLAIR）MRI 序列中应该会受到抑制。基于这一点，我们假设 MRI FLAIR 序列可以为诊断猫的 OMI 等炎症/感染性疾病提供一种非侵入性的方法，这在人类和最近的犬类中已经得到证实。
这是一项回顾性队列研究，其中 41 只猫符合纳入标准。根据主诉，将它们分为以下四组：临床 OMI（A 组）；炎症性中枢神经系统（CNS）疾病（B 组）；非炎症性结构性疾病（C 组）；正常脑 MRI（对照组；D 组）。比较了每组双侧内耳的横向 T2 加权和 FLAIR MRI 序列。使用 Horos 选择内耳作为感兴趣区，并计算 FLAIR 抑制率以解释 MRI 之间信号强度的可变性。然后比较各组之间的 FLAIR 抑制率。由经验丰富的统计学家进行统计分析，使用一般线性模型比较组间平均 FLAIR 抑制率、CSF 有核细胞计数和 CSF 蛋白浓度。
OMI 组（A 组）的 FLAIR 抑制评分明显低于其他所有组。与对照组（D 组）相比，OMI（A 组）和炎症性 CNS 疾病（B 组）组的 CSF 细胞计数也明显增加。
本研究证明了 MRI FLAIR 序列在诊断猫疑似 OMI 中的效用，与人类和犬类相似。本研究与怀疑患有 OMI 的猫的 MRI 解读相关，对兽医神经科医生和放射科医生具有重要意义。
