Department of Neurosurgery, The Jikei University School of Medicine, 3-25-8 Nishishinbashi, Minato-ku, Tokyo, 105-8461, Japan.
Department of Neurosurgery, Omori Red Cross Hospital, 4-30-1 Chuo, Ota-ku, Tokyo, 143-8527, Japan.
Acta Neurochir (Wien). 2021 Jun;163(6):1593-1601. doi: 10.1007/s00701-021-04845-9. Epub 2021 Apr 21.
It is important to distinguish foramen magnum arachnoiditis (FMA) from Chiari malformation (CM) before surgery because the operative strategies for these diseases differ. In the current study, we compared pretreatment magnetic resonance imaging (MRI) of FMA with CM and investigated the MRI findings useful to differentiate between these diseases.
We retrospectively reviewed patients with FMA or CM aged ≥ 18 years who underwent surgeries at our institution between 2007 and 2019. The morphologies of the syrinx, neural elements, and posterior cranial fossa were preoperatively evaluated with MRI. We used the receiver operating characteristic (ROC) curve for the fourth ventricle-to-syrinx distance (FVSD).
Ten patients with FMAs and 179 with CMs were included. FVSD in the FMA group was significantly shorter than that in the CM group (7.5 mm [IQR, 2.8-10 mm] in FMA vs. 29.9 mm [IQR, 16.3-52.9 mm] in CM, p < 0.0001). The other MRI findings that showed the height, size, and length of the syrinx; size of the foramen magnum; degree of cerebellar tonsillar descent; shape of the cerebellar tonsil; and dorsal subarachnoid space at the foramen magnum differed significantly between the two groups. The ROC curve analysis showed that patients whose FVSD was less than 11 mm could be diagnosed with FMA with a specificity of 90% and sensitivity of 96%.
A more cranial syrinx development (FVSD < 11 mm) appears to be the characteristic MRI finding in FMA.
在手术前区分枕骨大孔蛛网膜炎（FMA）和 Chiari 畸形（CM）很重要，因为这两种疾病的手术策略不同。在本研究中，我们比较了 FMA 与 CM 的术前磁共振成像（MRI），并探讨了有助于区分这两种疾病的 MRI 发现。
我们回顾性分析了 2007 年至 2019 年在我院接受手术治疗的 FMA 或 CM 患者，年龄均≥18 岁。使用 MRI 术前评估了脊髓空洞的形态、神经元素和颅后窝。我们使用第四脑室-脊髓空洞距离（FVSD）的接收器工作特征（ROC）曲线。
共纳入 10 例 FMA 患者和 179 例 CM 患者。FMA 组的 FVSD 明显短于 CM 组（FMA 组为 7.5mm[IQR，2.8-10mm]，CM 组为 29.9mm[IQR，16.3-52.9mm]，p<0.0001）。其他 MRI 发现包括脊髓空洞的高度、大小和长度、枕骨大孔大小、小脑扁桃体下降程度、小脑扁桃体形状和枕骨大孔背侧蛛网膜下腔，两组间差异均有统计学意义。ROC 曲线分析显示，FVSD<11mm 的患者可诊断为 FMA，特异性为 90%，敏感性为 96%。
更靠前的脊髓空洞发育（FVSD<11mm）似乎是 FMA 的特征性 MRI 发现。
