Department of Neurosurgery, Huashan Hospital, Shanghai Medical College, Fudan University, Shanghai, China.
National Center for Neurological Disorders, Shanghai, China.
Acta Neurochir (Wien). 2022 Sep;164(9):2483-2490. doi: 10.1007/s00701-022-05288-6. Epub 2022 Jul 1.
An anomalous subarcuate loop (SL) of the anteroinferior cerebellar artery (AICA) is a rare anatomic variation, which increases the complexity and risk of vestibular schwannoma (VS) removal. However, preoperative diagnosis of this anomaly remains difficult. The aim of this study was to report three types of anomalous SLs encountered during VS removal and to describe the "Deep Subarcuate Fossa (SF)" sign and its significance in the diagnosis and treatment of an osseous-penetrating SL.
We prospectively observed 963 patients with newly/recently diagnosed VS who underwent surgical treatment performed by the senior author (P.Z.) from 2012 to 2021 and identified 16 patients with an anomalous SL. The SF was retrospectively measured on preoperative thin-slice temporal bone computed tomography in 963 patients.
Three types of anomalous SLs were encountered during VS removal: the apex of the SL was embedded in the dorsal tumor capsule (type I, 1 case), the dura (type II, 8 cases), or the dura and bone (type III, 7 cases) surrounding the SF. The depth of the SF in 7 patients with a type III anomalous SL ranged from 2.3 to 7.0 mm (3.56 ± 1.56 mm), which was significantly larger than that in 845 patients without an osseous-penetrating SL (1.23 ± 0.43 mm) (p = 0.008). When the depth of the SF exceeded 2 mm, the sensitivity and precision of the diagnosis of a type III anomalous SL were 100% (7/7) and 31.8% (7/22), respectively.
Three types of anomalous SLs may be encountered during VS removal, and AICA displacement is recommended before tumor removal. The "Deep SF" sign may indicate the existence of a type III anomalous SL and it can predict the depth of the AICA in the bone and guide the drilling of the bone around the vessel loop.
小脑前下动脉（AICA）的异常弓下环（SL）是一种罕见的解剖变异，增加了听神经瘤（VS）切除的复杂性和风险。然而，这种异常的术前诊断仍然很困难。本研究旨在报告在 VS 切除过程中遇到的三种类型的异常 SL，并描述“深弓下窝（SF）”征及其在诊断和治疗骨穿透性 SL 中的意义。
我们前瞻性观察了 2012 年至 2021 年由高级作者（P.Z.）进行手术治疗的 963 例新/近期诊断为 VS 的患者，并确定了 16 例异常 SL 患者。在 963 例患者的术前薄层颞骨 CT 上回顾性测量 SF。
在 VS 切除过程中遇到了三种类型的异常 SL：SL 的尖端嵌入肿瘤囊的背侧（I 型，1 例）、硬脑膜（II 型，8 例）或围绕 SF 的硬脑膜和骨（III 型，7 例）。7 例 III 型异常 SL 的 SF 深度为 2.3 至 7.0mm（3.56±1.56mm），明显大于无骨穿透性 SL 的 845 例患者（1.23±0.43mm）（p=0.008）。当 SF 深度超过 2mm 时，III 型异常 SL 的诊断灵敏度和精度分别为 100%（7/7）和 31.8%（7/22）。
在 VS 切除过程中可能会遇到三种类型的异常 SL，建议在肿瘤切除前先移动 AICA。“深 SF”征可能提示存在 III 型异常 SL，并可预测 AICA 在骨中的深度，指导血管环周围骨的钻孔。
