Ming Xu1,2,3,4,5,6, Jian Xu1,2,3,4,5,6, Mingyu Chen1,2,3,4,5,6, Ying Wang1,2,3,4,5,6, Ping Zhong7,8,9,10,11,12. 1. Department of Neurosurgery, Huashan Hospital, Shanghai Medical College, Fudan University, Shanghai, China. 2. National Center for Neurological Disorders, Shanghai, China. 3. Shanghai Key Laboratory of Brain Function Restoration and Neural Regeneration, Shanghai, China. 4. Neurosurgical Institute of Fudan University, Shanghai, China. 5. Shanghai Clinical Medical Center of Neurosurgery, Shanghai, China. 6. Research Units of New Technologies of Micro-Endoscopy Combination in Skull Base Surgery, Chinese Academy of Medical Sciences, Shanghai, China. 7. Department of Neurosurgery, Huashan Hospital, Shanghai Medical College, Fudan University, Shanghai, China. zhp228899@163.com. 8. National Center for Neurological Disorders, Shanghai, China. zhp228899@163.com. 9. Shanghai Key Laboratory of Brain Function Restoration and Neural Regeneration, Shanghai, China. zhp228899@163.com. 10. Neurosurgical Institute of Fudan University, Shanghai, China. zhp228899@163.com. 11. Shanghai Clinical Medical Center of Neurosurgery, Shanghai, China. zhp228899@163.com. 12. Research Units of New Technologies of Micro-Endoscopy Combination in Skull Base Surgery, Chinese Academy of Medical Sciences, Shanghai, China. zhp228899@163.com.
Abstract
BACKGROUND: 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. METHODS: 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. RESULTS: 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. CONCLUSION: 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.
BACKGROUND: 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. METHODS: 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. RESULTS: 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. CONCLUSION: 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.