Department of Neurosurgery, Koto Memorial Hospital, 2-1 Hiramatsu-Cho, Higashiohmi-Shi, Shiga, 527-0134, Japan.
Department of Neurosurgery, Indonesia National Brain Center Hospital, East Jakarta, Special Capital Region of Jakarta, Indonesia.
Acta Neurochir (Wien). 2024 Jun 8;166(1):255. doi: 10.1007/s00701-024-06155-2.
In microvascular decompression (MVD) procedures for hemifacial spasm (HFS), surgeons often encounter a rhomboid lip which may obscure the root exit zone (REZ) of the facial nerve. This study aims to explore the anatomical variations of rhomboid lips and their surgical implications to improve safety and effectiveness in MVD surgeries.
A retrospective analysis was conducted on 111 patients treated for HFS between April 2021 and March 2023. The presence of a rhomboid lip was assessed through operative video records, and its characteristics, dissection methods, and impact on nerve decompression outcomes were further examined. Preoperative magnetic resonance imaging (MRI) scans were reviewed for detectability of the rhomboid lip.
Rhomboid lips were identified in 33% of the patients undergoing MVD, with a higher prevalence in females and predominantly on the left side. Two distinct types of rhomboid lips were observed: membranous and cystic variations. The membranous type was noted for its smaller size and position ventral to the choroid plexus. In contrast, the cystic variation was distinguished by its larger size and a thin membrane that envelops the choroid plexus. Preoperative MRI successfully identified rhomboid lips in only 21% of the patients who were later confirmed to have them in the surgical procedures. Surgical approaches primarily involved incisions on the dorsal wall and along the glossopharyngeal nerve root, with only limited need for extensive dissection from lower cranial nerves. Immediate spasm relief was observed in 97% of the patients. One case exhibited a lower cranial nerve deficit accompanied by brainstem infarction, which was caused by the dissection from the lower cranial nerves.
Recognizing the two variations of the rhomboid lip and understanding their anatomical structures are essential for reducing lower cranial nerve injuries and ensuring effective nerve decompression.
在微血管减压（MVD）手术中治疗面肌痉挛（HFS）时，外科医生经常会遇到一个可能会遮挡面神经神经根出口区（REZ）的菱形唇。本研究旨在探讨菱形唇的解剖变异及其对手术的影响，以提高 MVD 手术的安全性和有效性。
对 2021 年 4 月至 2023 年 3 月期间接受 HFS 治疗的 111 例患者进行回顾性分析。通过手术视频记录评估是否存在菱形唇，并进一步检查其特征、解剖方法及其对面神经减压效果的影响。同时回顾术前磁共振成像（MRI）扫描以检测菱形唇的可检测性。
在接受 MVD 的患者中，33%存在菱形唇，女性患者和左侧患者的患病率更高。观察到两种不同类型的菱形唇：膜性和囊性变异。膜性类型的特征是其较小的尺寸和位于脉络丛腹侧的位置。相比之下，囊性变异的特征是其较大的尺寸和包裹脉络丛的薄膜。术前 MRI 仅成功识别出 21%存在菱形唇的患者，这些患者在手术中被证实存在菱形唇。手术入路主要涉及背侧壁和舌咽神经根的切口，仅需要对颅神经进行有限的广泛解剖。97%的患者立即出现痉挛缓解。1 例患者出现颅神经损伤伴脑干梗死，这是由于对颅神经的解剖所致。
认识到菱形唇的两种变异及其解剖结构对于减少颅神经损伤和确保有效的神经减压至关重要。
