Ujihara Masaki, Kobayashi Masahito, Sato Masaya, Hirata Sachiko, Takabatake Kazuhiko, Fujimaki Takamitsu
Department of Neurosurgery, Saitama Medical University, 38 Morohongo, Moroyama-machi, Saitama, Japan.
Neurosurg Rev. 2025 Jul 22;48(1):578. doi: 10.1007/s10143-025-03734-4.
Microvascular decompression (MVD) for hemifacial spasm (HFS) involves retraction of the cerebellar flocculus to monitor any neurovascular compression at the facial nerve root exit zone (REZ). Even so, identification of neurovascular compression may be challenging in some cases, due to a "large" or "hypertrophic" flocculus. We have frequently encountered cases where the REZ remains poorly visible despite the flocculus appearing normal in size on MRI. Accordingly, we hypothesized that the anatomical relationship between the flocculus and the REZ, rather than flocculus size, is the key factor affecting REZ visibility. In this retrospective observational study, we examined the correlation between preoperative MRI findings and REZ visibility during MVD for HFS. We measured the size of the flocculus and evaluated its degree of medial extension, i.e. whether its medial border extended beyond the facial nerve REZ, in three-dimensional images. REZ visibility was assessed through retrospective review of surgical videos. We also examined whether REZ visibility affected the surgical outcome using grading scores. Sixty-five patients were included in the study. The REZ was successfully visualized under a surgical microscope in 53 cases and not visualized in 12 cases, the flocculus volume being 0.37 ml and 0.41 ml, respectively, with no significant intergroup difference (P =.23). Medial extension of the flocculus was observed in 1 (1.9%) and 5 (41.7%) of these cases, respectively, the difference being significant (P =.0002). There were no significant intergroup differences in MVD effectiveness (P =.88) or complications (P =.41). We have revealed a novel anatomical variation, "medial extension of the flocculus," that significantly impacts facial nerve REZ visibility during MVD surgery. Although this feature did not affect outcomes in our study cohort, it needs to be borne in mind for avoiding excessive flocculus retraction, especially by less experienced surgeons. Clinical trial number Not applicable.
用于治疗面肌痉挛（HFS）的微血管减压术（MVD）需要牵拉小脑绒球，以监测面神经根部出口区（REZ）是否存在任何神经血管压迫。即便如此，由于绒球“大”或“肥厚”，在某些情况下识别神经血管压迫可能具有挑战性。我们经常遇到这样的病例，尽管MRI上绒球大小看起来正常，但REZ仍难以看清。因此，我们推测绒球与REZ之间的解剖关系而非绒球大小是影响REZ可视性的关键因素。在这项回顾性观察研究中，我们检查了HFS患者MVD术前MRI表现与REZ可视性之间的相关性。我们在三维图像中测量了绒球的大小，并评估其向内侧延伸的程度，即其内侧边界是否延伸至面神经REZ之外。通过回顾手术视频评估REZ的可视性。我们还使用分级评分检查了REZ可视性是否影响手术结果。该研究纳入了65例患者。53例患者在手术显微镜下成功观察到REZ，12例未观察到，绒球体积分别为0.37 ml和0.41 ml，组间差异无统计学意义（P = 0.23）。在这些病例中，分别有1例（1.9%）和5例（41.7%）观察到绒球向内侧延伸，差异有统计学意义（P = 0.0002）。MVD有效性（P = 0.88）或并发症（P = 0.41）在组间无显著差异。我们发现了一种新的解剖变异，即“绒球向内侧延伸”，这在MVD手术期间对面神经REZ的可视性有显著影响。尽管这一特征在我们的研究队列中未影响手术结果，但需要牢记这一点，以避免过度牵拉绒球，尤其是经验不足的外科医生。临床试验编号：不适用。
