Ozaki Ko, Higuchi Yoshinori, Nakano Shigeki, Horiguchi Kentaro, Yamakami Iwao, Iwadate Yasuo
1Department of Neurological Surgery, Chiba University Graduate School of Medicine, Chiba, Japan; and.
2Department of Neurosurgery, Seikeikai Chiba Medical Center, Chiba, Japan.
J Neurosurg Case Lessons. 2022 Apr 11;3(15). doi: 10.3171/CASE2275.
Hemifacial spasm (HFS) due to an arachnoid cyst at the cerebellopontine angle is rare. Here, the authors reported such a case and analyzed the mechanism of facial nerve hyperactivity by reviewing the literature.
A 40-year-old man presented with right HFS for the past 3 years. Preoperative magnetic resonance imaging revealed a right cerebellopontine angle cystic mass with high intensity on T2-weighted images, low intensity on T1-weighted and diffusion-weighted images, and no contrast effects. Cyst excision and decompression of the facial nerve using a lateral suboccipital approach to monitor abnormal muscle response (AMR) resulted in permanent relief. The cyst was histologically compatible with an arachnoid cyst.
In the present case, when the cyst was dissected, the AMR disappeared and no offending arteries were detected around the root exit zone. Therefore, the cyst itself was responsible for HFS, for which AMR was useful. Limited cases of HFS due to arachnoid cysts without neurovascular compression have been previously reported. The authors suggested that pulsatile compression by the cyst results in facial nerve hyperactivity and secondary HFS.
小脑脑桥角蛛网膜囊肿所致的半面痉挛（HFS）较为罕见。在此，作者报告了这样一例病例，并通过回顾文献分析了面神经功能亢进的机制。
一名40岁男性在过去3年中出现右侧HFS。术前磁共振成像显示右侧小脑脑桥角有一囊性肿块，在T2加权图像上呈高信号，在T1加权和扩散加权图像上呈低信号，且无强化效应。采用枕下外侧入路进行囊肿切除及面神经减压，并监测异常肌肉反应（AMR），结果痉挛得到永久性缓解。囊肿的组织学表现与蛛网膜囊肿相符。
在本病例中，当囊肿被分离时，AMR消失，且在神经根出口区周围未发现责任动脉。因此，囊肿本身是导致HFS的原因，而AMR在此过程中是有用的。此前已有关于无神经血管压迫的蛛网膜囊肿导致HFS的有限病例报道。作者认为囊肿的搏动性压迫导致面神经功能亢进及继发性HFS。
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