Brain Tumor Clinic and Gamma Knife Center, Department of Neurosurgery, Chonnam National University Research Institute of Medical Sciences, Chonnam National University Hwasun Hospital and Medical School, Hwasun-gun, Jeollanam-do, South Korea.
Brain Tumor Clinic and Gamma Knife Center, Department of Neurosurgery, Chonnam National University Research Institute of Medical Sciences, Chonnam National University Hwasun Hospital and Medical School, Hwasun-gun, Jeollanam-do, South Korea.
World Neurosurg. 2019 Oct;130:410-414. doi: 10.1016/j.wneu.2019.07.119. Epub 2019 Jul 23.
Hemifacial spasm (HFS), one of the most common hyperactive cranial rhizopathies, is a disorder characterized by spontaneous, intermittent, and repetitive contraction of unilateral facial muscle. The most common cause of HFS is a mechanical compression of the facial nerve at the root exit zone (REZ) by blood vessels located in the brainstem. The incidence of cerebellopontine angle (CPA) tumor-induced HFS ranges from 0.3%-2.5% of all patients with HFS, and the incidence of epidermoid cyst among such tumors is extremely rare (0.2% to 0.25%). We present a patient manifesting HFS induced by a small epidermoid cyst who underwent Gamma Knife surgery (GKS) for ipsilateral vestibular schwannoma (VS) more than 10 years ago.
A 59-year-old female was admitted to our hospital with HFS. Ten years before admission, the patient underwent GKS for ipsilateral VS. Enhanced brain magnetic resonance imaging demonstrated that the volume of VS was not increased. Also, no definitive mechanical compression of the facial nerve REZ by blood vessels was detected. We concluded that HFS was secondary to the VS treatment by GKS and decided to operate to remove the tumor and identify REZ. A standardized lateral suboccipital retrosigmoid approach was performed. The cochlear nerve was encased by a tumor mass, and the posterior inferior cerebellar artery (PICA) was displaced by the mass. During tumor excision, we ensured that the VS and displaced PICA did not directly compress the REZ. Interestingly, an unexpected lesion was found with a yellowish viscous mass located between the sixth nerve and ventral side of the seventh nerve REZ. After the tumor removal, a small piece of Teflon was inserted between the PICA and REZ of the facial nerve. Postoperatively, the patient experienced no HFS or facial nerve dysfunction. Histopathologic examination of the lesion revealed an epidermoid cyst.
We should consider various possibilities for the cause of HFS and review brain imaging meticulously if patients were treated for CPA tumor with GKS a long time ago and the delayed HFS occurred without changes in tumor volume. HFS induced by epidermoid cyst is rare. Therefore it is critical for the neurosurgeon to ensure the absence of any abnormal contact with the REZ of the facial nerve during surgery for HFS induced by CPA tumors.
面肌痉挛（HFS）是最常见的颅神经根活性疾病之一，是一种以单侧面部肌肉自发性、间歇性和重复性收缩为特征的疾病。HFS 最常见的原因是血管位于脑干的面神经根部出口区（REZ）对面神经的机械压迫。桥小脑角（CPA）肿瘤引起的 HFS 发生率占所有 HFS 患者的 0.3%-2.5%，而此类肿瘤中的表皮样囊肿发生率极低（0.2%至 0.25%）。我们报告了一例由小表皮样囊肿引起的 HFS 患者，该患者 10 多年前因同侧前庭神经鞘瘤（VS）接受了伽玛刀手术（GKS）。
一名 59 岁女性因 HFS 入院。入院前 10 年，患者因同侧 VS 接受 GKS 治疗。增强脑磁共振成像显示 VS 体积无增加。此外，也没有发现血管对面神经 REZ 的明确机械性压迫。我们认为 HFS 是 GKS 治疗 VS 的结果，并决定手术切除肿瘤以识别 REZ。采用标准的侧枕下乙状窦后入路。耳蜗神经被肿瘤包裹，小脑后下动脉（PICA）被肿瘤移位。在肿瘤切除过程中，我们确保 VS 和移位的 PICA 不会直接压迫 REZ。有趣的是，在第六神经和第七神经 REZ 的腹侧之间发现了一个意想不到的病变，有一个黄色粘性肿块。肿瘤切除后，在 PICA 和面神经 REZ 之间插入一小块特氟隆。术后，患者未出现 HFS 或面神经功能障碍。病变的组织病理学检查显示为表皮样囊肿。
如果患者很久以前因 CPA 肿瘤接受 GKS 治疗，且延迟发生的 HFS 没有肿瘤体积变化，我们应考虑 HFS 病因的各种可能性，并仔细检查脑部影像学。由表皮样囊肿引起的 HFS 较为罕见。因此，对于神经外科医生来说，在因 CPA 肿瘤引起的 HFS 手术中，确保面神经 REZ 没有任何异常接触是至关重要的。
