Carvalho Gustavo A, Matthies Cordula, Osorio Enrique, Samii Madjid
Department of Neurosurgery, State University of Rio de Janeiro, and Clinica Bambina, Rio de Janeiro, Brazil.
Neurosurgery. 2003 Apr;52(4):944-8; discussion 948-9. doi: 10.1227/01.neu.0000053100.29308.f3.
To highlight the clinical, radiological, and surgical findings and therapeutic options for this rare entity, which may mimic a purely intrameatal vestibular schwannoma, and to define the particular aspects of preoperative differential diagnosis and surgical management.
Two patients presented with clinical findings typical of vestibular schwannomas, i.e., tinnitus, hearing loss of 30 dB, and an intrameatal contrast-enhancing lesion on magnetic resonance imaging studies.
The lesions were exposed via a suboccipital transmeatal approach, and tumor infiltration of the cochlear and/or facial cranial nerves was identified. In view of the unclear intraoperative histology, surgical management was based on criteria of cranial nerve function. In Patient 1, after nerve decompression by subtotal tumor removal, preserved auditory brainstem responses and facial nerve electromyography indicated functional nerve preservation and facilitated the decision for partial resection. In Patient 2, minimal tumor dissection resulted in complete loss of auditory brainstem response without reversibility. Therefore, a radical tumor removal was performed that sacrificed the cochlear but preserved the facial nerve.
Symptoms and signs of internal auditory canal hamartomas are congruent with other typical pathological lesions of the internal auditory canal and cerebellopontine angle. Accurate preoperative diagnosis by radiological means is not possible, but careful evaluation of the different signal intensities on magnetic resonance imaging studies may indicate this rare pathological condition. Intraoperative surgical findings of tumor infiltration of the faciocochlear cranial nerve complex may support simple observation. In view of the nonneoplastic characteristic of these lesions, a more conservative approach is justified. The decision should be based on the functional status of the cranial nerves, for which reliable electrophysiological monitoring is indispensable.
强调这种可能酷似单纯内耳道前庭神经鞘瘤的罕见疾病的临床、放射学及手术发现和治疗选择，并明确术前鉴别诊断及手术管理的特殊方面。
两名患者呈现出前庭神经鞘瘤的典型临床表现，即耳鸣、30分贝的听力损失以及磁共振成像研究显示的内耳道强化病灶。
通过枕下经耳道入路暴露病灶，确定肿瘤对耳蜗和/或面神经的浸润情况。鉴于术中组织学不明确，手术管理基于颅神经功能标准。在患者1中，通过次全肿瘤切除进行神经减压后，保留的听觉脑干反应和面神经肌电图表明神经功能得以保留，有助于做出部分切除的决定。在患者2中，少量肿瘤切除导致听觉脑干反应完全丧失且不可逆转。因此，进行了根治性肿瘤切除，牺牲了耳蜗但保留了面神经。
内耳道错构瘤的症状和体征与内耳道及桥小脑角的其他典型病理病变一致。通过放射学手段进行准确的术前诊断是不可能的，但仔细评估磁共振成像研究中的不同信号强度可能提示这种罕见的病理状况。术中发现肿瘤浸润面听神经复合体可能支持单纯观察。鉴于这些病变的非肿瘤特性，更保守的方法是合理的。决策应基于颅神经的功能状态，对此可靠的电生理监测不可或缺。
