迷走神经鞘瘤(Vagal Schwannoma (Path proven) )CT-MRI病例图片影像诊断分析周围神经 2010-11-01
【临床病史】：患者，57岁男性出现右侧下颌下腺隆起。57-year-old male with right sided swelling of the submandibular gland
【影像表现】：Figure 1, Figure 2, and Figure 3: Contrast enhanced axial CT images through the neck demonstrate a 4.5 X 6 cm circumscribed and moderately enhancing mass within the right carotid space with scattered areas of low density centrally within the mass (blue arrows). The internal and external carotid arteries (green arrows) as well as the parapharyngeal fat (red arrow) are displaced anteriorly. The parotid gland is separate from the lesion (purple arrow).
Axial and coronal T2 weighted images (Figure 4 and Figure 5) and axial and coronal T1 weighted post-gadolinium fat saturated images (Figure 6 and Figure 7) again show a well defined mass with heterogeneous T2 signal and areas of cystic degeneration (blue arrows). There is peripheral enhancement following gadolinium administration (orange arrows). Note that the mass is not contiguous with the parotid gland (purple arrows).
【影像诊断】：Vagal Schwannoma (Path proven) 迷走神经鞘瘤
【诊断要点】：Vagal schwannomas are benign tumors that may present with hoarseness or cough, however the majority of patients are asymptomatic. 迷走神经鞘瘤是一种良性肿瘤，可以表现为声音嘶哑或咳嗽，然而大部分病人没有症状。
Schwannomas of the vagus nerve need to be differentiated from paragangliomas because the distinction may influence treatment planning 迷走神经鞘瘤需要与副神经节瘤相鉴别，其差异可能影响治疗计划。
【讨论】：Schwannomas are benign neoplasms which arise from the nerve sheath and consist of schwann cells in a collagenous matrix. Histologically, the terms Antoni type A and Antoni type B are used to describe varying growth patterns. Type A tissue has elongated spindle cells and is compact in nature while type B has a looser organization with cystic spaces intermixed within the tissue. These cystic spaces result in high signal intensity on T2 weighted MR sequences.
神经鞘瘤是一种良性肿块，起源于神经鞘，在其胶原基质内包含有许旺氏细胞。在组织学上，术语Antoni A型和Antoni B型被用于描述不同的生长方式。A型组织有狭长的梭形细胞并且结构致密，而Antoni B型有一个疏松的结构，组织内混合有囊性间隙。这些囊性间隙导致在MRT2序列上呈高信号。
Vestibular schwannomas are the most common cranial nerve (CN) schwannoma, followed by trigeminal and facial and then glossopharyngeal and vagus schwannomas. CN schwannomas are usually isolated lesions, except when they are associated with neurofibromatosis type 2 (NF2). NF2 is characterized by bilateral acoustic schwannomas but other CN schwannomas also occur at an increased frequency in these patients.
The majority of carotid space masses are benign, with the two most common lesions being the vagus schwannoma and the glomus tumor. Neoplasms of the vagus nerve include paragangliomas (50%), schwannomas (31%), neurofibromas (14%), and neurofibrosarcomas (6%). Most cases of schwannomas manifest between the third and sixth decades of life as a firm and painless mass in the neck.
Schwannomas of the vagus nerve are usually well-defined, rounded structures which are hypodense to muscle on CT and enhance moderately. On MR, there is variable T2 signal intensity depending on its content of Antoni A and Antoni B tissue. Hemorrhage and cystic degeneration are not uncommon. They result in anterior displacement of the carotids. In contrast, glomus tumors are highly vascular and demonstrate dramatic enhancement. Flow voids are usually visualized, resulting in the characteristic salt-and-pepper appearance. Carotid body tumors tend to splay the internal and external carotid arteries away from each other, while glomus vagale tumors displace the carotid artery anteriorly. The distinction between a vagus schwannoma and the glomus vagale tumor has to be made on the basis of flow voids and vascular flow curves. Also, glomus vagale tumors are relatively uncommon.
迷走神经鞘瘤通常边界清楚、类圆形结构，与肌肉密度相比呈低密度，中度强化。在MRI上，以及其内Antoni A和Antoni B型组织的内容不同其T2表现为不同的信号强度。出血和囊变并非罕见。肿块导致颈动脉前移，增强扫描，血管球瘤是富血供的、明显强化。常常可以看见流空信号，导致特征性的胡椒拌盐征。颈动脉体瘤倾向于扩大分离颈内外动脉，而迷走神经血管球瘤向前推移颈动脉。迷走神经鞘瘤和血管球瘤之间区别基于流空和血管流量，同时迷走神经血管球瘤是相对少见的。(参考来源:,ACR Friday, July 17, 2009,作者:freemanpyw译)