患者女，29岁，间断性头晕8个月余，休息后可缓解，伴双眼视物模糊，无发热、恶心、呕吐，头痛等，近三天头晕症状加重，休息后不能缓解，遂来本院就诊，神经系统专科查体：神志清，GCS评分15分，查体合作，自动体位，言语清晰，记忆力、理解力、定向力检查未见异常。自诉嗅觉无异常。双眼视力视野正常，双眼裂等大，眼睑无下垂，双眼球向各方向活动正常，双侧瞳孔等大等圆，直径约3 mm，对光反射存在。四肢肌张力正常，右侧肢体肌力5级，左侧肢体肌力5级，四肢未见肌肉萎缩及震颤。双下肢巴氏征阴性。实验室检查未见明显异常。MRI平扫：右侧侧脑室三角区可见一大小约51.5 mm×44.8 mm×72.9 mm囊实性占位，边界较清，T1WI示实性部分呈不均匀略低信号，内可见多发小囊样低信号区，囊性部分呈低信号，并可见多发线、环样等信号分隔（图1A)，致右侧脑室后角明显扩大，邻近右枕顶叶受压，中线结构左偏，胼胝体部分中断，病变周围可见轻度水肿影；T2WI示病灶实性成分呈不均匀稍高信号，内可见多发小囊样高信号区，囊性部分呈高信号，并可见多发线、环样等信号分隔（图1B~D)；扩散加权成像（diffusion weighted imaging，DWI)示肿瘤实性部分呈略高信号，囊性部分呈低信号（图1E)，增强扫描病灶实性部分明显强化，内多发小囊变区无强化，囊性部分囊壁及分隔轻度强化，右侧脑室脉络丛与病灶关系密切并推挤前移、明显强化（图1F、G)。磁共振波谱（magnetic resonance spectroscopy，MRS）示病灶实性部分N-乙酰天门冬氨酸(N-acetylaspartic acid ，NAA）峰缺失，胆碱（choline，Cho）峰升高，并可见肌酸峰（creatine，Cr)（图1H)。术前MRI诊断：右侧侧脑室三角区囊实性占位，考虑脉络丛乳头状瘤或室管膜瘤。

       术中所见：肿瘤位于右侧脑室三角区，色灰白，形态不规则，质地韧，血管一般，与周围脑组织界限欠清，分块切除肿瘤，见肿瘤与脉络丛联系密切。病理结果：（侧脑室)神经鞘瘤（图1I)。免疫组化染色：瘤细胞示S-100 (+)、GFAP(-)、EMA (-)、Vimentin (+)、CK广(-)、CD34（血管＋)、Bcl-2(-)、h-caldesmon(-）、Desmin(-）、TLE1(-）、STAT6(-），ki67阳性细胞数1%～2%。

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图1  女，29岁。A：T1WI示右侧侧脑室三角区可见一囊实性占位，实性部分呈不均匀略低信号，内可见多发小囊样低信号区，囊性部分呈低信号，并可见多发线、环样等信号分隔，致右侧脑室后角明显扩大，邻近右枕顶叶受压，中线结构左偏，胼胝体部分中断，病变周围可见轻度水肿影；B～D： T2WI示病灶实性成分呈不均匀稍高信号，内可见多发小囊样高信号区，囊性部分呈高信号，并可见多发线、环样等信号分隔；E：DWI示肿瘤实性部分呈略高信号，囊性部分呈低信号；F、G：增强扫描病灶实性部分明显强化，内多发小囊变区无强化，囊性部分囊壁及分隔轻度强化，右侧脑室脉络丛与病灶关系密切并推挤前移、明显强化；H：MRS示病灶实性部分NAA峰缺失，Cho峰升高，可见肌酸(Creatine，Cr）峰；I：病理图片示梭形细胞稀疏不均排列，局部可见栅栏状排列，未见明显异型性
Fig. 1  A 29-year-old female patient. A: T1WI showed a solid-cystic tumor in the right trigone of the lateral ventricle, the solid part of the tumor showed an uneven slightly hypointense, multiple microcystoid hypointense regions can be seen in the region, the cystic part showed hypointense, it is also seen that the multiple lines are separated by isointensity, the posterior horn of the right ventricle is markedly enlarged, adjacent right occipital parietal lobe is compressed, the center line is deviated to the left, the corpus callosum is interrupted, slight edema can be seen around the tumor. B-D: T2WI showed that the solid part of the lesion showed slightly hyperintensity, multiple microcystoid hyperintense areas can be seen in the region, it is also seen that the multiple lines are separated by equal signals. E: DWI showed the solid part of the tumor showed slightly hyperintensity, while the cystic part showed hypointense, the choroid plexus of the right ventricle is closely related to the tumor and is pushed forward, which is obviously enhanced. F, G: CE-T1WI showed the solid part of the lesion was obviously enhanced, but there was no enhancement in the polycystic area and in the cystic part. H: MRS showed that the solid part of the lesion was missing NAA peak and the Cho peak was increased, creatine peaks are visible. I: Pathological images showed sparse and uneven arrangement of spindle cells, with local palisade arrangement, but no obvious atypia.

讨论

       神经鞘瘤起源于组成神经鞘膜的雪旺氏细胞，占颅内肿瘤的8%，80％位于桥小脑角区，好发于颅神经，以前庭神经（听神经瘤）和三叉神经（三叉神经鞘瘤）最为常见，其他少见发生部位包括：面神经，后组颅神经及前颅窝底^[1]。通常情况下中枢神经系统内神经纤维无雪旺氏细胞包裹，故将发生于脑实质或侧脑室的非颅神经主干的神经鞘瘤称作异位神经鞘瘤，非常罕见，国内外报道经病理证实的原发脑室内神经鞘瘤约为30余例^[2,3]。查阅文献［4，5，6，7]，其起源仍不清楚，目前有四种学说：(1)血管周围脉络丛的自主神经组织肿瘤转化；(2)组织损伤后多潜能间充质细胞转化为雪旺氏细胞；(3）胚胎发育异常时神经嵴细胞的异位碎片向脑室系统的肿瘤转化；(4 )脑内中胚层来源的间质软脑膜细胞可能转变为雪旺氏细胞。而本例发生于右侧脑室三角区，术中见与脉络丛联系密切，多考虑起源于血管周围脉络丛的自主神经组织肿瘤转化。

       本例术前误诊，主要原因在于发生于非颅神经主干的神经鞘瘤非常罕见，其影像表现也不具有特异性，所以，对于30岁左右中青年人，发生侧脑室内囊实性占位，DWI序列呈等或略高信号，增强后实性部分明显强化，在诊断中不应完全排除神经鞘瘤的可能。但最终诊断要依据病理，结合特异性免疫组化染色S-100和vimentin强阳性表达，可以明确诊断。