桥小脑角区少见病变的MRI表现和病理对照研究

MRI Findings of Rare Lesions in the Cerebellopontine Angle:Comparison with Pathological Results

目的探讨桥小脑角区少见病变的MRI表现,提高MRI对该区域少见病变的诊断准确性。资料与方法回顾性分析26例经病理证实的桥小脑角区少见病变的MRI表现并和病理作对照分析。结果 26例病变中,脉络丛乳头状瘤5例,原始神经外胚叶肿瘤(PNET)4例,海绵状血管瘤、血管外皮瘤、动脉瘤各3例,转移瘤4例,内淋巴囊瘤2例,皮样囊肿、骨孤立性浆细胞瘤各1例。右侧桥小脑角区16例,左侧10例;位于桥小脑角池9例,起自脑内或脑室累计桥小脑角11例,起自脑外颅底6例。脉络丛乳头状瘤可原发于桥小脑角或由第四脑室侵入,多表现为菜花状,中度或明显强化;皮样囊肿在扩散加权成像(DWI)上呈高信号,无强化;动脉瘤瘤体呈流空信号或周边环形流空信号,与邻近血管一致的强化;PNET以实性为主,DWI呈高信号,中度到明显强化;海绵状血管瘤在T1WI、T2WI上均呈混杂信号,瘤周见低信号环;血管外皮细胞瘤呈分叶状并与硬膜窄基底相连,瘤内常见坏死和流空血管,增强后明显强化;内淋巴囊瘤和髓外浆细胞瘤均表现肿块伴颅底骨质破坏,前者信号混杂,后者信号较均匀;转移瘤多有原发恶性肿瘤史,单发或多发,可位于脑内,也可位于脑外,MRI表现缺乏特征性。和手术及病理对照,MRI定位、定性诊断准确率分别为88%、54%。结论桥小脑角区少见病变种类繁多,MRI能准确显示病变的位置和起源;病变MRI表现复杂,但多数仍有其特征性,仔细分析其MRI征象结合其定位,能够术前确诊,少数诊断困难,可加深对它们的认识。

Objective To investigate the MRI features of rare lesions in the cerebellopontine angle（CPA）,so as to improve the diagnostic accuracy.Materials and Methods The MRI manifestations of 26 rare lesions in CPA confirmed by pathology were analyzed retrospectively.Results The rare lesions in CPA included choroid plexus papilloma in 5 cases,primitive neuroectodermal tumors（PNET） in 4 cases,cavernous hemangioma,hemangiopericytoma and aneurysm in 3 cases each,metastatic tumor in 4 cases,endolymphatic sac tumor in 2 cases,dermoid cyst,solitary plasmacytoma of bone in 1 case each.16 cases located at right CPA and 10 cases located at left.9 cases were in the CPA cistern.11 cases of intracephalic or intraventricular lesions invaded the CPA.6 cases rised from the skull base.Choroid plexus papilloma（n=5） may rise from CPA cistern or fourth ventricle and extend into CPA.The tumors showed cauliflower-like shape and moderate to marked enhancement.Dermoid cyst（n=1） appeared hyperintense on DWI and no enhancement.Aneurism（n=3） showed a flow void signal or peripheral ring flow void with heterogeneous enhancement after contrast media injection.Primitive neuroectodermal tumors（n=4） showed solid tumors and appeared hyperintense on DWI and moderate to marked enhancement.Cavernous hemangioma（n=3） appeared as mixed signal intensity lesions surrounded by a peripheral rim of hypointensity on all sequences.Hemangioperithelioma（n=3） demonstrated an obviously enhanced lobulated lesion,attached to the petrous dura with a narrow base.Necrosis and flow viod vessels were common in tumors.Both endolymphatic sac tumours（n=2） and solitary plasmacytoma of bone（n=1） appeared mass like lesions assoiated with bone erosion.But the former had mixed signal,the latter was more homogeneous.Metastases appeared single or multiple,intra-or extracephalic,usually with a known cancer history.metastatic tumors lacked distinctive features on MRI.Compared with pathological results,the accuracy rates of level diagnosis and qualitative diagnosis by MRI were 88% and 54% respectively.Conclusion Rare lesions in the CPA areas showed variety on MR.MRI is valuable of demonstrating the location and origin of the lesions accurately,which lead to diagnosis and therapy.These lesions had complicated MRI appearance,but characteristics can be excavated in majority.Analysing the features carefully,will achieve preoperative accurate diagnosis.