鼻咽癌向后颅窝侵犯的途径及MRI表现

MRI Signs of Nasopharyngeal Carcinoma with the Involvement of the Posterior Cranial Fossa

目的 探讨鼻咽癌向后颅窝侵犯的途径及MRI表现特点。材料与方法 回顾性分析 35例鼻咽癌向后颅窝侵犯的病例。放疗前检查 12例 ,放疗后复发 2 3例。使用西门子 1.0T扫描仪 ,SE序列横轴位、冠状位T1WI、T2 WI ,矢状位T2 WI ,增强后 3个方位T1WI。全部病例经鼻咽腔活检确诊。后颅窝肿块 16例 ,10例手术切除 ,经斜坡直接向后颅窝侵犯形成肿块的 6例未手术。结果 (1)斜坡破坏 31例 ,6例在桥脑前池形成肿块。(2 )经舌下神经管侵犯 3例 ,左侧 2例有舌下神经管扩大 ,右侧 1例不扩大 ,3例颅内外肿块均经舌下神经管相连形成“哑铃”状。(3)中颅窝海绵窦肿块向后破坏颞骨岩尖部再向后侵犯后颅窝 5例。(4)经血行转移至右侧桥小脑角区脑膜 ,并在局部形成肿块 2例。(5 ) 2 5例伴有前中颅窝同时受侵犯。结论 鼻咽癌可通过破坏斜坡、经后颅窝自然通道、经血行转移至后颅窝的脑膜和中颅窝的肿块再向后侵犯等多个途径侵犯后颅窝 ,MRI能清楚。

Objective To study the routes invading the posterior cranial fossa by nasopharyngeal carcinoma (NPC) and the MRI features of the involvement.Materials and Methods MRI findings in 35 cases of biopsy-proved NPC with posterior cranial fossa (PCF) involvement, including 12 pre-radiotherapy cases and 23 post-radiotherapy cases, were retrospectively analyzed. Axial and coronal T 1WI and T 2WI, sagittal T 2WI and contrast-enhanced MRI were performed. Of 16 cases showing mass in the PCF, 10 were surgically removed.Results (1) 31 cases showed clivus involvement, 6 of which had mass in prepontile cistern. (2) Involvement via hypoglossal nerve canal was seen in 3 cases, presenting enlarged nerve canal in 2. The tumors demonstrated “dumbbell” appearance. (3) In 5 cases the tumors were at cavernous sinuses, destroying temporal bone posteriorly and spreading to PCF. (4) Hematogenous meningeal metastasis of cerebellopontine angle area was seen in 2 cases. (5) Both anterior and middle cranial fossae involvement was found in 25 cases.Conclusion NPC may spread to PCF by destroying clivus, via the natural bony canal or cavernous sinuses. MRI can well show the invading routes.