桥小脑角区表皮样囊肿侵犯毗邻神经血管的MRI研究

Epidermoid cyst in the cerebellopontine angle region invading adjacent neurovascular： a MRI study

目的 探讨MRI不同序列对观察桥小脑角区表皮样囊肿侵犯毗邻神经血管的优势.方法 回顾性分析经手术及病理证实的8例桥小脑角区表皮样囊肿的临床和MRI资料,比较T1WI、T2WI、FLAIR、DWI、T1增强扫描、3D-FIESTA及3D-TOF-MRA序列对桥小脑角区正常侧神经血管、表皮样囊肿及其侵犯神经血管的显示情况,重点评价3D-FIESTA和3D-TOF-MRA两种序列的优势.结果 常规MRI序列对颅底神经血管显示不佳;3D-FIESTA显示神经血管均清晰;3D-TOF-MRA显示动脉清晰,但显示颅神经不及3D-FIESTA.8例表皮样囊肿在3D-FIESTA中均呈等信号,且界限清楚;在3D-TOF-MRA中均呈低信号,与邻近脑脊液界限不清.3D-FIESTA均清晰显示8例病变对三叉神经的包绕（显示率100%）,其中4例三叉神经变细,2例折角变形;病变完全包绕面听神经3例,推压移位1例,紧密接触2例,未见接触2例.8例患者临床上均有三叉神经痛,其中4例为2、3支受累,其余4例为1、2、3支均受累,影像特征与临床表现符合;3例面听神经被包绕,其中1例临床表现有听力障碍.结论 3D-FIESTA能清晰显示桥小脑角区表皮样囊肿及其对邻近神经血管的侵犯情况,同时结合3D-TOF-MRA能够作出更为准确的术前评估.

Objective To explore the advantages of MR imaging sequences displaying the epidermoid cyst （EC） with adjacent neurovascular invasion in the cerebellopontine angle region.Methods Petrospective analysis on clinical and MR imaging data of 8 patients with ECs in the cerebellopontine angle region confirmed by surgery and pathology was performed. T1WI, T2WI, FLAIR,DWI, T1 enhancement scanning, and both 3D-FIESTA and 3D-TOF-MRA sequences, especially, were performed to investigate the normal neurovascular signal features, epidermoid cyst and its neurovascular invasion features in cerebellopontine angle region and the advantages of 3D-FIESTA and 3D-TOF-MRA sequences in demonsuating these features were analyzed too. Results Conventional sequences showed poor results on nerves and vessels, but 3D-FIESTA showed clear results. Vessels were clearly showed under 3D-TOF-MRA, but nerves shown under 3D-TOF-MRA were not as clear as those under 3D-FIESTA. Eight ECs showed isointensity in 3D-FIESTA, and the border of the lesions could be delineated clearly from peripheral CSF. However, hypointensity was showed in 3D-TOF-MRA, and the borders of the lesions could not be identified from CSF. All of the 8 patients with ECs （100%） showed trigeminal nerve encasement on 3D-FIESTA, including 4 thinning and 2 fold distortion. In the 8 patients with ECs, 3 （37.5%） showed facial and acoustic nerves encasement （1 was also diagnosed as having dysaudia by clinical manifestations）, 1 （12.5%） displacement, 2 （25%） tight relationship, and 2 （25%）non-touching. Clinically, all 8 patients with ECs had trigeminal neuralgia; of them, the 2nd and 3ndtrigeminal nerves were involved in 4 patients and the 1^st, 2^nd and 3^nd trigeminal nerves were all involved in the other 4 patients; the imaging features and clinical manifestations were 100% coincident. Conclusion 3D-FIESTA sequence is superior to other MR imaging sequences in demonstrating the ECs with neurovascular invasion; combined with 3D-TOF MRA, 3D-FIESTA can give precise preoperative evaluation.