Objective:To analyze the MRI features of brain pleomorphic xanthoastrocytomas ( PXA ) in 8 cases for improving its clinical,pathological and MRI features understanding. Methods:The MRI plain scans, enhanced scans and DWI were explored in 8 cases with brain PXA diagnosed by pathology,and the MRS combined with PWI were examined in 2 cases. Results:Three patients were male and 5 patients were female,the age of all patients ranged from 14 to 56 years old(including 6 patients less than 25 years old). Interstitial change in 2 cases were found. Single lesion in 7 cases and single lesion complicated with round multiple lesions in 1 case with interstitial change were found. Five cases located or involved in temporal lobe,6 cases located in the cortex and subcortical region. Solid-cystic tumors in 5 cases and solid tumors in 3 cases( including 1 case with partial pia mater invasion,1 case with bleeding and ependymal invasion and 1 case with lateral ventricle spread) were identified by MRI. The tumor solid area showed slightly hypointense on T1-weighted images, slightly hyperintense on T2-weighted images and marked enhancement. The difference between the apparent diffusion coefficient value and subcortex alba was not statistical significance(P>0. 05). The solid-cystic capsule wall enhanced in 2 cases. The light to moderate degree edema around the tumor were detected in all tumors. The significant increasing Cho peak and decreasing N-acetyl aspartic acid peak and Lip peak were found in tumor solid area with high perfusion. Conclusions:PXA occurres usually in adolescent,which locates the brain shallow position of the temporal lobe. The tumor pathologic and genetic characteristics are different from other astrocytomas, complete surgical excision is important for a good prognosis. The conventional magnetic resonance imaging,magnetic resonance perfusion weighted imaging and magnetic resonance spectroscopy of PXA have certain characteristics.%目的：提高对脑多形性黄色星形细胞瘤( PXA)临床、病理及MRI特征的认识。方法：回顾性分析8例PXA的MRI表现并复习相关文献,8例脑PXA均经病理证实,均行MRI平扫、增强扫描及扩散加权成像,2例行多体素磁共振波谱( TE135ms)和灌注加权成像检查。结果：8例PXA年龄14~56岁,25岁以下者6例。伴间变特征者2例。7例单发,1例伴间变特征者为单发肿块伴周围子灶。5例发生或累及颞叶,6例位于皮层及皮层下。 MRI表现5例呈囊实性,3例呈实性,1例伴局部软脑膜受侵,1例伴出血及室管膜受侵(伴间变特征),1例伴侧脑室播散(伴间变特征)。肿瘤实性区均呈明显强化的稍长T1稍长T2信号,扩散加权成像呈等或稍高信号,表观扩散系数值与正常皮层下脑白质差异无统计学意义(P>0.05)。2例囊实性者囊壁强化。所有肿瘤周围均有轻到中度水肿。2例肿瘤实性区呈高灌注,胆碱峰明显升高,N-乙酰天门冬氨酸峰明显下降,多见乳酸峰。结论：PXA好发于青少年,多发生于幕上脑浅部,多位于颞叶,其病理学及遗传学特征有别于其他星形细胞瘤,肿瘤全切是预后的主要保证。 PXA的常规MRI、磁共振灌注加权成像和磁共振波谱具有一定特点。
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