臂丛神经鞘瘤的MRI诊断

MRI diagnosis of neurilemmoma of the brachial plexus

目的探讨磁共振成像(magnetic resonance imaging,MRI)在臂丛神经鞘瘤诊断中的应用价值。方法分析36例经手术和病理证实的臂丛神经鞘瘤术前MRI表现。观察内容包括病变部位、肿块大小、边界、信号、强化特征及范围。结果MRI能清晰显示臂丛神经的根、干及分支,表现为线状低信号影。36例臂丛神经鞘瘤平均直径为4．9cm,均表现为沿臂丛神经根生长的肿块,其中30例表现为边界清楚的纺锤形或长圆形肿块。MRI显示,16例表现为均匀的T_1WI低或等信号(与肌肉相比),T_2WI高信号,增强后中等度强化；20例T_1WI呈低信号,T_2WI呈不均匀高信号,内见低信号区,所谓的“靶征”,增强后明显强化。结论臂丛神经鞘瘤具有特征性的发生部位、形态学表现及MRI信号特点,对本病能提供准确的诊断依据。

Objective To investigate the value of magnetic resonance imaging （MRI） in the diagnosis of neurilemmoma of the brachial plexus. Methods Preoperative MRI images of 36 consecutive cases of neurilemmomas of the brachial plexus, proven surgically and pathologically, were reviewed. The MRI findings were analyzed for location, size, margin, signal intensity, contrast enhancement of the mass, and the extent of the lesions. Results The roots, trunks, and various divisions of the brachial plexus appeared as linear structures with low signal intensity on MR images obtained with all sequences. All patients had large sehwannomas （ mean size 〉 4.9 cm in diameter） presenting as masses along a brachial plexus nerve root as explored by MRI. 30 cases of the masses exhibited spindle or oblong shape with well-defined margins. 16 cases appeared as homogeneous hypo- or iso-intense to muscle in T1- weighted images, hyper-intense in T2-weighted images, and moderate contrast enhancement after administration of contrast media. 20 lesions were hypo-isointense to muscle on T1-weighted images and heterogeneous hyper-intense on T2-weighted images which may have central areas with low signal intensity, the so-called ＂target sign＂, and enhance intensely after administration of gadolinium-based contrast material. Conclusion The locations, morphologic features and MR signal characteristics are useful in making a proper preoperative diagnosis of neurilemmomas of the brachial plexus.