椎管内脊膜囊肿的低场磁共振成像分析

Spinal meningeal cyst:analysis with low-field MRI

目的分析椎管内脊膜囊肿在低场磁共振的MR表现,并对其分类与分型、临床症状、MRI表现及诊断与鉴别诊断进行讨论。方法本组42例均行0.35T永磁型磁共振矢状面T_1WI、T_2WI和横断面T_2WI及部分患者加行轴位T_1WI,12例行MR增强扫描。结果按Nabors方法分为:椎管内硬膜外脊膜囊肿(Ⅰa型)4例,骶管内脊膜囊肿(Ⅰb型)32例,根性囊肿(Ⅱ型)4例,椎管内硬膜下脊膜囊肿(Ⅲ型)2例。椎管内脊膜囊肿均边界清楚,T_1WI均匀低信号,T_2WI均匀高信号,与脑脊液相似,12例增强扫描均无强化。Ⅰa型常位于中下段胸椎脊髓背侧,并脊髓受压、硬膜外脂肪推移。Ⅰb型位于骶管内,与硬脊膜囊之间有脂肪相隔。Ⅱ型位于硬脊膜囊侧方,其内有神经根存在。Ⅲ型囊肿常位于胸段脊髓背侧,脊髓受压、前移和变形。结论低场MRI能较好地显示椎管内脊膜囊肿,对椎管内脊膜囊肿的定位和定性诊断提供影像依据,Ⅰa型及Ⅰb型椎管内脊膜囊肿MR征象较典型,诊断不难;而根性囊肿及硬膜下脊膜囊肿需要与囊性神经鞘瘤及肠源性囊肿鉴别。

Objective To analyze the characteristics of spinal meningeal cyst in low-field MRI and to discuss its classification, subtype, clinical presentation, and differential diagnosis. Methods Forty-two patients （20 male, 22 female） were examined with sagittal T1- and T2-, axial T2-weighted MR imaging. Twelve patients were also examined with contrast-enhanced MRI. Results The cysts were classified using Nakors＇ classification as type Ia extradural meningeal cysts （4 patients） , type Ib sacral meningeal cysts （32）,type II extradural meningeal cysts with spinal nerve root fibers （4）, and type III spinal intradural meningeal cysts （2）. All 42 spinal meningeal cysts had well-defined boundaries with low T, and high T2 signal intensities similar to cerebral spinal fluid. In type Ia, the lesions were often on the dorsum of mid-lower thoracic spinal cord compressing the spinal cord and displacing the extradural fat. In type lb, the lesions were in the sacral canal with fat plane between the cyst and dural sac. In type If, the lesions contained nerve roots and were lateral to the dural sac. In type III, the lesions were often on the dorsum of spinal cord compressing and displacing the spinal cord anteriorly. Conclusion Low-field MRI can clearly display the spinal meningeal cyst. Types Ia and Ib spinal meningeal cysts had typical features and can be easily diagnosed. Types lI and IIl should be differentiated from cystic schwannomas and enterogenous cysts, respectively.