3.0 T磁共振弥散张量成像评价单侧型急性腰椎间盘突出所致神经根损伤

EFFICACY OF 3.0 T MR DIFFUSION TENSOR IMAGING IN DIAGNOSING NERVE ROOT INJURY IN UNILATERAL ACUTE LUMBAR DISC HERNIATION

目的:探讨磁共振弥散张量成像(diffusion tensor imaging, DTI)和纤维示踪成像(fiber tractography, FT)技术在定量评价单侧型急性腰椎间盘突出所致神经根损伤的价值。方法:连续收集64例单侧型急性腰椎间盘突出症并椎间孔狭窄病人与30例健康志愿者,利用视觉模拟评分(visual analog scale, VAS)对病人进行疼痛学评分。采用3.0T磁共振扫描仪进行常规腰椎间盘检查以及L3、L4及L5神经根行磁共振弥散张量成像和纤维示踪成像。其中,DTI b值设为800 s/mm2,分别在DTI图像上测量各神经平均各向异性分数(fractional anisotropy, FA),在FT图像观察神经纤维束走行情况。分析病人VAS评分与受压侧神经根FA值的相关性。结果:所有腰椎间盘突出症病人和健康志愿者腰骶部神经根在DTI和FT图像上均清晰显示。健康志愿者左右两侧及不同层面之间神经根平均FA值比较均无统计学差异,L3-L5神经根平均FA值为0.199±0.025,FT图像上双侧神经根走行自然。而腰椎间盘突出病人受压侧神经根平均FA值为0.145±0.024,同层面对侧神经根平均FA值为0.201±0.026,受压侧神经根FA值明显低于健侧神经根,差异具有统计学意义(P <0.05)。FT显示患侧神经根不同程度受压、变窄以及纤维束断裂。急性腰椎间盘突出症病人疼痛VAS评分为7.82±1.23,与受压侧神经根平均FA值呈负相关(r=-0.728,P<0.05)。结论:DTI和FT可较好的显示和定量评价单侧型急性腰椎间盘突出所致的神经损伤,损伤侧神经根平均FA值显著降低。

Objective:To explore the significance of quantitatively evaluation in nerve roots injury using diffusion tensor imaging(DTI)and fiber tractography(FT)in patients with unilateral acute lumbar disc herniation.Methods:Sixty-four patients,with unilateral acute lumbar disc herniation and intervertebral foramen stenosis,and thirty healthy volunteers were enrolled in this study.Visual analogue scale(VAS)was used for pain assessment.Magnetic resonance scanner was used to perform routine lumbar intervertebral disc examination.Diffusion tensor imaging and fiber tractography were performed for L3-L5 nerve roots.The b value in DTI was set at 800 s/mm2,the fractional anisotropy(FA)value of the nerve was measured on DTI images,and the fiber bundle was observed in FT images.The correlation between the VAS score and the FA value of the injured nerve root was analyzed.Results:The lumbosacral nerve roots of all the patients and healthy volunteers were clearly visualized on DTI and FT images.There was no significant difference in the mean FA values between the left and right sides and different level of nerve in healthy volunteers.The mean FA value of L3-L5 nerve root was 0.199±0.025.FT imaging of bilateral nerve roots on the natural.Mean FA value of injured nerve root was 0.145±0.024 for patients with lumbar disc herniation,which was significantly lower than intact side in 0.201±0.026(P<0.05).Abnormalities of tractography were displayed for"Narrowing"and"Disrupted".The VAS score of pain in patients with acute lumbar disc herniation was 7.82±1.23,which was negatively correlated with the mean FA value of the nerve root in the injured side(r=-0.728,P<0.05).Conclusions:DTI and FT can quantitatively evaluate the nerve injury caused by unilateral acute lumbar disc herniation.The mean value of FA in the injured side significantly decreased.