视神经脊髓炎皮质脊髓束与胼胝体的DTI研究

Diffusion tensor imaging of the corticospinal tract and corpus callosum in neuromyelitis optica

目的利用扩散张量成像(DTI)研究视神经脊髓炎(NMO)患者脑白质纤维束扩散异常的发生机制。方法对19例脑MRI正常的NMO患者及19例性别和年龄匹配的正常志愿者进行DTI检查。重建出皮质脊髓束(CST)和胼胝体,并测量其平均扩散率(MD)、分数各向异性(FA)、最大本征值(λ1)和横向本征值(λ2-3)。然后,分析大脑脚、内囊和侧脑室水平CST感兴趣区(ROI)的扩散指标的异常变化。结果与正常志愿者比较,NMO患者CST的MD(P<0.001)和λ2-3(P=0.002)明显增加,而胼胝体的MD、FA、λ1和λ2-3均无显著变化(P>0.05)。在NMO患者,沿着CST的ROI分析显示在大脑脚和内囊水平CST的MD和λ2-3明显增高,FA轻度降低,而λ1无显著变化。在侧脑室水平CST的所有扩散指标均无显著变化。结论NMO患者脑白质纤维束表现为局部受累模式。继发于脊髓病灶的逆行性变性可能是NMO患者CST扩散异常的原因。

Objective To investigate the pathogenesis of the abnormal diffusion in the white matter tracts in patients with neuromyelitis optiea （NMO） using diffusion tensor imaging （DTI）. Methods Nineteen NMO patients with normal brain MRIs were prospectively studied with DTI and quantitatively compared with 19 sex-and age-matched healthy controls. The corticospinal tract （CST） and corpus callosum were reconstructed by the streamline method of tractography and analyzed using mean diffusivity （MD）, fractional anisotropy （FA）, primary （λ1） and transverse eigenvalue （λ2-3）. Region of interest （ROI） based analysis of diffusion indices was subsequently performed along the CST at the levels of the cerebral peduncle, internal capsule and lateral ventricle. Results Compared with healthy controls, NMO patients had significant increases in MD （P〈0. 001） and λ2-3 （P=0. 002） of the CST, but no significant changes in MD, FA, λ1 and λ2-3 of the corpus callosum （P〉0. 05）. ROI measurements along the CST in patients with NMO revealed significant increases in MD and λ2.3, slight decreases in FA, and no significant changes in λ1 at the levels of the cerebral peduncle and internal capsule. However, the CST at the level of the lateral ventricle showed no significant changes in MD, FA, λ1 and λ2-3. Conclusion NMO patients show a local involvement pattern in the white matter tracts. Retrograde degeneration secondary to lesions in the spinal cord may explain the diffusion abnormalities of the CST in patients with NMO.