前屈-后伸位MRI对判断颅脊交界区畸形内固定指征的临床价值

目的分析前屈-后伸位MRI对诊断Arnold—Chiari畸形可能合并寰枢椎脱位的作用，以及指导治疗的临床意义。方法回顾分析40例Arnold—Chiari畸形患者的前屈-后伸位MRI影像学资料，测量寰齿间距，通过前屈位和后伸位颈椎椎管狭窄程度分级，判断颅脊交界区稳定性。单纯Arnold．Chiari畸形患者采用枕大孔减压和枕大池扩大成形术，存在寰枢椎脱位者兼行枕颈内固定融合术。结果经前屈．后伸位MRI检查，证实有12例患者存在颅颈失稳，于枕大孔减压的同时行枕颈内固定融合术。手术后第3天颈椎影像学检查，40例中10例脊髓空洞病灶明显缩小；12例兼行枕颈内固定融合术者颅颈复位满意，脊髓压迫解除；手术后3个月随访，脊髓空洞病灶明显缩小（17例），颅脊交界区骨痂形成、骨融合效果良好、颅颈复位无丢失（12例），日本矫形外科评分13．08±1．40，与手术前评分（11．08±1．61）比较，差异有统计学意义（t=5．928，P=0．000）。结论前屈．后伸位MRI对判断颅脊交界区稳定性、选择适宜的手术方式具有重要意义。

Clinical value of extension-flexion MRI in evaluating the indication of internal fixation for patients of craniovertebral junction malformation

Objective To analyse the value of cervical extension-flexion magnetic resonance imaging （EFMRI） in the evaluation of possible atlantoaxial dislocation （AAD） associated with Arnold-Chiari malformation. Methods Reviewed the image studies of 40 Arnold-Chiari malformation patients, including 19 females and 21 males. The cervical EFMRI was evaluated, atlantodental interval （ADI） was measured and spinal canal narrowing grade was evaluated to judge the instability of craniovertebral junction （CVJ）. The diagnostic criteria of instability of CVJ was that ADI increased more than 2 mm between flexion and the neutral or extention position in dynamic MRI, or the spinal canal stenosis grade increased more than one grade between flexion and the neutral or extention position in dynamic MRI. Foramen magnum decompression and cisterna magMa plasty were performed for the Arnold- Chiari malformation patients without instability of CVJ. For patients who were diagnosed instability of CVJ, occipitocervical internal fixation and fusion was indicated besides decompression. Results Twelve patients were diagnosed as instability of CVJ, and occipitocervical internal fixation and fusion, foramen magnum decompression and cisterna magMa plasty were performed. In the 40 patients, the syringomyelia of 10 patients shrinked on the MRI on the third day postoperatively. There was no movement of the instruments in 12 patients with internal fixation, and the spinal cord was well decompressed. Three months after surgery, the syringomyelia of 17 patients obviously shrinked in MRI. The bony bridge was demonstrated in CT in 12 cases. Japanese Orthopedic Association （JOA） score at 3 months after surgery was 13.08 ± 1.40, and was higher than that of preoperation signiflcantly （t = 5.928, P = 0.000）. Conclusion Cervical EFMRI has significant value in theevaluation of possible AAD in patients of Arnold-Chiari malformation, and can help to determine the surgical strategy.