改变颈椎屈曲角度对平山病特异性MRI征象的影响

MRI features of Hirayama disease at different cervical flexion angles

目的 比较平山病患者颈椎不同屈曲角度MRI表现,研究颈椎屈曲角度对平山病MRI征象的影响.方法 20例临床确诊为平山病的患者,行颈椎中立位及屈曲位20°、25°、30°、35°、40°MR扫描,观察不同屈曲位MRI硬脊膜前移、硬膜外间隙增宽2个征象出现率.并测量硬膜外间隙最大矢状径（d）及同水平椎管矢状径（D）,计算d/D用于定量分析上述2个征象.不同屈曲位各征象出现率的比较使用Fisher精确概率法.各组间d/D平均值比较使用重复测量资料方差分析,之后对任意两组间d/D平均值进行比较.结果 患者颈椎背侧硬脊膜前移及硬膜外间隙增宽征象出现率在屈曲角度20°时为70%（14/20）,25°以上均为100%,20°与25°时特殊征象出现率差异有统计学意义（χ^2=5.760,P=0.020）.20°、25°、30°、35°、40°时,对应d/D值分别为0.51±0.06、0.54±0.08、0.57±0.09、0.61±0.09、0.59±0.07,差异有统计学意义（F=3.450,P=0.013）,两两比较提示d/D平均值在屈曲35°时〉20°和25°,在屈曲40°时〉20°（P值均〈0.05）.结论 颈椎屈曲角度可以影响颈椎背侧硬脊膜前移及硬膜外间隙增宽的MRI征象.

Objective To analyze MRI features of different cervical flexion positions in Hirayama disease （HD） and discuss the effects on these features by different cervical flexion angles.Methods The cervical MR images of neutral and different flexion positions （20°, 25°, 30°, 35° ,40°） of 20 patients, who were clinically diagnosed as HD,were studied.At flexion positions, the appearance of anterior shifting of the posterior wall of the cervical dural canal and widening of epidural space was recorded.The maximum sagittal diameters （d） of widened cervical epidural space and the cervical canal sagittal diameters （D） on the same level were measured to calculate d/D value for quantitative evaluation of the two signs.Comparisons of appearance of the signs among different flexion positions were made using F/sher＇s exact test.Repeated measures analysis of variance （rmANOVA） was used to compare mean d/D values among groups with different positions, and paired comparisons were also performed.Results The appearance of anterior shifting of the posterior wall of the cervical dural canal were different between 20° group （70%, 14/20） and other 4 larger angles groups （100%） （χ^2 =5.76, P=0.020）.The d/D values were 0.51±0.06,0.54±0.08,0.57±0.09,0.61±0.09,0.59±0.07 respectively at abovementioned 5 flexion positions, which were different among groups（ F = 3.450 ,P = 0.013 ）.The value was greater at 35° than that at 20° and 25°（ P 〈0.05 ）, and it was also greater at 40° than that at 20° （ P 〈 0.05 ）.Conclusion Cervical flexion angle has an effect on anterior shifting of the posterior wall of the cervical dural canal and widening of epidural space.