Sagittal taper ratio of cervical spinal canal in adolescents with Chiari malformation and syringomyelia

English Keywords:Chiari malformation  Taper ratio  Anteroposterior diameter  Syringomyelia

English Abstract:

  【Abstract】 Objectives: To assess the sagittal taper ratio of cervical spinal canal in adolescents with Chiari malformation type Ⅰ(CMⅠ) with syringomyelia as comparing to age- and gender-matched controls. Methods: From October 2007 to October 2013, 61 adolescents(28 males and 33 females) with thoracic scoliosis and CMⅠ with syringomyelia, whose average age was 13.7±2.1(10-18) years and average Cobb angle was 51.5°±16.5°(42°-78°) and 75 adolescents(35 males and 40 females) with idiopathic thoracic scoliosis(AIS), whose average age was 14.8±1.8(11-18) years and average Cobb angle was 47.4°±15.3°(40°-69°) in our department were recruited respectively. 60 normal adolescents(28 males and 32 females) were recruited as the control group, whose average age was 15.6±2.6(11-18) years. No significant differences of the age and gender were observed among the three groups(P>0.05). The Cobb angle did not differ significantly between CMⅠ group and AIS group(P>0.05). Anteroposterior diameter of the spinal canal was measured at each cervical level on midsagittal T2-weighted MR images, and a linear trend line was fit by least-square regression to calculate the taper ratio. With the ANOVA test, taper ratios were compared among the three groups and further evaluated with respect to age(≤14 years and >14 years) and gender. Results: Taper ratio averaged (-0.58)±0.42mm/level[(-1.38)-0.98mm/level] in the adolescents with CMⅠ, -(0.28)±0.15mm/level[(-0.02)-(-0.70)mm/level] in the patients with AIS, and (-0.29)±0.28mm/level[(-0.79)-0.33mm/level] in the normal adolescents. Taper ratio of CMⅠ group was significantly steeper than that of the AIS group(P<0.05) and normal group(P<0.05). However, taper ratios did not differ significantly between AIS group and normal group(P>0.05). No significant difference in taper ratio was noted between males and females, or between younger(≤14 years) and older subjects(>14 years)(P>0.05). Conclusions: Adolescents with CMⅠ and syringomyelia have more severely tapered cervical spinal canals than AIS and normal adolescents, suggesting that patients with CMI may have abnormal development of the cervical spinal canal.