Correlation between posterior fossa volume and the severity of cerebellar tonsillar descent/MR imaging of syringomyeliain patients with Chiari malformation

English Keywords:Chiari Malformation  Posterior fossa volume  Cerebellar tonsillar descent  Magnetic resonance imaging  Syringomyelia  Morphometric analysis

English Abstract:

  【Abstract】 Objectives: To compare the posterior fossa volume among patients and magnetic resonance imaging of syringomyelia with various degrees of cerebellar tonsillar descent, and to explore the potential anatomical factors of cerebellar tonsillar descent. Methods: A total of 59 patients with Chiari malformation type Ⅰ(CMⅠ) treated in our center from June 2003 to June 2011 was recruited. On mid-sagittal magnetic resonance images, the degree of tonsillar descent, configuration of syrinx, clivus length, anteroposterior diameter of the foramen magnum, supraocciput length, anteroposterior diameter of the posterior fossa, osteal posterior fossa height and clivus gradient were measured. Morphometric analysis was conducted among patients with different degrees of cerebellar tonsillar descent and with various patterns of syrinx configuration, respectively. Results: There were no significant differences in the results of anteroposterior diameter of the foramen magnum, supraocciput length, anteroposterior diameter of the posterior fossa and osteal posterior fossa height among patients with various degrees of tonsillar descent(P>0.05) and with various patterns of syrinx configuration(P>0.05). The clivus length in patients with grade Ⅰ tonsillar discent was significantly longer than that in patients with grade Ⅱ or Ⅲ tonsillar descent(P＜0.05). The clivus gradient in patients with grade　Ⅲ tonsillar discent was significantly smaller than that in patients with grade Ⅰ or Ⅱ tonsillar descent(P＜0.05). The analytic results showed that the result of clivus gradient had remarkable negative correlation with the degree of tonsillar descent(r=-0.626, P=0.005). Patients with distending syrinx had a larger clivus gradient in comparison with those with other types of syrinx(P＜0.05). Conclusions: A shorter and flatter clivus can increase the risk of aggravation of tonsillar descent and has an effect on the progression of syrinx.