Morphometric analysis of the posterior fossa volume in patients with Chiari malformations，MRI measurements

English Keywords:Chiari Malformation type I  Posterior fossa volume  Morphometric analysis  Syringomyelia

English Abstract:

  【Abstract】 Objective：To determine the association between the posterior fossa volumes in patients with Chiari malformation type Ⅰ（CMI） and the extent of cerebellar tonsillar displacement as well as syringomyelia.Method：A retrospective radiographic study was performed on patients with CMI，and the inclusion criteria were as followings：（1）age ranging from 16 to 20 years，Risser sign was 5；（2）the diagnosis of CMI in each patient confirmed by a combined head，cervical spine MRI.And age-matched healthy adolescents were recruited as control.On mid-sagittal MRI images，the anteroposterior diameter of the foramen magnum（AB），the length of supraocciput（BC），the anteroposterior diameter of the posterior fossa（CD） and the length of the clivus（AD） were measured to compare the posterior fossa volume between CMI patients and controls.The severity of cerebellar tonsillar descent was classified and the presence of syringomyelia was identified on the sagittal MRI image.Then a further analysis was performed to determine the association between the posterior fossa volume in CMI patients and the severity of cerebellar tonsillar displacement as well as the syringomyelia.Result：37 CMI patients with the mean age of 17.2 year were recruited in this study.Of them，there were 23 males and 14 females.49 normal adolescents with the mean age of 17.5 years were recruited. Of them，there were 24 males and 25 females.Significant differences in all four indexes were found in CMI patients compared with the control group.CMI patients with tonsillar descent of I degree were found to have longer clivus than those with tonsillar descent of Ⅱ or Ⅲ degree.No significant difference of all four indexes was found between CMI patients with or without syringomyelia.Conclusion：The bony components of posterior fossa are malformed in CMI patients，and clivus malformation is critical for cerebellar tonsillar aggravation，while skull malformation may not lead to syringomyelia.