Posterior Fossa Dimensions of Chiari Malformation Patients Compared with Normal Subjects: Systematic Review and Meta-Analysis.

Abstract

Chiari malformation (CM) is defined as a herniation of cerebellar tonsils below the foramen magnum and is considered to be due to underdevelopment of posterior fossa (PF) bone components. There is overcrowding of neural structures, and normal cerebrospinal fluid circulation is frequently blocked. Although several publications exist of measurements of dimensions and volumes from bone components of PF in CM, there is no systematic review evaluating quantitatively these dimensions. The aim of this study was to evaluate PF dimensions and volumes in a meta-analysis. An electronic search using PubMed and Google Scholar was done. Study eligibility criteria were defined by the PICO strategy, which selected patients and interventions. Studies comparing PF dimensions between patients with CM and normal subjects were selected. A meta-analysis of pooled data was done using statistical software. Data for pooled analysis were obtained from 12 studies. Data synthesis was based on small published sample sizes in the majority of studies. Key findings included smaller measurements of clivus, supraoccipital bone, and PF area dimensions in patients with CM compared with normal subjects. Brainstem and cerebellar length was not different between groups. This review provides evidence of smaller measurements of clivus, supraoccipital bone, and PF area dimensions in patients with CM compared with normal subjects. An implication of the key findings is that surgical treatment of CMs should consider the smaller dimensions of PF in planning.