The effect of posterior fossa decompression in adult Chiari malformation and basilar invagination: a systematic review and meta-analysis.

Chiari malformation (CM) and basilar invagination (BI) are mesodermal malformations with disproportion between the content and volume of posterior fossa capacity and overcrowding of neural structures at the level of foramen magnum. Several alternatives for posterior approaches are available, including extradural (ED), extra-arachnoidal, and intradural (ID) approaches. The objectives are to evaluate the effect of several surgical techniques for posterior fossa decompression (PFD) in the outcomes of patients with CCJM and to evaluate complications in the techniques reported. A systematic review of the literature on the effects of PFD surgery was performed using the MEDLINE (via PubMed) database and the Cochrane Central Register of Controlled Trials. The PRISMA statement and MOOSE recommendations were followed. Five hundred and thirty-nine (539) articles were initially selected by publication title. After abstract analysis, 70 articles were selected for full-text analysis, and 43 were excluded. Ultimately, 27 studies were evaluated. The success rate (SR) with ED techniques was 0.76 versus 0.81 in EA technique and 0.83 in IA technique. All posterior fossa decompression techniques were very successful. Results from observational studies were similar to that of the randomized trial. The main complications were CSF fistulas, most common in patients with IA approach. The overall mortality rate was 1%.