Prognostic analysis of posterior fossa decompression with or without cerebellar tonsillectomy for Chiari malformation type I: a multicenter retrospective study

OBJECTIVE The purpose of this study was to compare the prognosis of patients with Chiari malformation type I (CM-I) treated with posterior fossa decompression with duraplasty (PFDD) and posterior fossa decompression with resection of tonsils (PFDRT). METHODS The clinical data of patients with CM-I treated using these two procedures in three medical centers between January 2016 and June 2021 were retrospectively analyzed and divided into PFDD and PFDRT groups according to the procedures. The Chicago Chiari Outcome Scale (CCOS) was used to score the patients and compare the prognosis of the two groups. RESULTS A total of 125 patients with CM-I were included, of whom 90 (72.0%) were in the PFDD group, and 35 (28.0%) were in the PFDRT group. There was no significant difference in the overall essential characteristics of the two groups. Moreover, there was no significant difference in complication rates (3.3% vs 8.6%, p = 0.348), CCOS scores (13.5 +/- 1.59 vs 14.0 +/- 1.21, p = 0.111), and the probability of poor prognosis (25.6% vs 11.4%, p = 0.096) between the two groups. Nevertheless, a subgroup of patients who had CM-I combined with syringomyelia (SM) revealed higher CCOS scores (13.91 +/- 1.12 vs 12.70 +/- 1.64, p = 0.002) and a lower probability of poor prognosis (13.0% vs 40.4%, p = 0.028) in the PFDRT than in the PFDD group. Also, SM relief was more significant in patients in the PFDRT compared to the PFDD group. A logistic multifactor regression analysis of poor prognosis in patients with CM-I and SM showed that the PFDRT surgical approach was a protective factor compared to PFDD. Furthermore, by CCOS analysis, it was found that the main advantage of PFDRT in treating patients with CM-I and SM was to improve patients' nonpain and functionality scores. CONCLUSIONS Compared with PFDD, PFDRT is associated with a better prognosis for patients with CM-I and SM and is a protective factor for poor prognosis. Therefore, the authors suggest that PFDRT may be considered for patients with CM-I and SM.