Impact of molecular subtypes on postoperative hydrocephalus following resection of posterior fossa medulloblastoma and ependymoma in children: A systematic review and meta-analysis

Objective: The objective of this systematic review was to investigate the possible impact of tumor molecular subtype on the risk of postoperative hydrocephalus following resection of posterior fossa ependymomas and medulloblastomas in children. Methods: A Preferred Reporting Items for Systematic Reviews and Meta-Analyses guideline based systematic literature review and meta-analysis was performed using the PubMed and Embase databases. The final searches were conducted on February 1st, 2025. Predetermined eligibility criteria were based on the Population, Intervention, Comparison and Study design framework. A risk of bias analysis was performed using the Risk of Bias In Non-randomized Studies of Exposures tool. Count data was pooled across the included studies with the addition of a 10-year nationwide cohort from Denmark (DK cohort). Extracted data from medulloblastoma studies were compared using chi-squared tests and calculations of relative risks. Results: A total of four studies were included, three of which pertained to medulloblastoma (MB). In total, postoperative hydrocephalus was reported in 22.4% (68/304) of children with MB. The lowest rate was observed for MB_WNT (7.9%), and the highest for MB_Grp3 (29.7%), however the difference across molecular subtypes was not statistically significant (p = 0.08, chi-squared). The relative risk of postoperative hydrocephalus was significantly lower for MB_WNT when compared to non-MB_WNT (RR of 0.32 [95% CI, 0.11–0.98]), and significantly higher for MB_Grp3 when directly compared to MB_WNT (RR of 3.76 [95% CI, 1.19–11.87]). Only one of the four included studies pertained to children with posterior fossa ependymomas (EPN). For EPN, postoperative hydrocephalus was reported in 26.5% (22/83) after pooling with the DK cohort data (n = 14), with similar rates for Posterior Fossa Type A (PFA-EPN) (27.0%) and Posterior Fossa Type B (PFB-EPN) (22.2%). Conclusions: In this systematic literature review, we investigated the potential association between tumor molecular subtype in children with posterior fossa EPN and MB and postoperative hydrocephalus. Here, we show that the rate of postoperative hydrocephalus is significantly lower for MB_WNT when compared to non-MB_WNT and significantly higher for MB_Grp3 when compared to MB_WNT selectively. No clear difference was observed across PFA-EPN and PFB-EPN, possibly due to the limited number of patients. Improving our understanding of cerebrospinal fluid disturbances associated with posterior fossa tumors holds potential to further optimize the treatment of hydrocephalus in these children in the future.