Preoperative hydrocephalus and the risk of postoperative speech impairment following posterior fossa tumour surgery in children: results from a prospective, multinational cohort study

Background: Cerebellar mutism syndrome (CMS) is a common complication of paediatric posterior fossa (PF) tumour surgery, with postoperative speech impairment (POSI) as the cardinal symptom. Preoperative hydrocephalus (pHC) is present in up to 70% of cases of paediatric PF tumours, but its association with POSI remains unclear. This study investigated whether pHC is an independent risk factor for POSI and assessed the impact of alleviating pHC prior to tumour resection on POSI risk. Methods: We included 800 children who underwent PF tumour surgery between 2014 and 2024 at 35 centres across 13 countries in the European CMS study. Speech and neurological assessments were conducted pre- and postoperatively. Neurosurgeons assessed pHC status, pHC treatment and tumour location; histology was recorded at a 2-month follow-up. pHC treatment was categorised as “yes” (pHC alleviated prior to tumour surgery) and “no” (pHC alleviated by tumour surgery alone). POSI was categorised as “habitual speech”, “reduced speech” or “mutism”. Results: Of 800 patients, 515 (64%) had pHC. Absence of pHC was associated with lower POSI risk in univariate analysis (OR 0.51 (95% CI 0.35; 0.76)), but this reversed and became non-significant after adjustment (1.20 (0.60; 2.41)). pHC treatment was associated with an increased POSI risk in the univariate analysis (1.93 (1.14; 3.26)), which became non-significant in the adjusted analysis (1.15 (0.60; 2.21)). Conclusion: The presence of pHC was not independently associated with POSI nor did treatment of pHC prior to tumour resection appear to reduce the risk of POSI. These findings highlight the importance of individualizing pHC management in paediatric PF tumour cases, with decisions guided by the clinical context. Trial registration: Clinical Trials ID NCT02300766 (October 2014).