Analysis of presurgical language in children with posterior fossa tumours relative to postoperative speech outcomes: findings from the European CMS study

Background. Cerebellar Mutism Syndrome (CMS) is a common complication in children following posterior fossa tumour (PFT) surgery, typically marked by transient postoperative speech impairment (POSI; i.e., mutism or reduced speech). Differences in language performance between children with and without POSI have been observed postoperatively, but it remains unclear to what extent these language difficulties exist preoperatively and whether preoperative difficulties are related to POSI. This study provides the first comprehensive analysis of preoperative language samples, using data from the European CMS study. The aim was to compare patients who did or did not develop POSI to identify preoperative language characteristics that may be associated with POSI. Method. Preoperative language samples of 34 patients aged 3–17 years were analysed, including 16 who later developed POSI and 18 who did not. An analysis was performed to compare sample characteristics and language performance across four levels: semantics, lexical, morphosyntax, and phonology. Results. No significant preoperative language differences were found between the groups for the levels of language processing (all p -values > .137). Children who developed POSI produced more unintelligible speech preoperatively (β = -14.455, p = .024), but their intelligibility improved with age (age×group: β = 0.152, p = .007), whereas intelligibility in children without POSI remained relatively stable across age. Conclusion. These findings suggest that risk factors for POSI within the domain of verbal output may lie more in preoperative speech than in language. A comprehensive analysis of preoperative speech may provide valuable insight into speech characteristics potentially related to POSI.