Preoperative language in children with posterior fossa tumours relative to typically developing peers: findings from the European CMS study

Background. Language impairments after surgery and adjuvant treatment are common for paediatric patients with posterior fossa tumours (PFTs), but it remains unclear to what extent they are already present before treatment. We investigated preoperative language production in patients with PFTs to characterise tumour-associated language difficulties and their linguistic nature. Method. Narrative language samples from 56 children with PFTs and 56 age-, sex-, and language-matched typically developing controls were analysed. Twenty-four measures at the semantic, lexical, morphosyntactic, and phonological levels of language processing were clustered using principal component analyses and compared between children with PFTs and healthy controls, using linear models adjusted for age and language. Results. Before treatment, children with PFTs produced shorter narratives and received more prompting from the examiner than controls. They also showed poorer morphosyntactic performance characterised by reduced grammatical accuracy and finiteness, and showed poorer phonological performance characterised by more phonemic errors and incorrect consonant clusters. Exploratory analyses showed no effects of hydrocephalus and limited effects of tumour type, whereas children with hemispheric tumours performed worse than those with vermal tumours on several measures. Conclusion. Children with PFTs already show morphosyntactic and phonological differences before neurosurgical treatment, indicating that language difficulties in this population cannot solely be attributed to surgery or adjuvant therapy. These findings are consistent with a functional involvement of the cerebellum and its connections to language processing and underscore the importance of preoperative language assessment.