Heralding cerebellar mutism: evidence for pre-surgical language impairment as primary risk factor in posterior fossa surgery.

The aim of this study is to identify possible risks factors for the occurrence of cerebellar mutism syndrome (CMS) in children with posterior cranial fossa tumours. Children diagnosed with posterior fossa tumours consecutively admitted to our institution between 2006 and 2008 were the subjects of this prospective study. Besides standard neurological and radiological evaluations, all children underwent thorough neuropsychological assessments at admission and following surgery. Children under two or older than 16 years of age and those with a severe pre-operative clinical condition precluding neuropsychological assessment were excluded. Thirty-four children met the inclusion criteria. They were divided into two groups. Group I consisted of 23 children with normal language on admission and group II had 11 children showing pre-operative language impairment (PLI). PLI was observed in 11 children (32.4%: group II). Post-operatively, seven out of 34 children developed CMS (20.6%), all of them belonging to group II. In group II, indeed, the incidence of CMS was 63%. No case of CMS was observed in group I. PLI regressed after the operation in three out of the four subjects belonging to group II who did not develop CMS. PLI remained unchanged in the last child of this group. Posterior fossa tumour resection can have different effects on children with pre-existing language impairment (PLI). PLI can be considered a subclinical state of CMS in some children with posterior fossa tumour. However, in some children with PLI, the tumour resection may improve the linguistic abilities, as well as the other neurocognitive performances. In the present series, children with normal pre-operative language function did not develop post-operative mutism.