INSP-08. Cerebellar mutism syndrome: incidence, symptoms, risk factors, prognosis. Results and future perspectives from the Nordic-European study of the cerebellar mutism syndrome

Cerebellar mutism syndrome (CMS) can be a devastating consequence of paediatric fossa posterior tumour surgery. This prospective observational multi-centre study was designed to investigate incidence, symptoms, risk factors and prognosis of CMS. It has been running since 2014 and is currently involving 28 centres in 10 countries. So far 600 patients have been included as of 1.2.22, and with the aim of including a total of 1000 the study is still ongoing. Analysis of the first 500 patients has described the incidence, course and associated risk factors of postoperative speech impairment (POSI). Midline location, histological diagnosis of medulloblastoma and ATRT and younger age are associated with increased risk of POSI in our cohort. Route of surgical access specifically comparing telovelar to transvermian approach does not seem to influence the risk of POSI. Second surgery is associated with a lower risk of POSI than primary surgery, whereas we found no difference in risk of cranial nerve dysfunction. Left-handedness is not associated with an increased risk of POSI. Further and ongoing analysis include language analyses of recorded patient speech samples, detailed imaging analysis and description of associations between POSI and other neurological symptoms. The results aim to facilitate pre-operative risk assessment and postoperative robust scoring methods for use in clinical trials. Presented on behalf of the CMS study group, clinicaltrials.gov: Nordic study of the cerebellar mutism syndrome.