gms | German Medical Science

Objective: Pathogenesis and risk factors for cerebellar mutism syndrome (CMS) after posterior fossa tumor surgery are incompletely understood. Disruption of the dentate-rubro-olivary pathway has been suggested, in addition to vermian splitting. We analyzed the temporal evolution of signal abnormalities in this neuronal network in children suffering CMS.

Methods: CMS cases were identified in the institutional database between 2010 and 2017. Demographic variables were recorded and serial MRI scans were analyzed concerning T2 signal abnormality and hypertrophy of inferior olivary nuclei (ION) and dentate nuclei (DN).

Results: CMS occurred in 10 children (15% of the overall cohort), including 6 boys and 4 girls with a mean age of 8 years (range 4–14 years). All microsurgical tumor resections were performed under neuromonitoring using a telovelar approach. Gross or near total resections were achieved in 8 cases. Histology was pilocytic astrocytoma (N=3), anaplastic ependymoma (N=2) and medulloblastoma (N=5). DN injury (N=7) was associated with ION degeneration (N=6), Fisher’s exact test P=0.0333. CMS occurred earlier in children who later developed ION abnormality (P=0.0365). ION hypertrophy and T2 hyperintensity occurred at 5 months after surgery. Hypertrophy resolved at 14 months after surgery, whereas hyperintensity persisted throughout radiological follow-up.

Conclusion: DN injury and ION abnormality are consistent findings in children suffering CMS after telovelar surgery with preservation of the vermis. Those who later developed ION hypertrophy and T2 hyperintensity had in retrospect an earlier onset of CMS after tumor resection. ION abnormalities in this cohort appear to follow a specific time course also reported for other neurological insults to the dentate-rubro-olivary pathway. Preservation of the DN might be at least as relevant as sparing the cerebellar vermis in posterior fossa tumor surgery in children.