SHH and medulloblastoma: Evidence has started to emerge on the role of the meningeal immunity in regulation of intrinsic brain tumours, such as medulloblastoma and glioma.73-76 Medulloblastoma is the most common malignant, WHO grade 4, tumour in children and arises in the cerebellum.77 Molecularly, these tumours can be divided into four subgroups: Wingless (WNT, group 1), sonic hedgehog (SHH, group 2), group 3 and group 4.