A 5-year-old boy undergoes whole-body MRI during investigation for chronic recurrent multifocal osteomyelitis (CRMO). An incidental posterior fossa abnormality is identified.
Upon further questioning, they have been complaining of headache for the previous month. Dedicated imaging of this area shows a 2.6 cm lesion arising from the cerebellar vermis and extending down from the roof of the 4th ventricle. This area is low signal on T1 imaging, heterogeneous but isointense to normal brain on T2 imaging and restricts diffusion on diffusion weighted imaging. The patient has no hydrocephalus. What is the most appropriate definitive treatment?