A space-occupying lesion occupying the infratentorial compartment would have the greatest effect on:

The tentorium cerebelli separates the superior surface of the cerebellum from the occipital and temporal lobes, defining supratentorial and infratentorial compartments within the cranial vault. The supratentorial compartment contains the forebrain, and the infratentorial compartment (or posterior fossa ) contains the brainstem and cerebellum.