Shadow on ct scan mastoid bone area, mri results clear, had ear infection and still do. would mri only show intercrainial and not bone disease?

CT or MRI?: Ct is the superior study to define issues within the ear and temporal bone. Mri is the superior study to define issues involving soft tissue such as brain.

Probably: Mri and ct are complementary studies so there is always the possibility that one study will show an abnormality that the other doesn't. Typically a 'shadow' in the mastoid bone means fluid and that should show up on mri. But not knowing for sure what is meant by 'shadow' in your case, i can't be 100% about that. Ask your doctor about your case specifically or an ENT specialist or a neurologist.