Hi Dave, welcome to CWE!
Firat of all big hugs to you. I imagine it must be a scary time for you right now. It's terrific that you're reaching out for support and information. In my experience, getting informed is one of the best ways of coping with an epilepsy diagnosis (whether it's you OR a family member who's getting diagnosed).
Don't be afraid to ask a lot of questions -- here of course, but more importantly from your son's neurologist. Ideally, he/she should be accessible to answer questions, provide reassurance, go over anything that isn't clear in an open and straightforward manner, etc. In the best scenario, the neuro is an epileptologist (specializing in epilepsy rather than a generalist or specialist in some other neurological disorder). The doctor works for you, not the other way around, and the working relationship should be a collaboration.
That said, I know it’s tough to get a hold of doctors! Your neuro should have explained what they would be looking for with the MRI, but here's my take until you get that info: An MRI is usually standard operating procedure with an epilepsy diagnosis. A focal slow spot on an EEG is typical for epilepsy, and by itself doesn't suggest any particular cause. The MRI can help to identify any structural brain issues (if any) that might be contributing to or directly causing the seizures. Sometimes an MRI can also provide more information about the kind of seizure, which can in turn influence the medication used to treat it. Yes, there are some potentially serious things that an MRI can turn up. No, that doesn't mean your son's doctor thinks that is the case, and in the vast majority of cases the MRI will be negative.
Hope this helps,
Best,
Nakamova