ADHD can't be tested with EEG or MRI. I mean, with EEG, you can *technically* monitor brain wave activity and make a guess as to whether someone has ADHD, but it's not a good diagnostic tool for ADHD at all and you shouldn't ever do that. Plus, it's cheaper and easier to just give someone a written/oral test to assess whether someone has ADHD or not... and even then, those tests aren't perfect.

In general, EEGs and MRIs are used to rule out various neurological conditions that cause ADHD-like symptoms. Here's a list of 50 conditions whose symptoms mimic ADHD symptoms: 50 Conditions that Mimic ADHD | AbleChild.org

I'm guessing one or more of your doctors suspect a neurological problem based on what you told them. Your signature does say "possible Adrenal Hyperplasia".

Anyway, whatever the outcome, I'm sure it will help you better understand what you're going through. Best of luck