I was told seizure activity doesn't show (or rarely shows) on an MRI, an MRI/MRA is done to see if something very serious is going on, bleeds etc. they can show scarring/lesions.

Even an EEG (sp) doesn't always show seizures even with people who definitely have them. ( I know, very frustrating)

Don't know what those white spots at the back of your head are, my MRA showed at least 7 lesions/white matter on my frontal lobe and I have seizure like activity too.

Did you get a written report along with the CD yet?