I've been out of town, for work, and am not following everything going on, so forgive me if this was already explained what testing you had done.
While fostering my Bianca, she was acting odd. I immediately called another Rescue, and was told it sounded like a stroke. I called my vet, first thing in the morning, and said, "Bianca had a stroke". I was panicked. I hadn't slept all night. I'll have to find the thread, but in the mean time she had a few seizures, which was why she was acting odd. I had not witnessed her original seizure, and it didn't occure to me. But it had nothing to do with a stroke. My vet questioned "why" I mentioned stroke. Bianca was put on Phenobarbital, and was fine after that. She did pass, within a few months, but it had nothing to do with a stroke.
I'm always learning, and need to learn. How do you know she had a stroke?