IME, marked personality changes, with no obvious physical cause, are a significant symptom of this disease. If diagnosed, at present treatment is somewhat limited and this can be a difficult disease for the caregiver to cope with.
I know how my mom's personality changed after her stroke, while her brain was healing from the neurosurgery, and I wouldn't wish that on anyone. I thought the insane asylum had descended upon our home.
My sympathies are with you. Definitely verify this diagnosis with a second or third opinion. The expensive scans, MRI, CAT, PET, are usually definitive.
Best wishes!
Pat