Thank you for posting your query at DoctorSpring.com
I have noted your wife's symptoms. The most likely cause for her symptoms would be migraine with visual aura. Since she has frequent episodes, she should be started on preventive medications to reduce the chances of a similar episode occurring in the future.
In addition, in view of her other neurological symptoms such as decreased vision, speech problems, etc, we need to exclude other conditions also. The most important one are collagen vascular disease and vasculitis. These are inflammatory conditions, which cause narrowing of blood vessels in the brain.
I would recommend doing an angiogram (CT angiogram or DSA) to exclude vasculitis.
I hope it helps.
Dr. Sudhir Kumar MD (Medicine), DM (Neurology)
Senior Consultant Neurologist