My grandmother "had a stroke", but symptoms are really strange. ct scans shows no damage or no stroke. every half hour she repeatedly says the same thing and then stares out in from of her for about 5mins. what could it be?

Stroke: I am sorry your grandmother is having this difficulty and glad you are concerned and trying to help. While CT is often used to asses a brain bleed, it may not show all types of strokes. MRI is better for ischemic stroke, but not always available. Your grandmother’s symptoms sound like seizure activity, but could certainly be due to stroke. Her Neurologist should be able to provide more insight.