Hi Emma. MRI is a very sensitive study for picking up AVMs. It would not have missed a clinically significant AVM. This would not explain your symptoms anyway. Your symptoms are very non-specific, meaning they could be caused by any one of a number of things. The findings on MRI may or may not be factors. They are commonly seen on MRI, though usually starting in one's 40's. They are more common in those with certain medical conditions such as high blood pressure, diabetes, high cholesterol, smoking, migraine syndromes and rheumatsim. The fact that you saw a specialist and he was not concerned is very reassuring.
Contrast is helpful for looking for AVMs on CT. It is not necessary with MRI (where it is used more for characterizing tumors). As for AVMs they are hereditary in some families. However, this just means the risk is slightly higher than for an average person. It does not mean that everyone in the family will have one.
Yes. That is the case.