I have an AVM of similar size in my temporal lobe. I had a bleeding back in 2011 when I was 22 years old, and I had episodes of migraine before that.
I have doctors (one of which was Dr. Duke Samson who was renowned in this area) who recommended to not operate on it even though it had bled before, because the AVM location is deep and the risk of a major hemorrhage is relatively small because it’s a “high flow low pressure” AVM.
But after another episode of bleeding in 2015 another team of doctors recommended to treat it. I had two embolization procedures and a proton therapy by Dr. Patel and Dr. Chapman in MGH since then. I’m still waiting on the effect proton therapy to fully develop. In the meanwhile I did have another bleeding in 2019. Thankfully I have fully recovered in all three instances.
All the doctors I’ve seen always tell me I don’t need to rush to decide on my treatments. I had plenty of time to research on my treatment options. Sounds like your son hasn’t have an AVM rupture, so his risk is even lower. Also my first doctor cited a clinical trial (ARUBA) that concluded unruptured AVMs should not be operated surgically. I hope that’ll make you feel better