AV Malformation with kids

[jay_hoo]

i was 6 years old when i had my first AVM which resulted in me having brain surgery. 8 months or so after having this surgery i had another to remove a sist that formed over top of the surgical sit. my question is how does a AVM start? what causes them to be created?  do to i was so young i did not get the chance to ask any questions about what was happening. i hope some one out there can help me out.

thanks