My Son Is 19 Years Old And Has Under Went

My son is 19 years old and has under went 8 surgeries, 4 since Feb 2015 for malfunction of VP shunts. Doctors say the reason he keeps having malfunctions is due to the fact he has Craniosynostis. He has surgery for that scheduled 4/06/16. I'm scared and worried due to the fact that he is much older than those who have this type of surgery. What are the risks? What is the success rate of this type of surgery for someone of his age? We are dealing with a new set of Doctors since his Neurosurgeon (we loved him) decided to go into politics. Please help answer my questions.