What Is The Prognosis Of Coma?

Hello. I have a question about a brain aneurysm. He is 59 years old and had a very bad headache and high blood pressure, the next morning he was unresponsive and rushed to the hospital. The ct revealed blood in all four ventricles. He has been in a coma for a week in a half now, not improving or getting worse either. He is still not repsonding at all. What do you think are the chances of his survival?