Hi My Friend Collapsed At Home. He Was Taken To

Hi my friend collapsed at home. He was taken to emergency. He had difficulty walking one minute and collapsed the next. He was taken to hospital where the doctors diagnosed he had a stroke. His motor area is affected, he has been put on dialysis and is still in a coma. He has been in a coma for 3 weeks. What is his statistical prognosis. I am expecting the best but am prepared for the worst. Is this correct or am I being pessimistic