following surgery may be due to a variety of causes. Since the CT scan
is normal so causes that would be most likely are imbalance of electrolytes (like sodium etc) in the blood. But since both neurosurgeon and neurologist
have seen, I am sure this must have been tested and ruled out by them. He is very old and with aging body is not capable of handling problems as well as a young body is. I will agree with your doctors that waiting hoping for the best is the only option. If it is feasible in your hospital, MRI
may be helpful in coming to a conclusion.