Swelling in the brain after surgery is seen in a fraction of patients. It can be due to multiple causes. What kind of surgery did he have? It's there a CT scan done after the surgery? If yes then please send me the report.
Swelling in the brain is associated with some loss of function in the brain and that may explain some of the symptoms.
Swelling in the brain is mainly controlled by medications. In a few cases, when it does not respond to medications then surgery may be required.