What Causes Blocks In The Brain?

My father underwent a brain surgery for hemangeopericytoma in the left occipital 11 days back and his responses were not good after the surgery. doctors took a CT scan and confirmed that there was no blood leakage or anything like that and we have to wait till dad responds back. after 1 week there was slight improvement in dad's response but suddenly it came completely down. one more CT scan was down which showed air blocks in many places in the brain. why there are so many air blocks and how it could be removed and what are the consequences?