problems 2 1/2 months after serious brain injury

My nephew suffered a severe head trauma over two months ago.  They did a large % cranioplasty procedure which they just put back on two weeks ago.  There was a definite change following the procedure of flatness in demeanor and initiation of response.  Three days ago he developed tremors and great head pain.  He also has some hydrocephalus, but mild, and a subdural hygroma (which they just attempted to drain tonight by drilling through his acrylic skull piece, It was a slow two week progression downhill that led up to the tremors (major) and head pain that accompanies them.  The doctors are really not sure how this is all connected.  He has had EEGs that show the tremor/seizure activity does not seem to be cortical.  CT scans and MRIs have show where the fluid is located.  A spinal tap has indicated no excessive pressure in CS fluid and no infection.  The scans do show ventricular enlargement.  Any ideas are appreciated and timely......it is happening now and they are stumped.