Please note this:
"If the level of phenytoin in your blood gets too high, it can cause symptoms such as confusion, rapid involuntary eye movements, blurred vision, slurred speech or clumsy movements. You should tell your doctor if you experience any of these symptoms while taking phenytoin, so that your blood level of phenytoin can be measured and your dose reduced if necessary. "
Also, he has had a major surgery, and will need time to recover. However, any changes need to be reported to the doctor.
I hit my head on a trampoline when I was thirteen. I was told I had torn the skin surrounding the brain. The pain never truly goes away, but surprisingly coffee helps.