What Causes Slurring Of Speech And Fever After A Head To Head Fight?

My 21 year old cousin (male) who is an athlete was wrestling 13 days ago when he collided with another person head to head. He saw stars and it was a hard hit. I am not sure if he was knocked out at all, but he returned to the mat. He went home with a headache and practiced again the next day. He went home where he started running fever of 103 and was very sick for the next two days. He went to the ER where they did did cat scan, spinal tap, and blood work which all came back clear. They admited him to try and get his fever down. The fever got down by meds and they released him, but for the next two days he bagan to fall down, not make sence with words and was very slow with his thought process as well as his eyes were kind of wild. He still had fever that spiked when meds wore off and was taken again to a different hospital where he was admited again last night. He was barely talking and made no sence at all. He was seeing thibngs and talking out of his head. He is now in ICU staring at the wall and has not said a word to anyone. This seems to be progressing very fast can someone please help?