The 9-year-old Fairland, Ind., boy was struck in the head on July 4 while playing the children's game.
When he began to vomit and have severe headaches days later, his parents took him to a hospital where doctors made an alarming discovery, reports WRTV-TV in Indianapolis.
While there was no trauma from being hit, tests revealed a golf ball-sized mass in Jacob's brain.
Doctors were able to remove most of the mass but a small piece remains, wrapped around a nerve, the television station reports.
"(I had surgery) in my brain, so I can be better," Jacob told the station.
Doctors suspect the mass is benign, but Jacob will likely undergo chemotherapy to prevent the remaining piece from causing problems.
"The doctors told us that this is something that he's probably had for a while. Had he not got hit with that kickball, who knows what would have happened," Andy Hamilton, Jacob's father, said.
- Disease & Medical Conditions