In October, 1991, a 17 year-old high school football player was tackled on the last play of the first half of a varsity game and struck his head on the ground. During halftime intermission, he told a teammate that he felt ill and had a headache; he did not tell the coach. He played again during the third quarter and received several routine blows to his helmet during blocks and tackles. He then collapsed on the field and was taken to a local hospital in a coma. A computed tomography (CT) brain scan revealed diffuse swelling of the brain and a small subdural hematoma. …