This Is MS Multiple Sclerosis Community: Knowledge & Support

Dr. McKee had already found 12 deceased N.F.L. veterans to have had chronic traumatic encephalopathy, a progressive disease in brain tissue that results in cognitive impairment and eventually dementia. Two of those men — Wally Hilgenberg, a longtime linebacker for the Minnesota Vikings in the 1970s, and Eric Scoggins, who played only three games at linebacker for the 1982 San Francisco 49ers — also had A.L.S. diagnosed by their physicians.

When Dr. McKee examined the spinal-cord tissue of those men, as well as a former boxer who had A.L.S.-like symptoms, she found dramatically high levels of tau and TDP-43, two proteins known to cause motor-neuron degeneration. She said that they would appear in the cord as a result of blows to the brain, with the proteins probably traveling down the spinal cord, rather than direct injury to the spinal cord itself.