Scientists have found evidence connecting head injuries in athletes to Lou Gehrig's disease, according to a report that will air on HBO's "Real Sports" on Tuesday night. Dr. Ann McKee said that she found toxic proteins in the spinal cords of three athletes who had suffered head injuries and then later died of Lou Gehrig's disease, or amyotrophic lateral sclerosis (ALS). Those same proteins have been found in the brains of athletes with chronic traumatic encephalopathy (CTE), a disease linked to head injuries that causes cognitive decline, abnormal behavior and dementia. McKee, a neurology professor at Boston University, noticed that an unusually high number of football players seemed to be affected by ALS.