Traumatic Brain Injury (TBI) that results in disability is seen more often than one would wish. The name Muhammad Ali (born Cassius Marcellus Clay, Jr.; 1942) comes to mind. Some consider among the greatest American heavyweights in the history of boxing. By the 1980's, Ali was already beginning to exhibit symptoms that included vocal stutters and trembling hands and by 1984 it was reported that he was suffering from pugilistic Parkinson's disease, common to head trauma from activities such as boxing. Eventually he would lose the ability to speak. The TBI can result in a neurodegenerative disease with features of dementia. It may affect amateur or professional boxers, wrestlers, and athletes in other sports who suffer concussions. Repetitive concussions are common as well to quarterbacks, wide receivers, hockey and soccer forwards, and especially the goalies. Occasionally, even a baseball catcher defending home plate will experience a concussion. The so-called glory and excitement of such sports can exact a horrible price from the players. What happens in the brain that results in these symptoms of disability? More on that tomorrow.