The term "chronic encephalopathy" or "chronic brain injury" of boxers encompasses a wide spectrum of disorders. At one end are boxers with minimal involvement and at the other end are severely affected boxers requiring institutional care. Along the spectrum are some boxers with varying degrees of speech difficulty, stiffness, unsteadiness, memory loss, and inappropriate behavior. The more severely affected boxers gave rise to labels such as "punch drunk".
In different studies, 15-40% of ex-boxers have been found to have symptoms of chronic brain injury. Most of the boxers have mild symptoms. Recent work, employing detailed psychological testing and MRI scanning, has shown that most professional boxers (even those without symptoms) have some degree of brain damage. Although obviously symptomatic cases still occur, they are less common today probably because today's boxers have fewer bouts and shorter careers, resulting in fewer blows to the head and less cumulative brain injury.
Onset of Symptoms
Symptoms usually begin near or shortly after the end of a boxer's career. On occasion they are first noticed after a particularly hard bout. Symptoms develop an average of 16 years after beginning the sport, although some cases have occurred as early as 6 years after becoming a boxer. Symptoms have been reported in boxers as young as 25 years of age. Although the disorder has been reported in amateurs, it is more common in professionals. It can occur in all weight classes but is seen most often in the heavier divisions, and champion boxers run as much risk of sustaining chronic brain injury as less skilled journeymen.
Recent work has demonstrated that MRI abnormalities and minimal memory deficits occur in many boxers who appear normal. These minimal deficits can begin after only a few years in the sport. While boxers with less than 20-30 professional bouts usually do not have any symptoms of brain injury those with 25-50 bouts often show MRI and psychological test abnormalities without obvious symptoms. Boxers with more than 50 professional bouts often have obvious symptoms of brain injury as well as MRI and psychological test abnormalities.
This continuum of symptoms strongly suggests that the chronic encephalopathy of boxers is a progressive illness. The older literature contains numerous case reports that document a progressive deterioration, even after the boxer had retired from the ring. The Parkinson-like disorder is as progressive as the other forms.
As the damage accumulates, minimal symptoms merge gradually into more obvious symptoms. The boxer usually is not aware of his difficulties; his wife is often the first to notice subtle personality changes. Extreme intolerance of alcoholic beverages is a common symptom in the early stages. Confrontations with law enforcement authorities are often the result of lost social inhibitions or sudden changes in mood and behavior. These difficulties usually are explained away as symptoms of depression, anxiety, or even the enthusiasm of an immature aging athlete. An example of such behavior is the ex-heavyweight champion Mike Tyson.
Early motor symptoms usually are noticed first by the trainer. A mild lack of coordination, subtle loss of balance, or a generalized "slowing down" initially are attributed to the natural aging process. However, as these symptoms worsen, it may become apparent to the boxer's companions that something is wrong, even while the boxer continues to insist that he is perfectly healthy.
