|Classification and external resources|
Boxers receive many blows involving rotational force, which is implicated in concussion. Repeat concussions can lead to dementia pugilistica.
Dementia pugilistica (DP) is a neurodegenerative disease or dementia that may affect amateur or professional boxers as well as athletes in other sports who suffer concussions. A variant of chronic traumatic encephalopathy (CTE) it is also called chronic boxer's encephalopathy, traumatic boxer’s encephalopathy, boxer's dementia, chronic traumatic brain injury associated with boxing (CTBI-B), and punch-drunk syndrome. Symptoms and signs of DP develop progressively over a long latent period sometimes amounting to decades, with the average time of onset being about 12 to 16 years after the start of a career in boxing. The condition is thought to affect around 15% to 20% of professional boxers.
The condition is caused by repeated concussive and sub-concussive blows (blows that are below the threshold of force necessary to cause concussion), or both. Because of the concern that boxing may cause DP, there is a movement among medical professionals to ban the sport. Medical professionals have called for such a ban since as early as the 1950s.
The condition, which occurs in boxers having suffered repeated blows to the head, manifests as dementia, or declining mental ability, problems with memory, and Parkinsonism, or tremors and lack of coordination. It can also cause speech problems and an unsteady gait. Patients with DP may be prone to inappropriate or explosive behavior and may display pathological jealousy or paranoia. Individuals displaying these symptoms also can be characterized as "punchy", another term for a person suffering from DP.
Sufferers may be treated with drugs used for Alzheimer's disease and Parkinsonism.
It is not well understood why this syndrome occurs. Loss of neurons, scarring of brain tissue, collection of proteinaceous, senile plaques, hydrocephalus, attenuation of corpus callosum, diffuse axonal injury, neurofibrillary tangles, and damage to the cerebellum are implicated in the syndrome. The condition may be etiologically related to Alzheimer's disease. Neurofibrillary tangles have been found in the brains of dementia pugilistica patients, but not in the same distribution as is usually found in people with Alzheimer's. One group examined slices of brain from patients having had multiple mild traumatic brain injuries and found changes in the cells' cytoskeletons, which they suggested might be due to damage to cerebral blood vessels.
Increased exposure to concussions and sub-concussive blows is regarded as the most important risk factor, which can depend on the total number of fights, number of knockout losses, the duration of career, fight frequency, age of retirement, and boxing style. One study found that the ApoE4 allele is associated (p < .001) with increased severity of chronic neurologic deficits in high-exposure boxers. Thirty professional boxers underwent neurological assessment and genetic testing for the ApoE4 allele, a known genetic risk factor for dementia, especially late-onset sporadic Alzheimer's disease. The severity of their cognitive, motor, and behavioral impairments was stratified using the Chronic Brain Injury scale, ranging from 0-9 with a score of greater than 0 identified as abnormal. Among 18 boxers with more than 12 professional bouts, those who possessed at least one ApoE4 allele had a higher CBI score (mean 3.9 ± 2.3) compared to boxers without the allele (mean 1.8 ± 1.2). The remaining boxers with less traumatic exposure had a mean score of 0.33, regardless of ApoE genotype.
DP was first described in 1928 by a forensic pathologist, Dr. Harrison Stanford Martland, who was the chief medical examiner of Essex County in Newark, New Jersey in a Journal of the American Medical Association article, in which he noted the tremors, slowed movement, confusion, and speech problems typical of the condition. In 1973, a group led by J. A. Corsellis described the typical neuropathological findings of DP after post-mortem examinations of the brains of 15 former boxers.
Famous cases 
Dementia pugilistica is relatively common among boxers having had long careers and received a great many blows to the head. It is perhaps under-reported because the symptoms often do not become overt until middle age or even later, and are often indistinguishable from Alzheimer's. On the other hand, dementia pugilistica has often been falsely reported. It has been rumored that Jack Dempsey suffered from it, when in fact he retained his mental vigor until his death at 87. Joe Louis developed signs of paranoid schizophrenia that have been attributed to cocaine abuse but may also have a genetic element (his father was institutionalised for mental illness). Other ex-boxers have been said to have had dementia pugilistica when in fact they suffer from nothing worse than a working-class accent and a gruff demeanor (e.g., Rocky Graziano, Tony Zale).
However, Jimmy Ellis, Floyd Patterson (who resigned from the New York State Athletic Commission because of his deteriorating memory), Bobby Chacon, Jerry Quarry, Mike Quarry, Jimmy Young, Wilfred Benitez, Emile Griffith, Willie Pep, Freddie Roach, Sugar Ray Robinson, Billy Conn, Joe Frazier, Fritzie Zivic, and Meldrick Taylor appear to have been genuinely affected by the disorder. Ingemar Johansson may be another victim. In addition, Muhammad Ali's Parkinson's disease was said to be caused by his boxing career, but Ali's own physician Ferdie Pacheco MD states in his Book 'Fight Doctor' that Ali's condition is often misquoted and that Ali, in fact, has Parkinson's Syndrome, which he advises is caused by physical trauma. However, some maintain that this sort of dementia is precisely diagnosed only in autopsy, and claims of retired athletes not having DP are rarely accompanied by autopsy results. On the other hand, diagnosis of Parkinson's disease on the basis of clinical observations is 75-80% accurate.
It can be noted that autopsies of 11 professional American football players by Dr. Ann McKee, of Boston University School of Medicine, found CTE in all cases. CTE has been diagnosed (also by the Boston University group) in one amateur football player, University of Pennsylvania lineman Owen Thomas, following his suicide.
Professional wrestler Chris Benoit was discovered to have suffered from CTE following his 2007 murders and subsequent suicide, as was his former colleague, Andrew Martin, following his 2009 overdose death. Ice Hockey enforcer Derek Boogaard's death in May 2011 has been linked to CTE[how?] which may have developed as a result of bareknuckle fights. News of his ailment has sparked debate about the role of fighting in professional hockey.
See also 
- Concussions in sport
- Traumatic brain injury
- Post-concussion syndrome
- Second-impact syndrome
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