Study – Why are CTE Symptoms Worse for Boxers vs. Other Athletes?

An interesting study was published recently in the Journal of Vascular and Interventional Neurology reviewing published literature involving CTE in athletes looking for an explanation for the variation in clinical presentation between athletes of different sports.

The full study,  titled Chronic Traumatic Encephalopathy in Athletes Involved with Highimpact Sports, can be found here.

Two combat sports worthy topics were addressed.  First the authors discussed the worse symptoms of CTE in boxers vs other athletes such as football players.  The authors hypothesize that the clinical presentation in boxers may be more profound due to the rotational forces associated with hook punches as opposed to the linear forces from straight on collisions.  Second the authors repeat the advice that a strong neck is a useful asset in reducing risk for head trauma for athletes.

The authors note as follows:

Clinical and pathological features of CTE can manifest differently between sports, as rTBI exposure and mechanisms of impact can vary considerably. In fact, an analysis of previously reported CTE cases by Montenigro et al. [29] showed a vast difference in clinical presentation. 83% (5/6) of professional boxers, who had more debilitating motor impairments, compared to 18.8% (3/16) of professional football players. In addition, severe dentate neurofibrillary tangles were present in 17% (2/12) and 80% (4/5) of professional football players and boxers, respectively, indicating a more pernicious progression in boxers [29]. The difference in symptoms and neuropathology may be explained through the frequency of linear and rotational impact forces that occur in both sports.

Rotational forces causing angular accelerations are frequent in boxing. Boxers face their greatest danger when their opponent lands a hook punch, where impact near the lateral side of the head cause rapid outward rotation of the skull and twisting forces the brain [29]. Lateral bending of the neck can also occur, but linear forces from a punch are often below the mTBI threshold [58]. The rotational movement of the brain causes shearing forces that can lead to axonal damage [59]. Shearing forces are most prominent near areas such as the midbrain section, where glial and axonal injury could result in severely debilitating consequences [29,58].

As opposed to punches, helmet-to-helmet or helmet-toground contact forces cause the majority of mTBI injuries in professional football players. Viano et al. [58] have shown that in professional football concussions, inertial forces can be up to 30% greater than inertial forces in professional boxers who endure a hook punch. The greater inertial forces correlate with a higher linear acceleration endured by football players, suggesting that linear forces are prominent in causing concussive and subconcussive impacts in professional football players. In support of this mechanism, brain modeling shows that rotational accelerations from uppercuts or hook punches are much greater than rotational accelerations in professional football helmet-to-helmet impacts [58]. The linear to rotational force ratio difference between boxers and football players could explain the differences in clinical presentation between the two sports.

In professional football, helmet-to-helmet collisions can cause the head to move in the anterior or posterior direction. The incidence rates of mTBI have been shown to vary depending on position, with running backs and wide receivers suffering from mTBI more than linemen [60]. Neck musculature acts to stabilize the position of the head, and a more developed musculature is directly correlated to lowered mTBI risk [61]. Linemen have been found to have stronger necks and larger girth compared to running backs, which could act to slow linear accelerations of the head and reduce risk of mTBI [62]. The differences in neck strength between positions may explain the varying incidence rates of mTBI. Additionally, it should be noted that different player positions may be more prone to certain types of impacts—linemen may experience more frequent subconcussive helmet-tohelmet impact, while wide receivers could endure more threatening forces while being tackled. The pathological repercussions of variations in impact type and frequency between boxing and football have yet to be elucidated in full detail, but they may partially explain the difference in clinical presentation between different types of athletes.

One thought on “Study – Why are CTE Symptoms Worse for Boxers vs. Other Athletes?

  1. Interesting article.

    Boxers were the original ‘canaries in the coalmine’ of CTE. Back in the ’20s it was called Dementia Pugilistica because it was thought to be unique to boxers. I imagine the multiple blows to the head–often extremely hard & direct–are what makes boxing CTE more severe. The entire goal is to knock your opponent out. In football it’s just a “bonus” if your opponent loses consciousness.

    Football players don’t always take direct head hits, but when they do they can be devastating. I watched some clips of ex-boxers with CTE & their symptoms are indeed more noticeable than ex-NFL players: slurred speech (sometimes severe), shuffling gait, blindness & deafness, Parkinsonian tremors & forgetfulness seem to affect boxers and MMA fighters more severely and earlier than footballers with the disease. In footballers, it often comes across as aggression & rage (Aaron Hernandez, Jovan Belcher, Ray Rice), while with boxers it seems to be more like early-onset dementia (Jerry Quarry, Ali, Gary Goodridge). Of course there are exceptions. I’d bet my life that O.J. Simpson and Mike Tyson have it to some degree.

    But now that we know the symptoms & risk factors, I’m sure we’ll be spotting a lot more cases that would’ve flown under the radar 20 years ago. The ethical question is, what can realistically be done to prevent it? We live in a sports-obsessed nation. What’s scary is the number of kids & teens silently incurring lifelong damage from sports, domestic abuse & other preventable causes. These injuries could have a very high societal cost rivaling that of smoking or obesity. Disability, violent crime, car accidents & other such things could result from early brain damage. I’d’ be willing to bet the rate of previous TBI & concussion is pretty damn high in our prisons.

    I have a feeling that there is no “safe level” of brain trauma and that ANY hit to the head could cause lasting symptoms in some people, even if it’s subconcussive and only happens once or twice. Perhaps folks with a history of mental illness or drug abuse might be more affected–we just don’t know. I look forward to learning more & watching science & history unfold on this.

Leave a Reply

Fill in your details below or click an icon to log in: Logo

You are commenting using your account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s