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Conor McGregor Wasn't Fatigued; He Was at Risk of Brain Damage

Dizziness and loss of balance is one of the hallmarks of mild traumatic brain injury.
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This past weekend was host to what some billed as the biggest fight in combat sports history: the notorious Conor McGregor was defeated by Floyd Money Mayweather via TKO in the 10th round of a traditional boxing match. Most boxing pundits gave McGregor little to no chance, but the consensus is that McGregor, in his first-ever professional boxing match, performed better than expected. Mayweather admittedly started slowly on purpose, and by the 9th round he began inflicting heavy damage by landing several power shots to the head. In the 10th round McGregor became what he described as "wobbly and floaty," forcing Hall-of-Fame referee Robert Byrd to call a stoppage to the fight.


McGregor attributed his wobbly movements to fatigue, something he has experienced in prior fights. "I would have liked to see the end of the 10th… I have this patch where I must overcome, I get a little wobbly, but it's more fatigue. If you look at the Diaz 2 fight, I came through that," he said in a post-fight press conference.

But Byrd's calculation to call a stoppage was likely not based on signs of fatigue, but rather signs of traumatic brain injury. Ataxia, or dizziness and loss of balance, is one of the hallmarks of concussion, a type of mild traumatic brain injury. Fatigue may cause sluggish and slow movements, but does not cause the imbalance and poor coordination exhibited by McGregor in the 10th round. Being wobbly, in the setting of pugilistic trauma, will always be treated as the result of head trauma and not as fatigue. To let a fighter continue on would be grossly negligent.

The organ the ringside physician is concerned about when a fighter displays ataxia is the brain, and the specific part is a small area near the back of the skull called the cerebellum. The cerebellum functions to coordinate and regulate movements, and when it's injured, will result in lack of precision and accurate timing of body movements. It is typically tested by the finger to nose test, during which any abnormalities will be noticeably amplified by an outstretched finger. The cerebellum frequently exhibits malfunction during concussion and traumatic brain injury due to its location at the back of the skull, predisposing it to something called a contrecoup injury. This occurs when a force is applied to the front of the skull, such as a Mayweather punch, causing the brain to accelerate backwards and hit the back of the skull. Global brain rotational forces and acceleration/deceleration will also contribute to cerebellar injury.

McGregor maintained, "it's not damage, there's always a patch in my fights where I go through this fatigue stage… but I wasn't rocked." As an Irishman and self-admitted McGregor fan, I would like to believe him, but as a physician and former ringside doctor, I believe the fight was stopped for his own safety. Byrd did an excellent job by stopping the fight when he did, as I'm certain the ringside physician and all members of the Association of Ringside Physicians would agree.

It was an entertaining contest, and while he is likely devastated by the loss, McGregor should be quite pleased by his performance against arguably the best boxer who has ever lived (certainly the most successful). Continuing the fight would have put McGregor at risk for continued head trauma, risking a future of chronic traumatic encephalopathy, or at worst, repetitive damage leading to a severe traumatic brain injury such as a brain bleed. It wouldn't be the first time a boxer experienced this, as was tragically the case just this year to young Daniel Franco, who required emergency neurosurgery to save his life.

Darragh O'Carroll, MD, is a former ringside doctor and an emergency physician in Hawaii.

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