Common Tread

Ask the doc: Can off-road racers suffer brain trauma even before they crash?

Mar 01, 2018

Crashing a motorcycle is a good way to get a concussion and repetitive impacts are linked to chronic traumatic encephalopathy (CTE). Is CTE an issue with motorcycle racers? Even when they don't crash?

CTE has been highlighted in former boxers, professional wrestlers, and U.S. football (not soccer) players. CTE has been cited as occurring in 110 of 111 former football players whose brains were donated for research and was diagnosed in 87 percent of 202 players in another study, including high school and professional football players.

The most common cause of death related to CTE (27 percent of all deaths) was from suicide — an event not limited to the elderly. Suicide was generally preceded by impulsivity and anxiety in the early stages of CTE while serious mood disorders, speech disorders, memory failure, and motor dysfunction characterize the more advanced stages. Grim stuff.

Like football players, off-road motorcycle racers wear helmets and have repetitive impacts. In doubt? Watch the short video below and consider the pounding a rider takes just traversing a motocross circuit. Does CTE occur in motorcyclists?

Concussions caused by crashes ended Josh Day’s racing career and convinced motocrosser Davi Millsaps to retire a year earlier than he planned or wanted. But what about the ones that are not so obvious? Do motocrossers sustain repetitive minor concussions? We haven't looked real hard at that one, but the likelihood is yes.

How the brain heals from an impact

Lets take a closer look at traumatic brain injury (TBI) and what happens after an impact injury.

Impact TBI is decreased when you wear a helmet — simple physics — as the helmet dissipates some of the energy that is being transmitted to your skull and then to your brain. The energy that does get through may create bleeding around the brain, bleeding in the brain, and direct injury to the cells that are arranged along the brain’s surface, as well as their delicate extensions that connect outside of the brain. Those connections go to places like your spinal cord. The specific function that each part of your brain controls has been mapped along its surface, as well as from side to side. As you move from the surface (grey matter) to the interior (white matter), the nerve fibers from each cell become increasingly tightly packed together. They are most densely packed in your brainstem. This means that impacts in different areas may have more limited or more widespread effects, even if the same amount of energy is delivered. Even small brainstem injuries wipe out lots of nerve fibers and are generally devastating.

The most common kind of TBI is a concussion. Most of us have had one, and they have three grades from minimal (hit in the head with a basketball) to moderate (kneed in the head during pick-up football, leading to headache and a little dizziness that passes when you get up) to severe (unconscious for a few minutes, disoriented, nauseated, light-sensitive). Nearly all resolve without needing therapy. If you pass out, you should go to the Emergency Department and get checked out, especially if you have had a prior TBI, are on blood thinners, aspirin, or have any kind of cardiac problem (sometimes an abnormal rhythm will also make you pass out).

Davi Millsaps
Davi Millsaps reluctantly decided to retire early rather than risk lasting damage from another concussion. Yamaha photo.
It's likely that motocrossers sustain repetitive minor concussions. What level? Probably minimal for riding and moderate when crashing. However, those designations were derived for a single episode of impact, and they were meant to highlight an expected course of recovery and outcome. We expect people with a minimal concussion to get better without any care; moderate concussion patients often need a day of rest from activity. These diagnoses are not meant for repetitive impacts in a short period of time. We are not sure what they mean for individuals who sustain them — but we are learning.

Recovery means that the brain must heal. Nope, you do not grow new brain cells if some die, and the remaining ones do not get better at their jobs. You can, on the other hand, teach them how to do a job they did not previously do. This is termed “plasticity” and it happens more often and more rapidly in the young. In order for this to occur, blood must be absorbed, tissue-injury-induced inflammation needs to recede, and the brain must be stimulated.

Jose Pascual, MD, PhD, FACS, FCCM is a trauma and critical care surgeon-scientist who is also a neurointensivist with an interest in TBI recovery. His lab is investigating how to aid recovery after impact injury using a modified form of heparin that has limited anticoagulation potential, but lots of anti-inflammatory power. Remember, heparin is what you get in the hospital to prevent clots in your legs; only the unmodified form is available for use in the hospital right now. Promoting bleeding after TBI is thought to be bad and is why this drug is generally not given right after brain injury (no aspirin after your concussion, either, as it also promotes bleeding). Of course, right after injury is when you trigger most of the inflammation and when an anti-inflammatory would be potentially most helpful. This is exactly what he found!

According to Dr. Pascual, an injured brain attracts cells that are typically involved in fighting infection to the site of injury, a process called “trafficking.” While what they do to bacteria is helpful, the inflammation they cause may impair the brain’s ability to heal. Giving injured rodents the modified heparin reduced inflammation, supported more normal blood flow and most importantly, enabled the rodents to perform better on neurologic testing. He is in the midst of planning a human trial to see if this approach helps us recover after brain injury, as well.

Recovery is aided by participating in a multi-modality rehab program that triggers your brain to adapt to any deficits; humans only, there is no rodent rehab. But we don't test every professional or amateur rider for deficits after motocross competitions. Earlier this year, MotoAmerica announced a more robust and three-part testing approach to detect concussions in riders. What we do not know is the threshold for this approach. Will it pick up all abnormalities? Will it detect problems only after they are already established? Can it help recognize individuals with some injury who are at risk of injury progression? We don't yet know how to answer these questions.

Here are some that only you can answer. Would you voluntarily get tested before your next competition to establish a baseline, and then again after each competition for a season to track changes? Would you stop if we found changes only on testing if it did not impact your riding? Do you even want to know?