Frequently after a bump, bruise, jostle, or some impact to the head or skull a medical professional or witness to the event may diagnose a “mild” traumatic brain injury (TBI) or a “mild” concussion. When people hear the term “mild” they typically conclude that the injury is not serious, it will not persist, and the individual will make a full and complete recovery from a TBI. Unfortunately, new research performed at the University of Pennsylvania is casting doubt on the belief that a brain injury or concussion can every truly be characterized as “mild.” Furthermore, the study, SNTF Immunostaining Reveals Previously Undetected Axonal Pathology In Traumatic Brain Injury calls into question the sufficiency of medical treatment, if any, that is typically administered following a traumatic brain injury.
How was a “Mild” Concussion or TBI Defined Traditionally?
Considering the pace of advancement regarding our understanding of brain injuries, use of the term “traditionally” might seem out of place, but we are nevertheless moving away from a definition of a mild TBI that is increasingly insufficient. If the study’s findings are proved out, it may turn out that the terms “mild” and “traumatic brain injury” are contradictory and mutually exclusive.
In any case, a mild traumatic brain injury was typically diagnosed after an individual had suffered a brief loss of consciousness or a brief interruption in normal brain functioning due to an impact to the head or skull. In the past, a coach or athletic trainer may have described the event and injury as the player having his or her “bell rung.” Typically, little to no medical treatment would follow events of this type. At most, the individual would sit out for the practice, game, or another event. Victims of a “mild” traumatic brain injury often do not seek further medical attention despite the fact that other studies suggest that approximately 20 percent of sufferers experience cognitive defects for two to three months or longer.
Perhaps part of the reason behind our relatively cavalier attitude regarding traumatic brain injuries can be attributed to the fact that, until recently, we had little understanding of the mechanism of injury occurring in the brain. However, this new UPenn study purports to offer an explanation regarding what happens in the brain when a TBI is sustained, methods to detect a TBI, and the likelihood for long-term recovery after a brain injury.
Even Mild TBI’s are Diffuse Axonal Injuries
For years the exact mechanism of injury in a mild brain injury has not been well-understood. After all, TBIs previously considered mild did not present obvious signs of damage such as bleeding, bruising, or other damage on MRIs or CT scans. This study asserts that the damage caused during a mild concussion occurs in the white matter of the brain due to the stretching, swelling, and detachment of axons. The study believes that mild concussions also cause diffuse axonal injuries though the severity is less than what occurs in a moderate or severe TBI.
A diffuse axonal injury occurs when the brain is subjected to violent and rapidly changing forces. These forces can stretch, deform, and damage axons. However, the destruction of axons rarely occurs at the moment of impact. Rather, many axons are able to draw on stores of sodium and calcium to repair and restore function. However, when the injury is particularly severe, certain axons may have calcium concentrations rise to levels where the axon, essentially, self-destructs. When the axon self-destructs certain protein-breaking enzymes are released leading to the structural degradation of the axon and its detachment from the brain. When an axon detaches from the brain’s nerve fibers, it will not regenerate.
Axon Destruction Enzyme Could be Used to Test for Brain Injuries
Past research has shown that the presence of the axon-destroying enzyme leaves telltale signs. One of these signs is an SNTF (alpha II-spectrin N-terminal fragment) which may be useful as a biomarker to detect the presence of a traumatic brain injury. Additionally, the research also focused on the presence of APP, a protein that is often observed following a brain injury. Despite both substances appearing after a brain injury, there was surprisingly little overlap between them.
The study authors believe that this finding can be explained by different functions they believe that each potential marker serves. They hypothesize that SNTF can be used to identify when axons have suffered sufficient damage to enter into the self-destruct process. They believe that APP is present when axons have sustained damage, but will be able to repair themselves.
According to one of the researchers of the study, “We’re starting to believe that the term ‘mild traumatic brain injury’ is an oxymoron. For some people, there’s nothing mild about it.”