Classifying TBI as Mild, Moderate or Severe is Outdated and Counterproductive
The August issue of the Journal of the American Medical Association (JAMA) includes a “Viewpoint” by two leading neuroscientists promoting the use of an “International Knowledge-Based Approach” to traumatic brain injury (TBI).
One of the causes of the failure of clinical trials to successfully treat TBI, the authors contend, is the common classification of TBIs as “mild, moderate or severe.” These classifications do not incorporate newer insights and findings from diagnostic tools such as imaging and biomarkers and therefore do not promote “mechanistic targeting” for clinical trials. The authors support the transition to a more nuanced approach, a precise disease classification model that is based on the precise pathoanatomical and molecular features of the injury.
As discussed in my previous post on “Meta- Analysis,” the existing classification approach lumps TBIs into the mild, moderate or severe category based on acute symptoms, such as length of unconsciousness or alteration of consciousness, or Glasgow Coma Scale, and assumes that all injuries with similar symptoms will follow a similar course. In other words, brain injuries are treated as “homogeneous” when we know from research over the last several years that they are very “heterogeneous.”
As we have gained more ability to measure brain pathology following injury, it makes more sense to focus on the actual injury, not just the acute symptoms.
One study the authors point to as holding promise for providing a more useful approach is a 2013 study by Yuh, et al, in the Annals of Neurology where magnetic imaging uncovered structural abnormalities in approximately 30% of 135 patients with mild TBI and a normal computed tomographic (CT) scan. The presence of these abnormalities predicted an unfavorable outcome at three months. “This study,” the author of the Viewpoint say, “represents an important step toward improved stratification of heterogeneous patient subgroups within the population traditionally classified as having mild TBI or concussion.”
Another development referred to by the authors has also been discussed in this blog, the newly validated blood-based glial proteomic biomarkers which have been shown to reliably detect the presence and severity of brain injury seen on CT scan.
Progress towards a more nuanced approach to TBI continued with a very recent October 2013 article in the Journal of Neurotrauma presenting evidence that there are genetic influences on the outcome following a TBI, impacting the neuroinflammatory processes that contribute to the severity of outcome.
It is time to move beyond the unproductive use of terms like “mild, moderate and severe” and develop an approach that takes advantage of our growing understanding of the brain and its response to trauma.