Defining Mild Traumatic Brain Injury (mTBI)

The current issue of the European Journal of Neurology has an article on how to classify mild cases of Traumatic Brain Injury, or mTBI. Using the words mild and traumatic in the same definition seems a bit of an oxymoron, but the author reasonably uses the European Federation of Neurological Societies’ definition, which sets the bar with two main criteria: (1) Loss of Consciousness (LOC) and (2) Post-traumatic Amnesia (PTA).

In other words, if a TBI event does not include 1 & 2 above, then it is classified as a head injury. The next level of severity, mTBI, includes LOC for less than 30 minutes and PTA for less than one hour, at least by the European Journal of Neurology standards. Other often used criteria for mTBI include the Glascow Coma Scale (GCS), and the TBI definition from the Head Injury Interdisciplinary Special Interest Group of the American Congress of Rehabilitation Medicine. Since there is a lack of consensus on criteria for mTBI, using different definitions will produce different results at this point.

There are some promising steps being made in diagnosing and treating mTBI with more precision and accuracy. The first step is instituting baseline cognitive assessments for student and professional athletes, along with field diagnostic tools like portable EEG units. Specialized groups like the military and sports teams have taken the lead in baseline cognitive testing and field cognitive diagnostics, and they can serve as a springboard for dissemination to the general public.

Recent research with portable EEG tests on athletes who have received a concussion strongly indicate that EEG patterns do not return to a normal baseline until several weeks after more obvious symptoms like balance and memory problems have subsided. It is this “vulnerability window” between lack of symptoms and EEG baseline resumption that needs to be closely watched — a second TBI in this time window could have far worse effects than the original TBI.