It's that time of the year again: concussion season. The major sports with the highest incidence of head injuries are all in full swing, including football, hockey, and european soccer. Many fans have heard sports news anchors saying a certain concussed athlete passed or failed an ImPACT test, but few may understand what that really means. What are we actually testing, and why do we need to do it?
The basic idea behind testing concussed athletes before they are allowed to return to play is that concussions are thought to put the brain in a vulnerable state. Consequently, sustaining another concussion before recovering from the first may put the athlete at risk for further and more serious injury. Determining recovery from concussion is very difficult, however. We can't rely solely on athletes reporting symptoms they are experiencing for a couple of reasons. First, they are often motivated (and pressured by coaches and teammates) to minimize symptoms so they can get back into the game. Second, subtle neuropsychological difficulties may still be present in the absence of physiological symptoms. Thus, objective measures are needed to assess the presence of any subtle problems resulting from concussions. This is where ImPACT and other similar tests come in.
Immediate Post-Concussion Assessment and Cognitive Testing (ImPACT; ImPACT applications) is a brief, computerized test battery designed to measure domains often impaired in concussed individuals, including memory, processing speed, and reaction time (anyone who is interested in getting a sense of what the test is like can try a demo here). The test is not "pass or fail", despite how some refer to it on the news. Athletes typically take the test when healthy to establish a baseline score. After suffering a concussion, they take the test again, and the results are then compared to their baseline scores. If post-injury scores are significantly lower than baseline scores, then it is concluded that full recovery has not yet occurred.
One important thing to note is that these tests do not diagnose concussions. What they are doing is essentially assessing for declines in neurocognitive functioning and attributing them to the effects of the concussion on the brain. Another fact to keep in mind is that these tests are far from perfect. The baseline-testing paradigm described here is standard practice across many sports and competition levels, but it is also quite controversial. There are a number of problems associated with this model, which I'll talk about in another post...