Moving towards concussion biomarkers
Concussion is a tricky diagnosis to make. Why? Because it is a 100 percent guess.
Let me elaborate. There is no diagnostic test for concussion. There is no way that any healthcare professional, no matter their level of expertise, can tell you, with any type of certainty, that you have suffered a concussion. Just like no one can tell you that you have not suffered a concussion. This may surprise you.
Concussion is what is called a “clinical diagnosis”, which simply means that it is based on having some sort of mechanism of injury (i.e., a hit or a fall) followed shortly thereafter by signs or symptoms indicative of a concussion. If the healthcare professional cannot reasonably conclude that the symptoms you are experiencing are from some other pathology, then the likely diagnosis would be concussion. The tricky part is that the symptoms are not specific to concussion – meaning that other conditions, such as whiplash, anxiety, low blood sugar, physical fatigue, dehydration, etc., cause many of the same symptoms. This makes concussion almost a diagnosis of exclusion. If it’s not any of these other things, then it is likely a concussion.
These symptoms however, are also self-reported, which obviously causes problems in the medico-legal and insurance world where it can be very easy for an individual to report having these symptoms when they do not. And, since there is no way to actually confirm that a concussion has happened, there is no way to prove that someone is not feeling what they say they are feeling.
Enter concussion biomarkers. A biomarker is some marker or “proof” that a concussion has occurred. This can be special imaging, certain tests, proteins found in blood or saliva, or other physical/cognitive tests. For example, when you have a heart attack, there are certain characteristic changes that occur on ECG (AKA EKG) and there is also a compound released into the blood stream which is detectible on a blood test. Wouldn’t it be great if we had something like this for concussion?
Well we might not be far off! Several advancements over the past five years have led to improved imaging technology which can examine how a brain is functioning. This allows researchers, and one day, clinicians, to have more insight into concussion injuries, which are invisible on current imaging technologies like MRI and CT scans. Researchers are also working hard to find blood tests and saliva tests which may be able to eventually confirm that a concussion has occurred. While none of these technologies or tests can currently confirm a concussion has occurred, we are moving in the right direction. As research continues to explode in this field, it is only a matter of time before we find a viable and reliable option.
One major barrier to finding a good confirmatory test is the fact that we don’t have a “gold standard”. A gold standard is generally required in the development of any new diagnostic test in order to confirm the diagnosis and see how well your new test picked it up. As an example, I will use ACL tears in the knee. The ACL is a big ligament in your knee which prevents your lower leg from sliding forward on your femur. The “gold standard” for diagnosing an ACL tear is arthroscopic surgery; if a surgeon can visualize that the ligament is torn, then it is torn – diagnosis confirmed, although a very impractical way to make it (i.e., every person having to get surgery!). So we have MRI. MRI is not as good as surgery, but to see how good MRI is at picking up ACL tears, you would run a study where people got MRI and surgery and see how accurate the MRI was. If it is almost as good, then the MRI can be considered a good test for diagnosing ACL tears.
With concussion however, we don’t have a gold standard. We don’t have any surgery where we can go in and visualize a concussion. If we can’t confirm that it’s occurred, it becomes very difficult for the development of any tests because even if certain findings are present on functional imaging or certain blood markers are present in the blood, how do we know that is due to concussion and not some other injury? Tricky, Tricky!
In summary, we are working towards finding biomarkers for concussion, but the road may be long and winding.
To read the number four concussion breakthrough in the past five years, click here!