Baseline Testing for Concussion: What it is and what it isn't
Baseline testing for concussion is a measure of a persons neurological function prior to sustaining a concussion. We will get more into what exactly that entails, but to understand it's purpose and appreciate its importance, we have to go back in time...
A little about the history
The purpose and importance of baseline testing began with the Pittsburg Steelers' Merril Hoge. Hoge was a running back for the Steelers from 1987 until 1994, when he went to play for the Chicago Bears. As a professional football player, he had suffered multiple concussions throughout his career. However, while playing for the Bears in 1994, he sustained a concussion that would later end his career. After Hoge's first concussion with the Bears, a medical doctor cleared him to return to play just days later. It is unclear how this provider made their decision; however, according to Hoge, the assessment to return to play took place during a conversation over the phone. A few weeks later, Hoge sustained yet another concussion and went into cardiac arrest. Fortunately, he survived after treatment in intensive care; but, not without long-term consequences. After several weeks from his near-death concussive event in 1994, Hogue was still experiencing persisting concussive symptoms. Dr. Joe Maroon of the Pittsburg Steelers assessed Hoge's neurocognitive function and determined he was significantly impaired compared to....his baseline! But how did they know what Hoge's baseline was?
In 1990, Steelers Coach Chuck Noll prompted Dr. Joe Maroon, team neurosurgeon, and Dr. Mark Lovell, a neuropsychologist, to develop a test that would establish an person's neurocognitive function at baseline, or prior to sustaining a sport-related concussion. This test is known as ImPACT (immediate post-concussion assessment and cognitive testing). In 1991-92, Maroon and Lovell administered this test on the entire Steelers team, including Hoge. Having Hoge's baseline from 1991, allowed Maroon to discern if he was fully recovered from his most recent concussions years later. It was determined that he was not, and that sustaining more concussions could potentially threaten his life. Hoge immediately retired.
So what is baseline testing?
As in the example above, baseline testing guides medical decisions for when a person is fully recovered from their concussion and is safe to their activities. The neurocognitive testing developed by Maroon and Lovell gives medical providers insight into a person's visual and verbal memory, reaction time, and processing speed. Without this, the person may appear to be recovered, and may even report no symptoms, but cognitively, their reaction times or processing speed may be slower, increasing their likelihood of sustaining yet another concussion. Is testing neurocognitive function enough information to let us know when a someone is ready to return to their sport or hobby?
Statistically, ImPACT testing does have a high sensitivity (81.9%) and specificity (89.4%) meaning that the test accurately identifies those who truly did have a concussion 81.9% of the time and those who truly did not have a concussion 89.4% of the time (1). However, there are reasons other than being concussed in which a person might perform poorly on neurocognitive testing such as poor sleep, low motivation, or drug and alcohol use. Similarly, people with a concussion may only report symptoms of dizziness, headache, or imbalance, not related to cognitive dysfunction. With this in mind, the current recommendation is to use multiple types of tests, or a comprehensive battery of tests, when performing baseline testing for concussion in order to assess these other symptoms or impairments (2).
Four tests are better than one
At Whidbey Dizziness & Balance, I use a battery of four tests for baseline testing for concussion. In addition to providing neurocognitive testing using ImPACT, I assess oculomotor function (eye movement/control), vestibular function (spatial awareness/dizziness), and balance. I also utilize a self-reported symptom measure to give the person an opportunity to report any persisting concussive symptoms. This allows me to make evidence-based recommendations to doctors, athletic trainers, coaches, employers, and patients for when a person is ready to return to their sport, hobby, or job.
Dispelling the myths of baseline testing
Knowing what baseline testing is not is just as important as knowing what baseline testing is. Go ahead and test your knowledge of baseline testing.
TRUE or FALSE
Baseline testing for concussion is only for athletes.
FALSE - Baseline testing can be used for anyone to establish their baseline neurocognitive, oculomotor, vestibular, or balance function. In fact, ImPACT neurocognitive testing is normed for ages 12-80 years old. Having your baseline can help medical professionals determine when you are ready to return to a specific activity (biking, rock climbing) or to work in high risk environments (commercial fishing, construction, logging).
Baseline tests can diagnose a concussion.
FALSE - While there has been exciting advances the use of biomarkers to diagnose concussion, we currently we do not have a widely-used, definitive test, including imaging. https://www.sciencedaily.com/releases/2021/03/210323183823.htm
All my athletes have a baseline test, so my concussion management program is complete!
FALSE - Baseline testing is just the beginning...establishing the baseline. A complete concussion management program needs to include a method of detecting and reporting a concussion on the sideline, comprehensive recovery protocols for return to play (and learn), communication plan among parents, coaches, athletic trainers, and healthcare providers, and ongoing education of everyone involved in the detection and management of concussive symptoms.
I've had a baseline test, so I don't need another one.
FALSE - Firstly, make sure the baseline test you completed was a comprehensive battery of tests and not just one test. It should include neurocognitive function, balance assessment, and vestibular and oculomotor function. In addition, as we age through adolescence, our brains are growing and developing, so your baseline test when you were 12 may not be the same as your baseline test when you are 16. Therefore, it is recommended athletes undergo baseline testing annually.
I don't need to have another test after my concussion in order to return to play.
TRUE - Guidelines (2) state that neurocognitive testing after a concussion is not required to successfully manage return to play decisions. However, this is assuming the athlete has successfully completed a comprehensive rehabilitation program which may include: vestibular rehabilitation, balance training, vision therapy, and exercise stress testing. At Whidbey Dizziness & Balance, I have my athletes complete an exercise stress test, along with sport-specific vestibular, oculomotor, balance, and coordination exercises in order to make return to play recommendations. In cases where I cannot stress the athlete's system in the clinic as would be in their specific sport, I may chose to use post-injury neurocognitive testing, along with a vestibular, balance, and oculomotor test battery, to make my recommendation.
Why is baseline testing so important?
In extreme cases, like the one with Merril Hoge, the use of baseline testing potentially saved his life. But, more commonly, baseline testing provides more clarity for healthcare providers when making critical return to play/activity/work decisions. This may prevent a person from sustaining a second concussion prior to healing from their first, and experiencing more severe, persisting concussive symptoms. If you participate in activities, hobbies, or sports that place you at risk for a concussion, book a baseline test to ensure full and safe recovery after your concussion.
Schatz P, Pardini JE, Lovell MR, Collins MW, Podell K. Sensitivity and specificity of the ImPACT Test Battery for concussion in athletes. Archives of Clinical Neuropsychology. 2006;21(1):91-99.
McCrory P, Meeuwisse WH, Aubry M, et al. Consensus statement on concussion in sport: the 4(th) International Conference on Concussion in Sport held in Zurich, November 2012. J Am Coll Surg 2013;216:e55–71.