Concussion Baseline Testing

Concussion baseline testing is the process of testing the uninjured brain so that there are normal values to refer to in the event of a brain injury.  This is important because concussion is heterogeneous, meaning it is different for every person due to the uniqueness of every brain.  The many categories of concussion, also discussed in a previous article, require assessments to be thorough, covering the various subtypes of cognitive, headache/migraine, vestibular, oculomotor, and mood disorders, along with the associated disorders of sleep and cervical strain.

When somebody presents to a clinician with a concussion, scores and tangible measures should be recorded, where able, aiming to measure the severity of the symptoms in each category.  From these scores, the progress of the concussion can be compared to the initial scores, indicating the change over time.  Comparing these scores over time will help decision-making regarding the effectiveness of treatment, and the prognosis regarding recovery and recovery times.

When can I go back to sport?

A question that is often hard to answer is, “when is the concussion fully recovered?”.  Often the decision-maker must navigate the motives of the coach, club, and the athlete, whilst keeping in mind the ultimate safety of the player

And the reality is that often we will never know when the impairments of the brain injury are back to pre-injury levels…. because we never knew what pre-injury levels were!

UNLESS… that person was pro-active and foresighted enough to have done a BASELINE test.

Baseline tests take some of the guessing game out of the very important decision regarding recovery and returning to sport.  Huge amounts of research in recent years have pointed towards previously unrecognized effects of brain injury in sport.  Awareness of the debilitating effects of concussion has increased so much that the average rest time (regarding playing sport) in the last two decades has changed from 3 days to 12 days, and it is likely to continue in the same direction. (1)

We know how important it is to avoid the catastrophic situation of repeated and accumulative head injuries, or even worse, the second impact syndrome and so generally, returning to sport does not occur before all symptoms have resolved.  Yet at some stage, somebody must make the decision about when is it is safe to return to activity, exercise, or sport.

Baseline testing is a proactive step towards risk management in head injury, but research also shows that the implementation of baseline testing brings with it the added benefit of improving awareness and decision making in the event of a concussion. (2)

A well-informed decision about when is a safe time for a player to return to sport must include more than just the subjective report of the injured person, i.e., there needs to be more than the simple question of “how do you feel?”.  Athletes may give false statements about their symptoms, misleading clinicians purposely to return to sport, and symptoms alone may not be a great indicator that a brain has recovered.  Objective measures are needed as well as subjective reports from the athlete.

Objective measures of cognitive function

Neurocognitive baseline testing was introduced in the 1980s.  Since then, it has evolved into the form of computerised testing and is now recognized as a cornerstone of concussion management.  Cognitive testing has traditionally been the gold standard for objective baseline testing yet studies over time have debated the validity of baseline testing, with concerns around things such as performance validity.  “Performance validity is defined as the extent to which test-taking behaviour provides an accurate reflection of the underlying cognitive ability that the instrument was designed to measure.” (3)

Reasons that the tests may be inaccurate include “sandbagging” (deliberately under-achieving), and age-related change in attention and cognitive development.  It is estimated that 10–12-year-old participants have a poor performance validity, but this improves as participants reach 21 years old. (3)

Many Australian teams use the HeadSmart app, which is designed to be an easily accessible and ready-to-use sideline assessment.  It has been designed by an Australian-based Doctor of sports medicine, Ryan Kohler.  Dr. Kohler is recognized as an expert in concussions.

Being FDA approved, the American-based ImPACT neurocognitive assessment is perhaps the most widely used form of neurocognitive baseline testing.  Due to its popularity, several studies have been done to look at the usefulness and reliability of the ImPACT assessment.  Results point to questionable outcomes due to a range of variables, with reliability being higher for reaction speed and visual-motor speed than memory components of the test.  The general conclusion is that it is only partially reliable as a concussion screening tool and that it should also be used on a case-to-case basis. (diagram below shows Impact screenshots)

There is also Cognigram and multiple other digital tests available for tracking cognitive performance, however, many of these tests all come at a cost of approximately $20-30 AUD for baseline and post-injury assessments.  The DSST, developed several decades ago, is a simpler test and although it does not specifically test different regions of the brain, performance relies on a combination of motor speed, attention, scanning, and learning (see diagram, showing the DSST test).  It is not available in digital form, making its application a little user-unfriendly, but it is inexpensive and “is a valid and sensitive measure of cognitive dysfunction impacted by many domains.” (4)

Regardless of which cognitive assessment is being used, cognition remains only part of the concussion presentation, and therefore measuring cognition remains only part of the overall measurement of concussion.

The bottom line is that neurocognitive testing forms only part of the “multifaceted concussion-management program that uses all appropriate tools in clinical decision making.” (5).

Broadening the measurement of baseline testing

Balance:

The most thorough baseline assessment should theoretically support the most thorough assessment of concussion and include the broadest range of available investigations.  These measures may come in the form of clinical examinations, subjective symptom reports, emotional states, cognitive testing, eye-tracking, and balance assessment.

Balance is an output of visual, vestibular, and proprioceptive inputs, processed by the brain, and therefore by being a function of the brain, it can be used to assess brain injury.    Currently, the BESS assessment of balance is often used to assess balance performance, however, the balance question remains around how long balance dysfunction will continue, post-injury, and therefore it also has limited reliability. (6)

Oculomotor:

Studies show that there is a high proportion of involvement of the oculomotor system after a concussion.  The King-Devick test captures impairments in eye movements and was originally developed as a pencil and paper test (see diagram below).  It has been researched and proven to be a reliable test after head injury. (7)

The growing awareness of oculomotor dysfunction following head injury has prompted a commercial movement towards the use of recent technological advances in eye-tracking to become a form of brain function measurement and baseline testing.  There are now commercially available eye-tracking devices, such as the Right-eye , which enable accurate, objective measurements of eye movement, beyond what the naked eye can see (see example below).  An advantage of the eye-tracking assessment is that it is obvious if the test-taker is purposely under-performing on the assessment, adding to its reliability as a screening tool.  Overall, there is a rising awareness, growing availability, and underlying need to include oculomotor assessments as part of concussion assessments, and this will only continue as technology allows more accessible instruments in this field. (8)

Baseline testing – the conclusion

In conclusion, the variety of tests available for brain function make some form of baseline testing possible with affordable and simple pencil and paper tests.  More advanced (and more expensive) “high-tech”, digital testing offers more features such as objective data, patient management databases, and remote testing, and comes in the form of computerized eye-tracking, online cognitive tests, and digital force-plate balance assessments.

The right choice will depend on a range of variables such as the risk of head injury, finances, beliefs, available time, and values, to name a few.  The logical thinking, and what the research indicates, is that a broader variety of tests, including multiple functions of the brain, give the most information about pre-injury brain function.  Of course, this then gives the most information about post-injury comparisons, to assist high-stake decision making.

How much is your brain worth?

Regards

Paul Michael