A male patient in his early 30s, seen in the University of Mississippi Medical Center clinic in the summer of 2019, had sustained a head injury above his left eyebrow from a snowboarding accident in December 2017. He presented in our clinic with primary complaints of lightheadedness on a weekly basis, room-spinning vertigo every couple of days, presyncope and syncope every so often, floaters in his vision, and daily imbalance.
Formerly a monthly “migrainer,” he reported that his migraines had doubled since his snowboarding incident. He denied any hearing concerns, a fall within the past 12 months, or the use of a vitamin D supplement. The patient reported that competing speech signals that require “too much brain power” worsened his symptoms. He noted that something that provides him temporary relief is applying pressure to the base of his skull in the form of pressing his head into the back of a chair headrest.
Of note, it is important to mention that the patient’s medical history was also significant for a car accident in 2015. Based on symptomatology, the patient was diagnosed with concussion and referred for a balance assessment.
Upon arrival to his balance assessment, the patient completed a case history packet including the Dizziness Handicap Inventory. He scored a total of 74 (Emotional = 20, Functional = 30, Physical = 24), which was consistent with a severe dizziness handicap. He then completed a balance evaluation including videonystagmography (VNG), video head impulse testing (vHIT), and computerized dynamic posturography (CDP).
Interestingly, the testing was largely within normal limits. There was no presence of spontaneous nystagmus, benign paroxysmal positional vertigo (BPPV), or gaze-evoked nystagmus. Some positional nystagmus was observed in vision-denied conditions, however, it was non-clinically significant in nature. Also interestingly, oculo-motor testing (tracking, random saccades, optokinetics, etc.) was normal.
Caloric irrigation revealed a borderline left unilateral weakness, on the side of the head injury (TABLE 1). Of note, right warm and left cool irrigations were repeated, but they yielded comparable results to the primary irrigations.
|IRRIGATIONS||Left Warm (LW): 12 deg/sec
Left Cool (LC): 6 deg/sec
Right Warm (RW): 20 deg/sec
Right Cool (RC): 11 deg/sec
|UNILATERAL WEAKNESS||27% in the left ear (Normal range < 25%)|
|DIRECTIONAL PREPONDERANCE||6% to the right (Normal range < 30%)|
|FIXATION SUPPRESSION||0% right cool, 35% left warm (Normal range < 50%)|
Video head impulse testing (vHIT) yielded no significant overt or covert catch-up saccades when stimulating the lateral; left anterior, right posterior (LARP); or right anterior, left posterior (RALP) planes.
CDP Testing Performance
Sensory organization testing (SOT) showed his performance as abnormal for Conditions 1–3, the most dynamically straightforward of the SOT conditions. However, for Conditions 4–6, his performance was well within normal limits for the more demanding tasks, launching him into an overall normal composite score regardless of his significant imbalance (FIGURE 1).
For his motor control test (MCT), the size and timing of his responses were within normal limits, but he shifted his body weight heavily to the right (his snowboarding stance) to athletically compensate for any disordered balance issues that would typically be recognized during this test (FIGURE 2).
CDP Testing Results
Sensory Organization Test
Sensory organization testing (SOT) is composed of six increasingly dynamic conditions (three trials each), yielding a composite score averaging the performance on all conditions. The gray backdrop behind each condition (x-axis) in FIGURE 1 represents the range of normal for the degree of sway (y-axis). The blue bars represent normal sway, red bars represent abnormal sway, and striped bars represent trials that were repeated.
The sensory analysis portion of SOT testing assesses how a patient uses inputs from their somatosensory (SOM), visual (VIS), and vestibular (VEST) systems to maintain their balance. During the testing, the visual reference and base of support (BOS) the patient is standing on are disrupted in a systematic fashion, providing atypical inputs the patient has to combat in order to maintain balance.
For strategy analysis, each of the shapes represent a condition. Depending on where they are plotted, they indicate if a patient uses a hip-dominant or ankle-dominant strategy to maintain balance.
In Conditions 1–3 for this particular patient, the surface that he was standing on did not move and he was relying on his own static balance. He demonstrated more sway than what is considered normal. In Conditions 3–6, however, there were varying combinations of moving visual surroundings and base of support, which are typically more difficult to perform, in comparison to Conditions 1–3.
As demonstrated in this patient’s strategy analysis and center of gravity (COG) alignment, he managed to “ride” the machine as if he were back on the slopes, which resulted in the avoidance of an ankle- or hip-dominant strategy reading. The snowboarding term “goofy” is indicative of a right-foot-forward, left-foot-back riding stance, which was apparent in his COG alignment: most of his weight distribution was toward the right.
Motor-control testing assesses a patient’s ability to adapt to sudden and unpredictable forward and backward movements of the platform they are standing on. Three measurements are obtained: weight symmetry between sides (right and left), how long it takes the patient to react to the unexpected movement (latency in milliseconds), and how strong their reaction is (amplitude scaling).
For this test, the shaded areas in FIGURE 2 represent abnormal responses and the white areas represent normal limits. The S, M, and L signify small, medium, and large impulse movements of the platform. The three boxes represent the patient’s performance directly parallel to the S, M, and L movements.
This patient had a tendency to lean heavily to the right during those movements, which reflects his snowboarding stance. The timing (latency) of his response was normal for both medium and large forward and backward movements of the platform, and the size of his response was normal, further solidifying his athletic ability to compensate for any true disruptions to his balance strategies.
Improved performance with increased demand?
Upon testing, what was observed was an athlete doing what he did best: snowboarding. He visibly dropped his hips and bent his knees for the more demanding Conditions 4–6, which allowed him to compensate for the increased dynamics in testing (FIGURE 1). Additionally, this patient adapted and anticipated appropriately when the task was more predictable in nature (FIGURE 3).
The adaptation test presents “toes up” and “toes down” movements of the platform the patient is standing on. There are five trials of each movement (x-axis of the top boxes in FIGURE 3). The shaded region represents abnormal performance.
For each of the conditions, this patient performed within the range of normal (green boxes). The trend for normal balance adaptation is that the “tracings” (second and third figures) get smaller and smoother with each trial because the patient is able to predict and adapt accordingly. Our patient adapted and predicted with each trial that was presented, which is apparent in the increasingly smooth tracings in sway.
SOT Raw Data
The raw data for the patient’s sway and the shear force of the plate during SOT testing are shown in FIGURE 4 for each of the three trials performed for all six conditions. In Conditions 1–3, the patient’s amount of sway was considered abnormal, although these conditions are not as dynamic as Conditions 4–6.
In the first condition, the patient is standing on a still platform with eyes open and the visual reference does not move. This patient had trouble maintaining his base of support (BOS) over his center of gravity (COG). This trend continued in Condition 2 (Condition 1, but with eyes closed) and Condition 3. He responded to dynamic movements by inadvertently bending his knees more, dropping his hips, and using other snowboarding tactics.
The first three conditions of SOT (described in FIGURE 4) are the least dynamic of the six SOT conditions, meaning that the patient is more readily relying on using their functional balance and proprioceptive inputs to maintain their stability. Typically, with patients exhibiting symptoms similar to the patient in this case, the trend seen in SOT performance is as follows: a decline in SOT performance with the progression to each condition. This patient’s performance improved during the most dynamic conditions (4–6) because they triggered his athleticism to initiate compensatory strategies for balance maintenance (see equilibrium score of FIGURE 1).
The CDP testing revealed that the athlete’s sport of choice must be considered in order to accurately determine the functional impact a head injury could have had on their vestibular system. Although a standardized baseline shift could not be applied, it raised speculation as to what additional testing must be performed to appropriately aid in the rehabilitation of a concussed athlete from an auditory perspective.
The vestibular test battery showed overall normal vestibular function, as did CDP, with the exception of the least dynamic SOT conditions. Based on history and complaints, the findings suggest concussion and sub-concussive events.
The auditory system is uniquely situated in the temporal lobe to be ultra-susceptible to external forces applied to the brain, even when mild in nature (Kraus and Krizman, 2018). Changes in sound processing and equilibrium can be monitored via auditory and vestibular testing in athletes before and after sustaining a head injury.
Sports-related concussions have long been on the rise. Approximately 2.5 million high school students reported having had at least one sports-related concussion within the 12 months preceding their response to the 2017 National Youth Risk Behavior Survey, according to the Centers for Disease Control analysis of the survey (Centers for Disease Control and Prevention, 2017). Technology has been evolving to help detect these concussive and sub-concussive events (Kraus and Krizman, 2018).
Traditionally, concussion was only diagnosed when a total loss of consciousness was observed, but it is now known that approximately 95 percent of concussion patients maintain consciousness throughout the duration of the injury (Kraus and Krizman, 2018). According to the Centers for Disease Control (CDC, 2019) and the Defense and Veterans Brain Injury Center (2020), “concussion” and “mild traumatic brain injury” (mTBI) are synonymous, warranting the expansion of the injury scope of a concussion (Kraus and Krizman, 2018).
The accumulation of concussive or sub-concussive events over time leads to chronic traumatic encephalopathy (CTE), a “degenerative brain disease found in athletes, military veterans, and others with a history of repetitive brain trauma,” according to the Boston University CTE Center (2020).
Dr. Bennet Omalu published the first evidence of CTE in 2005, as found in Mike Webster, a center for the Pittsburgh Steelers (Omalu et al, 2005).
Since the discovery of CTE, several studies have uncovered its prevalence in professional and amateur athletes, including a study conducted by Mez et al in 2017. Researchers in this study inspected the postmortem brains of 202 former professional athletes, 111 of which were former National Football League (NFL) players. CTE was found in the brains of 110 of the former NFL players (Mez et al, 2017).
Test Findings and Athletic Abilities
Concussions, particularly mTBI or sub-concussive events, are “invisible injuries that affect function rather than macrostructure” (Kraus and Krizman, 2018). These events go unseen using conventional imaging, such as a computerized tomography scan (CT scan) or magnetic resonance imaging (MRI), and diagnosis relies heavily on symptom reporting (Kraus and Krizman, 2018).
What, then, potentially becomes the issue when relying on symptom-reporting from amateur or professional athletes? They might be inclined to brush off lightheadedness, double vision, or loss of concentration for the sake of the game, a scholarship, or not disappointing their team.
CDP has been proposed as a concussion detector in studies, including research conducted by Karin et al in 2017. That research team quantified the impairment of a concussion on five male athletes in order to implement more targeted therapy techniques. In the study, post-therapy posturography showed an average of a 22 percent improvement in the overall CDP composite score (Karin et al, 2017).
Previous studies have demonstrated how CDP can be used as a tool to quantify the impact a head injury has on balance, post mTBI (Walker et al, 2018). Additional studies have looked into the test-retest reliability of the addition of a head shake (HS) during sensory organization testing (SOT) of post-concussed athletes to detract from the athleticism supplementing their performance (Cripps et al, 2016). Our facility currently does not have a post-concussion protocol that includes HS-SOT.
Overall, our findings in this case study of a snowboarder suggest that providers must be cognizant of the way athletic ability may alter test findings.
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