Incentivization and cognitive performance in those who sustain mild traumatic brain injury: A series of case studies of aviation-rated Army personnel

2.1 Definition of aeromedical (AM) evaluation

For the below cases, each evaluation was conducted for purposes of ascertaining fitness for Flying Duty within the US Army. Although there are many circumstances that can disqualify individuals from Flying Duty in the US Army, both physical and emotional, cognitive health is requisite as well. Brain injury, of any degree, disqualifies one for Flying Duty. Such disqualification is permanent for moderate and severe injuries, but can be waived for mild injuries characterized by concussion or mTBI should the correct authority indicate a waiver is appropriate. Appropriate authority is defined as a clinical neuropsychologist who has also completed AM training. Standards for fitness for Flying Duties, as well as waiver procedures for mTBI can be found in US Army Standards of Medical Fitness, Regulation 40–501, and US Army Aeromedical Policy Letters and Technical Bulletins (AR 40–501, 2017; Aeromedical Policy Letters, 2015). Standards are the same for individuals who once held flight status but had that revoked due to injury and those that never had flight status but are applying who have a history of mTBI.

2.2 Description of case reports

The case reports are presented in the following format: (1) basic demographics and presenting concerns, (2) nature of injury/why “grounded” or initially precluded from flying, (3) accompanying occupational, medical, academic and social histories (4) tests given with results, and (5) summary, recommendations, and conclusion of each case. Although personality testing was given, no interpretation is provided here. None of the cases had a psychological history, and the results of personality testing had no bearing on overall recommendation to obtain or retain Flight Status.

2.3 Battery of tests

Test selection for each case was done using a flexible approach due to the varying needs of the evaluation. For each case test selection is specified.

For each case an estimate of premorbid functioning was used as a decision-making tool. Estimates of premorbid intellectual functioning were taken from scores on the Armed Services Vocational Aptitude Battery (ASVAB). The ASVAB is a multiple-choice test, used by the US Military entrance Processing Center to determine entrance eligibility and occupational placement. The test is a compilation of various achievement tests which measure arithmetic reasoning, general science knowledge, verbal reading and comprehension skills and other abilities and skills. It is designed similar to conventional intellectual tests in that verbal and nonverbal abilities are heavily weighted. In fact, the ASVAB has long been used as an accurate predictor of premorbid intelligence, and correlation with traditional IQ tests have been as high as .92 when corrected for range restriction (military entrance criteria) and reliability estimates (Orme, Brehm & Ree, 2001). Overall General Technical (GT) score was used, which is a compilation of one’s performance on Word Knowledge, Paragraph Comprehension, Arithmetic Reasoning and Mechanical Comprehension scores. Scaling of test is similar to traditional intelligence tests (Wechsler Scales of Intelligence) and has a mean of 100 and standard deviation of 15. Very low scores (below 80) are excluded in that applying candidates with such scores do not meet military entrance criteria.

2.4 Incentivization

Although there are obvious internal motivators involved in candidates for flying duty (self-identification and occupational identity as “pilot” or “pilot-in-training”, derived pleasure from flying) the focus on this project lies in that each had financial incentives linked with re-obtaining their flying status. In the US Army Pilots and Aviation-rated crewmembers receive additional pay for being on flight status which can be substantial depending on rank and time spent in service (Aviation Incentive Pay and Aeromedical Waivers, 2021). In addition, each case read and signed a thorough Informed Consent form which outlined the reason and rationale for the evaluation. Each case was thoroughly aware their return to flight study was at least partially contingent upon their cognitive performance during the evaluation.

2.5 Norms used for IQ comparison and interpretation

Any discussion of cognitive performance in pilots would be incomplete without considering the normative data used for comparison. Research has shown that pilot IQ norms are above those found in the average population. In a study of over 25,000 pilot trainees, King and colleagues (King, Barto, Ree, Teachout, 2011) found FSIQ, Verbal IQ, and Performance IQ means of 120.59 (SD = 6.63), 119.26 (6.7), and 119.22 (8.34) respectively, on the Multidimensional Aptitude Battery-II (MAB-II) for Air Force (AF) pilot trainees. The MAB-II is an intelligence test heavily patterned after and highly correlated with the Wechsler Adult Intelligence Scales (King et al, 2011). However, the MAB-II does not offer specific processing speed (PS) or working memory (WM) subtests for comparison. Such norms were considered and used as comparison for the cases below. Due to the lack of specific pilot-norms on other the NP tests used, no specific pilot-norms were used for comparison.

3.1 Case 1

Case number one was a male in his early thirties at the time of the evaluation. He was employed by the US Army and served as a helicopter pilot. He was referred for an AM NP evaluation after sustaining a mTBI approximately four months prior. He had no presenting concerns at the time and considered himself fully recovered.

His injury occurred when riding his motorcycle home from work and lost control at approximately 35 mph. The patient was helmeted and fully clothed in Army-required motorcycle riding gear (full helmet with face guard, long pants, sleeves, and full gloves). He fell on his left side, and fractured his clavicle, scapula, and sacrum. He hit his head and lost consciousness for a “few seconds.” Emergency services medical records indicate he was awake and alert when ER crews arrived, but estimated time of arrival was not noted. He recalled memories after the accident and Post-Traumatic Amnesia (PTA) was not reported. Glascow coma scale was 15 at ER arrival. CT scans were not done at the time of the initial ER visit. MRI scans were done two months after injury which revealed no significant findings. There were mild complications to recovery in that he had continual report of symptoms suggesting 4th cranial nerve palsy, though this resolved approximately two months post-injury. At the time of the evaluation, he was medically cleared of these problems and considered fully-fit to return to flying responsibilities (pending AM NP evaluation).

Other biopsychosocial information for this subject were unremarkable. He had recovered well from the injuries listed above and had no complicating medical history. He rarely used alcohol, had no history of alcohol-related problems, and denied use since his injury. He denied significant post-concussive symptoms such as vestibular problems, headaches, nausea, etc. His psychiatric history was unremarkable; he had never visited or been treated for any mental health condition. Occupationally, he had no significant problems or history. He had positive relationships with his peers, served multiple, additional roles other than pilot and had no disciplinary action taken against him at any point in his career. Upon his return from injury he showed no functional problems at work, and had passed his Flight Management System Checklist test. His academic history of unremarkable; he had no history of problems with attention, learning or behavioral problems. He completed grade school with peers. He had graduated Warrant Officer Training (pilot training) with no delays or difficulty, and he scored in the high-average range on the ASVAB (GT = 110). His family life was positive and he denied any significant marital stressors. He also denied legal or financial stressors.

The tests given to the subject were: (1) Victoria Symptom Validity Test (VSVT), (2) Wechsler Adult Intelligence Scale; Fourth Edition (WAIS-IV), Repeatable Battery for the Assessment of Neuropsychological Status (RBANS) (Form A), (3) Trail Making Test (TMT) A and B, (4) Grooved Pegboard (GP), (5) Controlled Oral Word Association Test (COWAT), (6) Continuous Performance Test, 2nd Edition (CPT-II) and the Personality Assessment Inventory (PAI).

The patient performed perfectly on the VSVT and his results were deemed an accurate representation of his cognitive abilities. His overall intellectual functioning fell in the average range (FSIQ = 108) which was consistent with his estimated premorbid intellectual functioning (based on ASVAB), but slightly lower than AF pilot norms. Verbal (VCI) and non-verbal abilities (PRI) were average to above average respectively. His Working Memory Index (WMI) fell in the high average range (114) though the subtest scores comprising the scale were quite disparate. Simple digit repetition (Forward Digit Span; i.e. simple, focused attention) was superior while more complex, WM performance (Digits Backwards and Sequence) were average (99th percentile versus 50th percentile respectively). Differences here are rare and occur in less than 5%of individuals from normative samples. Overall FSIQ was also somewhat pulled down by slow PS. As can be seen in Table 1, there were significant differences between his overall PS and other scores [Processing Speed Index (PSI) fell below 10 percentile while all other Index scores were above 70th percentile]. Differences such as these are rare in normative samples (< 5%).

Other neurocognitive functions of attention, memory, visuospatial/constructive abilities were within or above normal limits and considered unimpaired. However, there were other scores that were below expectations and consistent with slowed PS seen on intellectual testing. For example, although his score on the RBANS Attention Index was overall above average, the two subtest scores comprising the Index were highly discrepant (z score for Digit Span = +1.72 versus Coding +0.17). Although overall CPT-II performance was within normal limits (WNL) his overall Hit Rate speed (psychomotor speed) was well below average. While Trails B performance was average, Trails A was slightly below. Lastly, there appeared a consistent pattern of low to below average scores on several iterations of Word Fluency, both semantic and phonemic (Word Fluency, RBANS and COWAT tests). Performance on a test of motor speed and dexterity was average and above average for non-dominant and dominant hands respectively.

Overall interpretation and conclusions from data were that this patient was still experiencing some ill effects of mTBI. This decision was made based on his low PSI score from WAIS-IV testing, overall low PS performance throughout the evaluation, and slightly below average word fluency scores. He was not recommended to return to flying duty at the time, but was recommended to follow-up with repeat testing in 6 months. During this time he continued to work in his unit and see a variety of medical professionals to aide his recovery (occupational health and cognitive rehabilitation).

Six months from his initial evaluation, he was given a brief repeat evaluation which focused on his aforementioned weaknesses. Tests given were select subtests from the WAIS-IV (Coding, Symbol Search, and Cancellation), Coding from RBANS (Form B), TMT A and B, and the COWAT (CFL versus FAS). As can be seen in Table 1, there was marked improvement from Time 1 to Time 2. PSI from WAIS-IV went from 79 to 100, an improvement of over a full standard deviation. Due to concerns of practice effects, the optional Cancellation subtest was also given, in which the patient scored in the high average range. On the RBANS, his z score on Coding went from the average to above average range (Form B). Additionally, his performance on Trails A & B both improved by over a standard deviation. COWAT performance also improved consistent with other scores. These changes were considered greater than those expected by practice effects, regression to the mean, or by chance.

The patient was assessed to have made a full recovery at this point. He had performed well at work and denied ongoing symptoms. Even prior to his second evaluation, he passed all in-flight checklists and trainings. He was recommended for psychiatric waiver for any ill-effects of his mTBI and a reinstatement of his Flight Duty status was recommended.

Case number two was a male in his mid-twenties at the time of the evaluation. He was seeking aeromedical clearance to attend flight school with aspirations to become a helicopter pilot in the US Army. He had sustained a complicated mTBI several months prior thus initiating the evaluation. He had no complaints and considered himself fully recovered at the time of the evaluation.

Fourteen months ago while working at a hardware store he had an accident where he injured his finger while on a ladder. Due to the pain he jumped backwards, lost his footing and fell and hit is head on concrete floor. He lost consciousness for approximately 1-2 minutes (per his estimation, there were no witnesses) but he awoke aware of his finger injury, fall, and that he had hit his head. PTA was not reported. He was taken by ambulance to a local hospital where neuroimaging showed a small right subarachnoid hemorrhage around the perisylvian fissure. Due to the lack of resources at the hospital, he was flown to a larger hospital where he remained overnight for observation. Additional scans done the next morning revealed no further bleeding and the patient was sent home to recover. He reported headaches, neck and back pain for two weeks after the accident, and did not return to work during this time. After two weeks all pain resolved and the patient returned to work under the recommendation of his physician. He denied any problems retuning to work or continuing post-concussive symptoms. He did not pursue a Workman’s Compensation claim from the fall at the warehouse and had no associated stressors commonly linked with such claims.

The patient reported no other significant medical history. He did not drink alcohol or use tobacco. He denied any sleeping problems. He stated that other than his injury he enjoyed “excellent” physical health.

Other biopsychosocial information was unremarkable. The patient had no history of behavioral health treatment (to include high school or prior). He was married and in a supportive, stable relationship and he denied any significant psychosocial stressors that might impair his ability to function. At the time of the evaluation he had just completed a demanding Army training course and performed at the top of his class. He had a high school education with no formal post-secondary education. His incoming ASVAB scores were high average (GT = 114). Prior to Army training he worked a variety of odd-jobs including his work at the hardware store. He had no history of poor work performance/early termination from positions, no legal history, and no disciplinary action taken against him while in he was in Army training.

The tests given to the subject were: (1) VSVT, (2) WAIS-IV, (3) TMT A and B, (4) Category Test: Computer Version, (5) GP, (6) COWAT, (7) CPT-II, (8) Rey Complex Figure Test (RCFT), and (9) the PAI.

Results of testing indicated no significant cognitive problems. He performed near perfect on the VSVT, missing only one item on the ‘Hard’ items of the test, indicating at least adequate effort. Intellectually, he performed in the high average range (FSIQ = 119), generally consistent with his estimated premorbid abilities and also known pilot norms. There were no significant differences between his verbal and non-verbal scores, and both fell in the superior ranges. His PSI score was high average and not significantly different from VCI or PRI scores. Though his WMI score was average, it was both clinically and significantly different than VCI and PRI scores.

Other neurocognitive functions of attention, visuospatial/constructive and executive functioning abilities, memory, and motor-sensory functioning were within or above normal limits and considered unimpaired (Table 2). Though his word fluency performance was low average this was likely due to normal intrapersonal variability and considered an insignificant finding. Other aspects of executive functioning were entirely within or above average (Trails B, CT and ROCFT copy performance). Two subtests on the CPT-II did indicate some problems with sustained attention; however, overall performance with entirely WNL and sustained attention deficits were not observed at other point in testing (Category Test, overall management of vigilance throughout entire battery).

The patient was assessed to have made a full recovery at this point. He denied any ongoing symptoms since returning to work and had performed well. He also had completed Army training scoring at the top of his class (personal report was verified by training records). He was recommended for psychiatric waiver for any ill-effects of his complicated mTBI and a recommendation for Flight School was supported.

Case number three was a male in his late twenties at the time of the evaluation. He was employed by the US Army and served as a helicopter pilot. He was referred for an AM NP evaluation after sustaining a mTBI three months prior. He had no presenting concerns at the time of the evaluation and considered himself fully recovered.

The patient was injured when he was riding his motorcycle and after losing control was forced into a vacant lot. He hit a hidden object in the grass and was thrown from his motorcycle. He landed on his left side and struck his head (grassy field). He was wearing a helmet, but lost consciousness following the crash. He awoke in the ambulance while paramedics attended to his injuries. He does not know exactly how long he lost consciousness, but estimates it was between 15–30 minutes and PTA was not reported. He underwent head MRI and CT imaging while at the hospital and both came back negative. Other than a shoulder sprain and general muscle soreness, he denied other injuries and was released from the hospital the same day. He reported headaches and mild attention problems for days following the incident. However, a week after the crash, his symptoms subsided.

Two months after the accident he underwent NP testing by a non-AM trained provider (still trained NP) utilizing primarily a computerized battery of tests. Review of records indicated the provider concluded at the time that the patient’s cognitive functioning “is collectively intact”. The report of the referring provider also concluded that the patient “failed to show any significant deficits.” Although the assessment concluded his PS scores were mildly lower than expected, they were not indicative of cognitive impairment that would interfere with his level of functioning nor ability to pilot an aircraft (data not available for review). Other measures of cognitive functioning, such as reaction time, visuo-spatial processing, memory, and attention were WNL. Despite all this, because the evaluation was conducted by a non-AM trained provider, a new evaluation was needed from an AM-trained provider and thus the reason for the evaluation. With patient permission, provider was contacted to assure none of the tests used in the new evaluation were used in the prior.

Other biopsychosocial information for this subject were unremarkable. He had recovered well from the injuries listed above and had no complicating medical history. He rarely used alcohol, had no history of alcohol-related problems, and denied use since injury. He denied significant post-concussive symptoms such as vestibular problems, headaches, nausea, etc. He had no psychiatric history. Occupationally, he had no significant problems or history. He had positive relationships with his peers, and had no disciplinary action taken against him at any point in his career. Upon his return from his injury he also showed no functional problems at work. His academic history was unremarkable; he had no history of problems with attention, learning or behavioral problems. He completed grade school with peers. He had graduated Warrant Officer Training with no delays or difficulty, and scored in the above average range on the ASVAB (GT = 117). He denied marital, financial or legal problems.

Because testing had already been done by another provider, the subject was given a somewhat abbreviated battery with less emphasis on computerized administration. The tests given to the subject were the: (1) Test of Memory Malingering (TOMM), (2) WAIS-IV, (3) TMT A and B, (4) GP, (5) COWAT, (6) CPT-II, and (7) the RCFT.

Test results summarized: Effort on testing was adequate as the patient easily passed all trials of TOMM administration and results were considered an accurate representation of his cognitive abilities. His overall intellectual functioning performance fell in the superior range (FSIQ = 122) which was consistent with his estimated premorbid intellectual functioning (based on ASVAB) and also known pilot norms. Verbal (VCI) and non-verbal abilities (PRI) both fell in the superior range. His working memory scores were high average. His PS scores, despite falling in the average range, were both significantly and clinically lower than other his abilities and indicated PS was an identified weakness for the subject.

Other neurocognitive functions of attention, visuospatial/constructive and executive functioning abilities, memory, and motor-sensory functioning were within or above normal limits and considered unimpaired (Table 3). In agreement with intelligence testing, Trails A performance was lower than expected, though not to an extent to consider impaired.

The patient was assessed to have made a full recovery at this point. He denied any ongoing symptoms since returning to work and had performed well. Similar to Case 1, even prior to his evaluation he had passed all in-flight checklists and trainings (verified with Command). Additionally, he had been seen by another trained NP whose findings denied any ongoing cognitive symptoms (though in narrative form report did state lower-than-expected PS scores). He was recommended for psychiatric waiver for any ill-effects of his mTBI and a reinstatement of his Flight Duty status was recommended.

4.1 Case summaries

These cases present a series of individuals, who were rated, or were attempting to become rated, Aviation personnel (two pilots and one pilot training applicant) at the time of their head injuries. Following time from injury and rehabilitation, each individual presented for NP evaluation to be medically cleared of possible cognitive impairment. In agreement with current literature and understanding of recovery from mTBI, each case was assessed to have made full cognitive and functional recovery, though PS was noticeably slower to recover than other abilities in 2 of the 3 cases. On one case, an additional 6 months of recovery was needed before a return to Flight Duty status could be recommended.

4.2 Case conclusions and integration into research

Though each case recovered functionally and cognitively, an interesting finding was that PS recovery was delayed in some cases. This agrees with literature on recovery from mTBI that shows a similar pattern largely due shearing effects that concussive blows have on white matter tracts in the CNS (Morgan & Ricker, 2008). Though admittedly this does not add any new information to the field the cases presented demonstrate this pattern in individuals who had financial incentives to perform well. Previous research has been complicated by the involvement of medico-legal cases in defendants recovering from mTBI, but these cases show a similar finding in those incentivized to do well on testing. In addition, none of the patients reported cognitive complaints at the time of evaluation including slowed PS. This suggests just as individuals presenting for NP evaluation can be negatively biased if incentivized, perhaps individuals can also be positively biased if incentivized as well.

Weaknesses of this project begin with it not being empirical in nature. No definitive conclusions can be made solely from a series of presented cases, and many variables important to recovery were not standardized (example: time-since-injury). Therefore, caution should be exercised when interpreting results. Additionally, generalizability is also limited in that each presented case had only a single blow to the head as mTBI history. Caution should be exercised when making any inferences from these cases and applying it to individuals who have long histories of multiple TBIs, blast injuries, or injuries through different mechanisms other than a single mTBI.

Despite the above weaknesses, there are several strengths of this project. One strength is that many identified factors that are known to hinder post-mTBI recovery were ruled out. US Army pilots and rated Aviation personnel are only accepted for flight status after screening negative for a variety of negative physical and mental health conditions. This is important because it rules out pre-injury characteristics that are often over-represented in mTBI research that have negative outcomes on recovery (Luoto et al., 2013; Isokuottri et al., 2016). Although this can limit the generalizability of results, it does isolate the biological and anatomical mechanisms involved in brain injury, and rules out known confounding variables such as certain personality traits or psychiatric history. This allows for a more thorough examination of what is often referred to as “organic” aspects of injury versus those that are non-organic.

The main strength of this study, however, is analyzing the performance of individuals who are financially incentivized to perform well on cognitive testing when recovering from mTBI, which likely improves their level of motivation to recover. Although the variable of motivation to recover is complicated and contains many other variables than simple financial incentives this is the first known set of cases or study known to examine cognitive testing in individuals who are incentivized to perform well. The complex issue of recovery from mTBI will remain unsolved insofar as the research paradigms directed at solving the issue remain unilateral. At this time, there is ample research showing how incentives to underperform on cognitive testing may affect long-term recovery from mTBI, but little to no research on how incentives to perform well may influence test results, or more broadly, recovery altogether.

The potential to conduct research that is more empirical, sophisticated and with appropriate sample sizes in the area of incentivized motivation to recover from mTBI exists. In the US Department of Defense there are a variety of specialty-select positions where individuals must present themselves for evaluation to rule-out cognitive impairment following mTBI and are incentivized to perform well. Likewise, in the civilian sector, there are also a variety of analog situations where individuals present for NP evaluation that incentivized to perform well (i.e. flight evaluations for Federal Aviation Administration, child-custody evaluations). Such evaluations are important in that they evaluate for positions that typically come with added responsibilities, demands, and competencies, and are desired by those seeking evaluation. Additional internal motivators such as positive elements of self-identity and conceptualization are often present. Such positions can also come with financial compensation or other external benefits. Evaluations of this type serve at the other end of the spectrum in terms of motivators for those seeking evaluation after mTBI and are imperative to include in the research to obtain a full and complete picture of the long-term consequences of mTBI.