Mild Traumatic Brain Injury Update: Forensic Neuropsychiatric Implications

Methodological Deficits and Research Recommendations

Despite nearly an additional decade of time and a substantial upswing in public interest and funded research, the body of literature reporting on mTBI and its prognosis has demonstrated very modest progress. In 2014, Kristman et al.¹² reported that only 34 percent of eligible studies met criteria for ICMTBIP inclusion, a small increase over the 28 percent accepted by the WHO task force in 2002. “Despite the proliferation of mTBI research over the past decade, virtually no improvement was seen in study quality. These low acceptance rates indicate a literature plagued with poorly designed studies and as a result, many unanswered important clinical and research questions” (Ref. 12, p S266). In addition to problems surrounding risk of bias (i.e., lack of control of confounding factors, information bias, and selection and attrition bias), study design (i.e., lack of true comparison groups and use of small samples), unclear reporting regarding methods and results, inappropriate data analysis techniques, and methodological shortcomings, the literature also continues to feature a lack of uniformity in the definitions used to describe mTBI.

Clearly, there remain significant problems regarding study and publication quality in the mTBI literature. This circumstance has important implications for clinical care and medicolegal matters. Needless to say, clinicians may erroneously draw conclusions from peer-reviewed literature, wrongly assuming that definitions are accurate and methodologies suitable to the study's objectives. Take for example a recent publication featured in JAMA Neurology entitled “Imaging Correlates of Memory and Concussion History in Retired National Football League Athletes.” The authors report that “prior concussion that results in loss of consciousness is a risk factor for increased hippocampal atrophy and the development of mild cognitive impairment (MCI)” (Ref. 22, p 773). Readers might assume (or retained experts might claim) that this is a study of mTBI, and that it is applicable to patients who have sustained such an injury. Review of the Methods, however, reveals some problematic nomenclature; concussion, for example, is not used in a fashion consistent with accepted mTBI definitions: “Concussion severity ranged from brief periods of confusion to loss of consciousness for several hours” (Ref. 22, p 774).

In legal matters, one of the four criteria (under Daubert²³) used to determine the admissibility of scientific evidence includes the existence of peer-reviewed publications, but critical analysis of the peer-review process has caused some authors to make serious inquiries into its value.²⁴ Such concerns seem applicable to a body of literature that remains plagued by various methodological and reporting shortcomings. This very same body of literature is often co-opted by experts and attorneys in an effort to substantiate grossly atypical outcomes of concussive injuries. It is not uncommon to encounter situations where only certain articles in the TBI literature are referenced by medical experts to insinuate that a remarkably improbable neuropsychiatric presentation is compatible with the natural history of mTBI, with no meaningful reference to large-scale meta-analysis suggesting otherwise. Take the aforementioned example from the medical literature: it is not difficult to imagine how that publication, featured in a highly respected peer-reviewed journal, might be presented in support of claims that an mTBI has led to significant cognitive impairment or substantial risk of developing such. Literature reviews suggesting more grim prognoses and contained within medicolegal reports and running contrary to the available best medical evidence ought to be greeted with skepticism, with close attention paid to the individual publications cited and the methodological and reporting rigor surrounding those investigations.

The ICMTBIP also identifies a paucity of good data regarding litigation and compensation factors and how these may influence the outcome of mTBI. There is also no additional information available on compensation and litigation factors in mTBI recovery. Given the consistent evidence that litigation and compensation are associated with recovery after mTBI, further examination is needed to understand motivations behind this association and suggest policies that promote recovery (Ref. 12, p S276).

There does appear to be some relationship between litigation/compensation and atypical outcomes, and it seems likely that there are bidirectional components, meaning some atypical outcomes are driven by litigation/compensation, and some compensation/litigation is driven by atypical recoveries. In other words, some people remain symptomatic because they are suing, and some people sue because they are not getting better. Research exploring temporal relationships between injury event and transition to plaintiff status may shed light on such associations. A worthwhile investigation could involve testing the hypothesis that earlier legal engagement after an injury event that would typically be associated with full and fast recovery is associated with an increase in or maintenance of symptoms.

Cognitive, Psychiatric, and Mortality Outcomes of mTBI

The ICMTBIP presents findings based on 21 accepted studies and offers results generally in keeping with prior meta-analyses portending full and relatively fast recovery for most persons who sustain concussive injuries.¹³ In the first 48 hours to two weeks after injury, mTBI is consistently associated with cognitive deficits, although the nature and magnitude of identified neurocognitive deficits has varied across investigations. Recovery often occurs early, during the first month after injury, but results also suggest the potential for residual cognitive deficits, which may be associated with positive loss of consciousness. The ICMTBIP identifies limited evidence that complete recovery may take as long as six months or a year for some. There does not appear to have been any quality medical evidence to support long-standing severe neurocognitive impairment as a consequence of a single, uncomplicated mTBI. The ICMTBIP does report that “a limited number of exploratory studies suggest that certain cognitive deficits may last longer than 3 months in some populations, although there was no consistency on the exact deficits that were persistent. In some cases, the observed deficits were of questionable clinical importance” (Ref. 13, p S171). The ICMTBIP reports limited evidence that mTBI is a risk factor for affective disorders, psychotic disorders, and suicide, but cautions that such findings should be considered hypothesis-generating at this point. There was limited evidence that certain oculomotor and upper limb visuomotor functions may be affected negatively for up to one year after injury.

Three investigations offer evidence in support of the notion that expectations may influence outcomes from mTBI. “There were consistent findings that having negative expectations about head injuries is associated with poorer cognitive test performance” (Ref. 13, p S166). Such results lend support to the idea that iatrogenic injuries may result when patients or plaintiffs are directed toward evaluators with poorly informed opinions regarding mTBI and are offered discouraging prognostic predictions. Early transition from patient to patient–plaintiff status may foster such circumstances, blurring lines between clinical care and legal agendas, with needlessly grim predictions potentially morphing into self-fulfilling prophecies. Also notable are findings suggesting that health care visits occurring in the wake of mTBI may result in the identification of other, previously unknown health conditions. Of course, the discovery of such health conditions subsequent to mTBI does not establish a causal relationship with TBI, indicating the need for careful consideration before temporal relationships are accepted as evidence of injury. Overly reductionistic formulations risk missing other relevant conditions, yielding lost treatment opportunities and potentially perpetuating functional impairment.

Self-Reported Prognosis After mTBI

Although the best scientific evidence indicates a full and fast recovery for most persons who sustain uncomplicated mTBI, it is also well established that there remains a subset of individuals who experience persistent symptoms. Such atypical recovery probably occurs in roughly 10 percent of cases, and such outcomes are significantly influenced by factors unrelated to injury.^25,26 Recent findings by the ICMTBIP, described by Cassidy et al.,¹⁴ extend the body of evidence indicating that symptoms experienced subsequent to mTBI are nonspecific and very often relate to factors other than brain injury. Investigations comparing individuals with mTBI to persons with orthopedic injury “indicate that postconcussive symptoms, pain, and mental health are similar across acute injuries and not unique or specific to mTBI” (Ref. 14, p S134). Also noted are findings suggesting that patients with mTBI may misperceive their preinjury status, having a bias toward recalling it in an overly positive manner and a tendency to misattribute symptoms to injury. “The weight of this evidence suggests that postconcussion symptoms are nonspecific to mTBI, and clinicians should be cautious about attributing common postinjury symptoms to mTBI. This calls into question the validity of diagnosing postconcussion syndrome” (Ref. 14, pp S134–5). Results suggesting that expectations influence outcomes after mTBI are again identified.

Cassidy et al. report that: … most of the postconcussion symptoms could be viewed as common reactions to the stress of injury, or other mental or physical health stressors …. These symptoms are common in the general population, in patients with chronic pain, and after whiplash injury to the neck …. Thus, we recommend that the term postconcussion syndrome be replaced with posttraumatic symptoms because they are common to all injuries” (Ref. 14, p S149). Persistent symptoms are associated with a variety of psychosocial factors, including things such as depression, posttraumatic stress, negative injury perceptions, poor expectations for recovery, mental health status, anxiety, or litigation involvement. “In fact, the psychosocial factors are more strongly associated with outcomes than the traditional biomedical factors thought to determine recovery” (Ref. 14, p S149).

The best evidence indicates that although atypical recovery is a reality and that some individuals will go on to experience persistent symptoms subsequent to mTBI, such complaints may not be related at all to neuronal injury per se, but instead may result from a variety of non–brain-injury neuropsychiatric and psychosocial factors. Hence, atypical recoveries mandate a search for alternative explanations for persisting symptoms in terms of both competent clinical practice and objective medicolegal analysis. Arguably, the more dramatically atypical an mTBI outcome is, the more likely that alternative explanations exist and account for a substantial burden of impairment. Although the best clinical evidence may allow for some persistent symptoms directly stemming from neuronal injury in rare instances, there is a remarkable paucity of medical evidence to support the contention that neuropsychiatric impairment yielding severe functional disability (i.e., permanent inability to work and inability to live independently) results from a single, uncomplicated mTBI. The question of return to work after mTBI is specifically addressed in an ICMTBIP report by Cancelliere et al.¹⁸ They noted a very modest number of methodologically sound investigations, but they concluded that the best medical evidence indicates that mTBI does not appear to be a significant risk factor for long-term work disability.

For the most part, the previously described data regarding outcomes from mTBI are extended to pediatric cases in the ICMTBIP report by Hung et al.¹⁵ However, the pediatric mTBI literature has a relative paucity of acceptable studies investigating prognosis. That said, the best medical evidence suggests that pediatric uncomplicated mTBI is typically associated with full and relatively fast recovery and that, as in adults, common postconcussive symptoms are nonspecific to mTBI.

Risk of Dementia, Chronic Cognitive Impairment, and Parkinson's Disease After mTBI

Concern surrounding the long-term implications of concussive injuries has become widespread, in part because of the dramatic media attention paid to sports-related injuries. Much of this surrounds the controversial topic of chronic traumatic encephalopathy (CTE). Godbolt et al.¹⁶ specifically note that there are no established clinical criteria for CTE and that the relationship between brain injury and dementia remains uncertain, especially in cases involving mTBI. Nevertheless, clinical encounters in the present authors' TBI clinics often feature inquiries and anxiety surrounding the long-term risk of dementia. Medicolegal cases involving mTBI sometimes feature claims of increased risk for dementing illness, damages predicated upon such outcomes, and allusions using the CTE literature in efforts to substantiate otherwise grossly atypical outcomes.

Godbolt et al. identified no evidence in support of increased risk of dementia following single or repetitive mTBI. They noted very limited methodologically sound investigations addressing this important topic. “Taken together, there is insufficient evidence to draw any conclusions about a potential risk of dementia after mTBI (either single or repetitive injury). Clinicians and policy makers should be cautious about attempting to address this issue until more evidence is available” (Ref. 16, p S253). They identify objective evidence for chronic cognitive impairment at 12 months after injury only in pediatric cases of complicated mTBI. Once again, the potential for negative expectations to yield worse outcomes is noted. The ICMTBIP report by Marras et al.¹⁷ extends findings to Parkinson's disease, where once again the best available medical evidence argues against an important causal relationship with mTBI. In light of this body of work and the need to offer testimony within a reasonable degree of medical certainty or probability, expert opinions portending increased risk of neurodegenerative illness after concussive injury are not in keeping with the state of the science and the best available medical literature.