Concussions are a form of traumatic brain injury that typically result from a head impact. Also known as mild traumatic brain injuries or mTBIs, concussions present symptoms ranging from headaches and nausea to difficulties with memory or concentration. Because the physical signs are limited or challenging to quantify, they are difficult to accurately diagnose without patient input, leading to legitimacy questions in injury claims. To assess such claims, it is helpful to understand the current state of knowledge on concussions and assess the limitations of applying this knowledge towards the resolution of files.
There are currently many hypotheses on the injury mechanisms of a concussion, with the most recent research trends finding correlations with brain strain and pressures. From a biomechanical standpoint, estimating brain deformations requires intimate details of the accident that might be impractical for industry application. Instead, we must turn to the research that is working on a correlation between brain response and kinematic metrics, such as the impact accelerations and durations. The most extensive research done on this matter to date is a 2004 study where 24 football head impacts were experimentally reconstructed and studied (Zhang2004). The head kinematics were measured and the impacts were categorized depending on whether the athlete suffered a concussion or not. The head impacts were also reconstructed computationally to collect more detailed data so the study could evaluate head kinematics and brain tissue response.
The results and statistical methods used in this study allowed the authors to identify probability curves for several kinematic metrics, giving injury threshold probabilities. Much of this research has been corroborated with studies completed both before and after this 2004 study. Rotational acceleration, the acceleration that results from the head spinning about one of its axes, is another kinematic metric hypothesized to have a significant impact on the development of concussion symptoms. However, it has recently been suggested that a non-impact brain injury is improbable due to the biomechanics involved with transmitting enough energy through the human neck without the neck sustaining a significant injury. Also, statistical correlation studies of accident reconstructions have not found rotational acceleration to be significant compared to other kinematic metrics.
Although there is notable research being done to identify and evaluate injury metrics to determine the statistical “best” metrics for identifying injury prediction, there remains low predictive accuracy. As a result, there is debate among the medical and academic communities around the exact concussion injury mechanism and the validity of using these thresholds in practice. Furthermore, there are additional concussion risk factors that have not been quantified, such as the cumulative effect of multiple head impacts or the effect of a patient’s history of concussion. Psychological factors have also been observed to affect the expression and the duration of symptoms, as well as the development of persistent post-concussion syndrome.
With enough accurate information, CEP Forensic’s biomechanical engineers can conduct an accident reconstruction and a biomechanical evaluation to evaluate the kinematic metrics experienced by the head. This may be useful in determining whether and how a head impact occurred and how the kinematics relate to those found in academic literature on concussion. However, because the threshold limits of kinematic tolerance values are still so hotly debated, we can only deal in conservative likelihoods while considering other possible contributing factors in our opinions on concussion occurrence. The field of biomechanical engineering is a rapidly evolving field, and here at CEP Forensic, we are constantly monitoring the academic and medical developments on concussion research. By staying on top of the current research we will ensure your claims are resolved as accurately and scientifically possible.
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 L Zhang, K H Yang and A I King. “A proposed injury threshold for mild traumatic brain injury”. Journal of Biomechanical Engineering 126 (2004): pp. 226-236.