Traumatic brain injuries are a significant global public health issue. In this article from RGA's ReFlections newsletter, Dr. Pramodh Nathaniel reviews concussions and their related clinical conditions, highlighting key considerations for insurers navigating this shifting landscape.
Traumatic brain injuries (TBI) are a significant global public health issue and a leading cause of disability. An estimated 69 million people worldwide experience TBI annually, with most cases occurring in low-to-middle-income countries, primarily due to motor vehicle accidents.1
The terminology and diagnostic criteria for TBI are complex, with no universally accepted definitions.2 For example, the ICD-10 criteria for post-concussion syndrome differ from those outlined in the DSM-5 (Diagnostic and Statistical Manual of Mental Disorders, 5th Edition). While these systems rely on symptoms to define conditions, chronic traumatic encephalopathy (CTE) remains distinct, requiring postmortem brain analysis for definitive diagnosis.
Traumatic brain injury (TBI): Concussive and non-concussive events where the head impacts or is subjected to acceleration/deceleration forces due to a direct or indirect force to the head or body, resulting in a disruption of brain function or in signs of brain damage.
The exact mechanisms behind concussive symptoms remain unclear. Research suggests that trauma stretches nerve cell membranes and fibers (axons), triggering a neurometabolic cascade that leads to neuroinflammation and potential injury or cell death.
A common misconception is that concussions require loss of consciousness, which occurs only in a minority of cases. While severe neurological symptoms like post-traumatic amnesia, disorientation, epilepsy, or paralysis can result, mild traumatic brain injuries often present subtler signs, such as headaches, difficulty concentrating, a sense of mental fog or pressure, fatigue, irritability, and drowsiness.
Concussion: TBI resulting from a head impact or acceleration/deceleration event and causing neurological symptoms. Also can be termed mild TBI (mTBI).
Sports evaluation tools, such as the SCAT6 (Sport Concussion Assessment Tool) designed for individuals aged 13 and older, are used within 72 hours of injury, while the SCOAT (Sport Concussion Office Assessment Tool) assesses symptoms after three days. These tools help identify non-specific symptoms, track recovery, and grade concussions as mild, moderate, or severe, depending on the classification system.15
Treatment focuses on managing symptoms through rest and avoiding further head impacts. However, early, light activity is often recommended over complete rest. Ensuring full symptom resolution before returning to high-risk activities is critical to avoid “second impact syndrome,” a rare but life-threatening condition.
When concussive symptoms persist for four weeks to three months, the condition is termed post-concussion syndrome (PCS) or persistent post-concussive symptoms (PPCS). These terms, used interchangeably, can arise from repetitive mild TBIs (rmTBI), as well as moderate or severe TBIs.
Post-concussion syndrome (PCS)/persistent post-concussive symptoms (PPCS): Persistence of a constellation of physical, cognitive, behavioral, and emotional symptoms that occur after TBI.
The development of PPCS likely involves a complex interplay of biological factors, such as diffuse axonal injury, neuroinflammation, and altered cerebral blood flow, alongside psychological, socio-demographic, and personality factors. Incidence rates vary widely across studies due to differing diagnostic criteria, and controversy persists over whether PCS can be fully attributed to mild TBI. Subjective symptoms, which include headaches, fatigue, and mood changes, are non-specific and may predate the injury, complicating definitive diagnosis. Studies have even observed similar symptoms in healthy populations, non-head trauma patients, and individuals with chronic pain.4,5,7
An estimated 15% of individuals with mTBI develop PPCS, although some studies suggest rates as high as 25%, depending on the criteria used.8,9
Managing PCS is particularly challenging due to the complexity of symptoms and limited evidence for some treatments. Current approaches include:
The Australian Sports Commission’s 2024 “Concussion and Brain Health” position statement highlights a physiotherapy-guided rehabilitation plan, focusing on five key areas – the autonomic system, cervical spine, vestibular function, vision, and cognition – to guide an athlete’s safe return to activity.13,14,15
The neuropathological hallmarks of chronic traumatic encephalopathy (CTE-NC) include hyperphosphorylated tau (pTau) protein and neurofibrillary tangles (NFTs) or pretangles in specific brain regions characteristic of the condition. These abnormalities cluster around small blood vessels in the cerebral cortex, leading to progressive and debilitating neurodegeneration.
While tau deposition is common in several neurodegenerative diseases, such as Alzheimer’s, and in normal aging, the pattern and distribution of tau and NFT pathology in CTE are distinct enough to be considered diagnostically definitive.
The mechanisms underlying CTE remain unclear, but repetitive mild traumatic brain injuries (rmTBI) are believed to cause abnormal phosphorylation of tau protein. This misfolded and cleaved protein aggregates into clumps, potentially promoting the accumulation of other aggregate-prone proteins. These pathological changes can be confirmed only through autopsy, as they are not detectable via imaging.
The pathological stages of CTE are illustrated below:
The term CTE-NC (neuropathological changes) refers specifically to the condition diagnosed postmortem. In contrast, traumatic encephalopathy syndrome (TES) describes the clinical signs and symptoms associated with CTE-NC in individuals who are still alive.
Both conditions share features such as impairments in higher executive functioning, including short-term memory loss, mood instability, depression, and difficulties with decision-making and multitasking. TES is also linked to later-life conditions such as dementia and Alzheimer’s disease, and movement disorders like Parkinson’s disease.16
The relationship between repetitive mild traumatic brain injuries (rmTBI) and chronic traumatic encephalopathy (CTE-NC) remains controversial, with ongoing debate over whether rmTBI causes CTE-NC or is correlated with it. CTE-NC is a condition that develops over decades, requiring evaluation of head trauma from the distant past. Each mTBI is typically brief, often ambiguous, and rarely quantified, making rigorous clinical studies difficult.12
Research on CTE-NC largely consists of case reports, retrospective studies, and post-mortem analyses, often with selection bias. Many diagnoses come from retired athletes who donated their brains to sports brain banks.
Environmental factors, such as substance use, genetic predisposition, mental health history, and education level, further complicate causation studies. A 2023 study of 636 cases from the Sydney Brain Bank confirmed a low prevalence of CTE-NC in the general population (0.8%), with only five cases identified -three involving a history of TBI and two without.12
The Concussion in Sport Group’s 2023 “Consensus Statement on Concussion in Sport” acknowledged the potential link between extensive repetitive head impacts, such as those experienced by some professional athletes, and the neuropathology of CTE-NC. This influential group’s concussion protocols are widely adopted across elite and community sports worldwide.17
With no specific test or biomarker available, concussion diagnosis and monitoring rely on identifying relevant symptoms and clinical signs.
However, advancements in biomarkers and imaging technologies offer promising new tools for diagnosing mild traumatic brain injuries.
Brain injuries can cause proteins to leak from damaged cells into cerebrospinal fluid (CSF) or cross the blood-brain barrier into the bloodstream, where they can be measured. This evolving area of research shows promise for diagnosing mTBI. Biomarkers in blood, CSF, saliva, and urine are under investigation to help distinguish concussions from non-concussive head injuries, differentiate mild from severe intracranial injuries, and identify individuals at risk for prolonged symptoms.
The schematic below illustrates biomarkers currently being studied for diagnosing concussion-related conditions.15,18,19
In February 2018, the US Food and Drug Administration (FDA) approved the first blood test for detecting intracranial injury following a mild traumatic brain injury. This test measures two proteins: ubiquitin C-terminal hydrolase-L1 (UCH-L1) and glial fibrillary acidic protein (GFAP), markers of neuronal and glial cell damage. Because each protein originates from different brain cell types, their combined measurement provides complementary insights into intracranial injury. The test was approved specifically for emergency care use in adults over 18 to reduce unnecessary CT scans in patients with mTBI. A negative result within 12 hours of injury is associated with the absence of acute intracranial lesions on CT imaging.
The test is used alongside clinical information, Glasgow Coma Scale (GCS) scores (13-15 for mTBI), and clinical imaging guidelines, such as the Canadian CT Head Rule.21,22
In April 2024, the FDA approved a portable version of the test that delivers lab-quality results within 15 minutes and can evaluate patients up to 24 hours after injury.24 The US Army has partnered with a manufacturer to deploy this proprietary TBI test in field settings, citing nearly 500,000 troops who experienced TBI during training or deployment from 2000 to 2023.25
While these advancements show promise, current biomarkers cannot determine when the brain has fully healed, making them insufficient for guiding return-to-work or return-to-sport decisions. Furthermore, the longer the delay between injury and testing, the less sensitive the results. Continued research into biomarkers holds significant potential for improving concussion diagnostics and care.
Conventional CT and MRI scans are not effective for evaluating mTBIs or concussions, as these injuries often fall below the detection threshold or are too mild for individuals to seek imaging. While useful for ruling out structural damage and bleeding, these methods lack the sensitivity needed to diagnose mTBIs. Even with normal CT results, individuals can experience persistent symptoms for months or years following an mTBI.
Over the past decade, significant advances in imaging technology have improved the ability to detect milder TBI damage. However, the high cost and limited availability of these advanced modalities, especially in low- and middle-income countries, pose barriers to widespread adoption.
The growing recognition of concussion-related conditions like chronic traumatic encephalopathy (CTE) and persistent post-concussion symptoms presents unique challenges for insurers. With evolving medical research and increasing legal and regulatory scrutiny, the industry must adapt to manage these risks effectively. From underwriting models to claims management and policy design, insurers face significant opportunities and responsibilities to address the long-term implications of concussions.
The challenge for insurers lies in identifying individuals at risk of long-term consequences from mild traumatic brain injuries (mTBIs) while distinguishing them from the majority who recover without complications. Predicting and assessing this risk remains complex, with current medical science offering limited tools to address the uncertainty.
Until advancements in medicine and science provide more definitive answers, insurers face a difficult balancing act: managing a complex clinical condition while mitigating financial exposure. To navigate this uncertainty, insurers must adapt underwriting practices, refine risk models, and ensure policies address emerging needs. Staying informed about the latest research and innovations is essential for building strategies that both support policyholders and maintain sustainability.
By addressing these challenges with a proactive and informed approach, insurers can better serve their policyholders while navigating the complexities of an ever-evolving healthcare landscape.
With thanks to Dr. John Mayhew for sharing his generous time and deep expertise on this topic.
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