For half a century, the medical world has classified traumatic brain injuries using essentially the same tool: the Glasgow Coma Scale, a bedside scoring system developed in 1974 that rates a patient’s eye opening, verbal responses, and motor function on a 15-point scale. A score of 13 to 15 is “mild,” 9 to 12 is “moderate,” and 3 to 8 is “severe.” That three-tier system has driven clinical decision-making, research design, insurance determinations, and — critically for this audience — workers’ compensation claims adjudication for decades.
That system is now being replaced. In May 2025, an international team of 94 experts from 14 countries, led by the National Institutes of Health and the National Institute of Neurological Disorders and Stroke, published a new classification framework in The Lancet Neurology. Called CBI-M, it represents the most significant change in how traumatic brain injuries are assessed and categorized since the Glasgow Coma Scale was introduced. Trauma centers nationwide are beginning to test it, and workers’ compensation professionals handling head injury claims need to understand what is coming.
The problem with the mild/moderate/severe classification is not that it is inaccurate — it is that it is incomplete. Within the “mild” TBI category alone, there is enormous variation. One patient might sustain a brief blow to the head with no loss of consciousness and a momentary gap in memory. Another patient in the same “mild” category might lose consciousness for 20 minutes and have a small brain bleed visible on imaging. Under the current system, both receive the same classification, the same label, and — too often — the same clinical follow-up, which for “mild” TBI frequently means discharge from the emergency department with minimal arrangements for ongoing care.
The new framework does not discard the Glasgow Coma Scale — it expands on it. CBI-M stands for Clinical, Biomarker, Imaging, and Modifier, representing four pillars of assessment that together provide a multidimensional picture of the injury rather than a single number.
The clinical pillar retains the Glasgow Coma Scale but uses each component score individually rather than collapsing them into a single sum. It also incorporates pupillary reactivity — whether the pupils respond normally to light — which is a significant predictor of outcomes that the traditional GCS sum score alone does not capture.
The biomarker pillar is entirely new to TBI classification. It incorporates blood-based measures that can detect the presence and extent of brain injury. The FDA approved the first blood test for brain injury in 2018, and the technology has advanced rapidly since. Specific proteins released when brain tissue is damaged — including glial fibrillary acidic protein (GFAP), ubiquitin C-terminal hydrolase L1 (UCH-L1), and S100 calcium-binding protein B (S100B) — can now be measured from a standard blood draw within hours of injury. Elevated levels indicate that brain injury has occurred, even when the patient’s clinical presentation appears mild and CT imaging looks normal.
The imaging pillar formalizes the role of brain imaging — CT and MRI — in characterizing the injury. Rather than simply asking whether a scan is “positive” or “negative,” the framework categorizes the specific types of pathology present, such as contusions, hemorrhages, or diffuse axonal injury, each of which carries different implications for recovery.
The modifier pillar accounts for individual factors that influence clinical presentation and outcome: the mechanism of injury, the patient’s age, preexisting medical conditions, prior head injuries, and psychosocial factors. These modifiers have always been relevant to prognosis, but the current classification system ignores them entirely.
Independent medical examinations will need to adapt. Medical evaluators who currently rely on the GCS classification to frame their opinions about injury severity and causation will need to engage with the new framework. The biomarker pillar deserves special attention because it introduces something the workers’ comp system has never had for traumatic brain injury: an objective, measurable indicator of injury that does not depend on patient self-reporting or clinical judgment. Brain injury has historically been one of the most difficult conditions to evaluate in the claims context precisely because it lacks the kind of objective evidence — an X-ray showing a fracture, an MRI showing a disc herniation — that other orthopedic injuries produce. Blood-based biomarkers change that equation.
This does not mean biomarker testing will resolve all disputes. Elevated protein levels indicate brain injury but do not, by themselves, predict the duration of symptoms or the degree of functional impairment. And the science is still maturing — reference ranges, timing windows for testing, and interpretation standards are all subjects of active research. But the direction is clear: TBI evaluation is moving from subjective to objective, and the workers’ comp system will need to keep pace.
The CBI-M framework is not yet in universal clinical use. The authors describe it as a framework that will require validation and refinement before full adoption. But it is being tested at trauma centers now, it was published in one of the world’s leading neurology journals, and it carries the imprimatur of the NIH. The trajectory is unmistakable.
For further reading, the CBI-M framework was published in The Lancet Neurology in May 2025: A New Characterisation of Acute Traumatic Brain Injury: The NIH-NINDS TBI Classification and Nomenclature Initiative. The NIH-NINDS also published an accessible summary: New Framework for Classifying Traumatic Brain Injury.