For fifty years, traumatic brain injuries have been sorted into three boxes: mild, moderate, and severe, based largely on the Glasgow Coma Scale. That shorthand is now being retired by the field itself.
In 2022, the National Academies of Sciences, Engineering, and Medicine published Traumatic Brain Injury: A Roadmap for Accelerating Progress. Its first recommendation is that clinicians should move beyond the mild, moderate, and severe labels, use results from neuroimaging and blood-based biomarkers when available and clinically indicated, and update the classification as the person's condition evolves [].
In 2025, the NIH-NINDS TBI Classification and Nomenclature Initiative, involving dozens of the field's leading investigators, published a new framework in The Lancet Neurology. It is called CBI-M: Clinical, Biomarkers, Imaging, and Modifiers. Blood-based biomarkers are one of its four pillars [].
Clinical diagnostic criteria have moved the same direction. In 2023, the American Congress of Rehabilitation Medicine published new diagnostic criteria for mild TBI, developed by an expert panel and endorsed for use across civilian, military, and sport settings. Under those criteria, diagnosis is clinical and multi-domain: mechanism of injury, observable signs, acute symptoms, examination findings, and supportive laboratory results, including elevated blood biomarkers, all contribute [].
The direction of travel is consistent across all three documents. Brain injury assessment is becoming multidimensional and objective, and the tools described in this section are the ones those bodies name.
What this does not mean is equally important. None of these frameworks replaces clinical judgment, and none endorses any single test as sufficient on its own. The word mild in mild TBI describes the initial clinical presentation, not the outcome [].