External validation of the modified Brain Injury Guidelines: an observational study

Background: Mild traumatic brain injury (mTBI) is a frequent cause of emergency department (ED) admission, with most cases being uncomplicated. However, a subset of patients presents with intracranial findings on CT, such as cerebral hemorrhage or skull fracture, that raise concerns for potential clinical deterioration. The modified Brain Injury Guidelines (mBIG) provide a risk-stratification framework for managing such patients but do not address cerebral hygromas or indeterminate radiological lesions, both commonly encountered in clinical practice. This study aimed to externally validate the mBIG criteria, including patients with cerebral hygromas and indeterminate radiological lesions on CT scan, in order to assess their prognostic accuracy for severe neurological outcomes. Methods: We conducted a retrospective single-center observational study of 451 adult patients presenting to the ED with a blunt head trauma who underwent initial CT imaging and clinical evaluation. Patients were classified as mBIG 1, 2, or 3 based on CT findings and clinical criteria. Outcomes were extracted from electronic medical records, with the primary outcome defined as a composite of death due to mTBI, neurosurgical intervention, or admission to intensive care unit. Results: Among 237 patients classified as mBIG 1, 38.8% exhibited an indeterminate radiological lesion and 35% had cerebral hygromas. The primary outcome was observed in only one mBIG 1 patient (0.4%; 95% CI: 0.0%–2.3%), demonstrating high sensitivity (94.7%; 95% CI: 74%-99.9%) and low negative likelihood ratio (0.1; 95% CI: 0.01-0.65), albeit with wide confidence intervals due to limited sample size. Radiological progression occurred in 6.3% of mBIG 1 patients, though none required neurosurgical intervention or intensive care admission Conclusion: The mBIG criteria appear to be a safe and efficient approach for managing complicated mTBI, even in cases involving cerebral hygromas and indeterminate radiological lesions. This preliminary validation suggests good prognostic performance, but further large-scale prospective studies are needed to confirm applicability in routine ED practice.