Background: Subdural hematoma (SDH) is the most common form of traumatic intracranial hemorrhage. Surgical intervention occurs in a small percentage of patients and is associated with clinical and radiographic features. Orlando and colleagues derived a prediction tool (the Orlando Tool) consisting of maximum thickness of hematoma and the presence of acute-on-chronic (AOC) hematoma. This investigation attempted to externally validate the Orlando Tool.
Methods: We performed a retrospective chart review of consecutive patients age ≥ 16 with a Glasgow Coma Score (GCS) ≥ 13 and CT-documented isolated, traumatic SDH who presented to a university affiliated, urban, 100,000-annual-visit ED from 2009-2015. The primary outcome of this investigation was neurosurgical intervention. Thickness of hematoma and presence of AOC hematoma were abstracted from cranial CT scan reports by two trained physician abstractors who were blinded to patient outcomes during abstraction. Discrepancies were resolved by investigator consensus.
Results: 619 patients with isolated SDH were reviewed and included in the validation dataset. Median hematoma thickness was 6mm. AOC hematoma was noted in 12.6% of patients. Mortality was 2.4%; 15.8% of patients underwent neurosurgery. The Orlando Tool had an AUC of 0.92 in the validation, comparable to 0.94 reported in the derivation. At the pre-specified cutoff of 9.96% risk, the rule had a sensitivity of 95% (95%CI 88-98) in the validation cohort, compared to 94% in the derivation. Specificity was 74% (95%CI 70-78), compared to 84% in derivation. Negative likelihood ratio was 0.07 (95%CI 0.03-0.16), compared to 0.09 in derivation.
Conclusion: An externally validated prediction tool can accurately identify a group of patients with isolated, traumatic SDH and preserved consciousness who will not need surgical intervention. While this is only one of a range of important outcomes, decisions support systems that can identify patients who are unlikely to need intervention have the potential to reduce unnecessary interfacility transfers, hospitalizations and imaging.