In older adults, “mild” by GCS does not mean low risk: Multicenter study of 1,157 patients with mild TBI and acute subdural hematoma

BACKGROUND: Acute traumatic subdural hematoma (SDH) is the most common intracranial injury in mild TBI (mTBI), particularly in older adults. However, the relationship of patient and brain computed tomography (CT) characteristics with outcomes remains poorly described in a contemporary cohort. This study aims to characterize outcomes in younger and older adults with mTBI and isolated acute SDH. METHODS: This was a 10-center, retrospective cohort study of adult traumas with emergency department Glasgow Coma Scale (GCS) 13 to 15 and acute traumatic SDH on initial brain CT ('22-'23). Trauma registry, EHR, and Picture Archiving and Communication System (PACS) data were collected through automated and manual methods. The primary outcome was total mortality (TM=death+hospice discharge); the sample was stratified by 18 to 64 versus older than or equal to 65 years. Multivariable backward selection logistic regression examined 21 demographic, injury, and brain CT covariates. RESULTS: In total, 1,157 patients were included (18-64 y: 28%; ≥65 y: 72%; 58% transferred in). Median [IQR] non-head ISS was 1 [1-5] in 18 to 64 years, and 1 [1-2] in older than or equal to 65 years. Ten percent had neurosurgical intervention (18-64 y: 8%; ≥65 y: 11%). TM was higher in older than or equal to 65 years than 18 to 64 years (10% vs. 3%). Compared with older than or equal to 65 years, 18 to 64 years were discharged home more frequently (78% vs. 51%) and to hospice less frequently (2% vs. 7%). In 18 to 64 years, factors associated with TM were race, advance directive, functional dependence, ISS, more midline shift, and thicker SDH (too few TMs for adjusted models). In older than or equal to 65 years, factors independently associated with TM were advance directive (aOR [95% CI]: 11.8 [2.9-49.0]), male sex (3.0 [1.3-7.0]), midline shift (1.8 [1.3-2.6]), shock index (1.5 [1.1-2.1]), and worsening SDH on follow-up CT (2.9 [1.3-6.6]). CONCLUSIONS: Despite presenting as "mild", these data highlight that older adults with SDH have high TM and should continue to receive the highest-level care with timely goals-of-care discussions. The association between advance directives and TM should be interpreted within the context of baseline vulnerability and preinjury treatment preferences, not as a biological mortality predictor. LEVEL OF EVIDENCE: Level III, prognostic/epidemiological.