The Impact of Time-to-Intervention on Mortality and Functional Outcome in Acute Subdural Hematoma: A Systematic...

Introduction: Acute subdural hematoma (aSDH) represents one of the most lethal and debilitating forms of traumatic brain injury (TBI) encountered in neurosurgical emergency settings, carrying high mortality rates and severe long-term functional deficits. Historically, the timing of surgical decompression has been considered a critical modifiable prognostic factor. However, contemporary evidence regarding the relationship between time to surgery and clinical outcomes remains inconsistent. This systematic review and meta-analysis evaluates the impact of surgical timing on mortality and functional status in adult patients undergoing evacuation for acute subdural hematoma. Methods: A systematic review was conducted according to the PRISMA 2020 guidelines and registered in PROSPERO. A database search was performed across PubMed, Scopus, Embase and Web of Science for relevant studies published between 2009 and 2026. Peer-reviewed cohort studies and clinical trials including adults (>18 years) with CT- or MRI-confirmed aSDH were included. Data extraction focused on baseline characteristics, surgical timing thresholds, and primary outcomes of mortality and functional status assessed using the Glasgow Outcome Scale (GOS). Methodological quality was assessed using the Newcastle-Ottawa Scale. Relative risks (RR) and risk differences (RD) with 95% confidence intervals (CI) were calculated using a random-effects model. Results: The search identified 1815 records, of which six studies, including 926 patients, met the inclusion criteria. Meta-analysis found no statistically significant association between time to surgery and mortality (RR 1.01, 95% CI [0.69, 1.48], p = 0.96; RD -0.02, 95% CI [-0.19, 0.15]). High statistical heterogeneity was observed (I² = 80%) across the included cohorts. Most studies indicated that patients who underwent rapid neurosurgical intervention frequently presented with significantly worse baseline neurological status, which acts as a primary confounding factor and drives poorer prognostic trends. Conclusions: While historical paradigms emphasize a 4h period for subdural hematoma evacuation, our meta-analysis indicates that a straightforward linear relationship between time to intervention and improved survival or functional outcome is absent in contemporary clinical studies. Surgical timing thresholds must be interpreted cautiously, as the decision-making process is heavily guided by clinical triage bias, where rapidly deteriorating patients are prioritized for urgent decompression. Crude timing thresholds do not reflect a lack of causal benefit of early intervention but rather highlight the profound confounding by indication embedded in contemporary neurotrauma literature. Future multicenter investigations adjusting for admission severity, pupillary reactivity, associated intracranial pathology and other confounding factors are crucial to isolate the true prognostic value of surgical timing in aSDH.