Predictors of subacute hematoma expansion requiring surgical evacuation after initial conservative treatment in patients with acute subdural hematoma

Background The aim of this study was to clarify the factors associated with requiring subacute surgery in patients with acute subdural hematoma (ASDH) treated conservatively at admission. Methods Among the patients with ASDH admitted to our hospital from 2007 to 2018, we retrospectively reviewed data for 200 patients initially treated conservatively. We compared patients' characteristics, medical history, radiological findings, and clinical outcomes and differences between patients undergoing subacute surgery or no surgery. Results Of the 200 patients treated conservatively, 17 (8.5%) patients underwent subacute surgery due to deterioration of their clinical and/or computed tomography (CT) findings, while 183 (91.5%) patients did not undergo subacute surgery. There were significant differences in the presence of focal neurological deficits, modified Rankin Scale scores, degree of midline shift, hematoma thickness, hematoma volume, cella media index, Sylvian fissure ratio, and hematoma density between the two groups. Conclusions Large hematoma, brain atrophy, and hematoma density may be useful predictors for the need for subacute surgery in patients with ASDH treated conservatively at admission. Intensive investigation of clinical findings or CT images is warranted in patients with adverse prognostic factors, even if their initial symptoms are mild.