Risk factors of delayed surgical evacuation for initially nonoperative acute subdural hematomas following mild head injury.

BACKGROUND: Although the majority of patients with minimal acute subdural hematomas (aSDHs) can be managed conservatively, some require delayed aSDH evacuation due to hematoma enlargement. This study was designed to determine the risk factors associated with delayed hematoma enlargement leading to surgery in patients with aSDHs who did not initially require surgical intervention. METHODS: From 2002 to 2012, 98 patients were treated for nonoperative aSDHs following mild head injury (Glasgow Coma Scale scores of 13-15). The outcome variables were radiographic evidence of SDH enlargement on serially obtained computed tomography (CT) images and later surgical evacuation. Univariate and multivariate analyses were applied to both the demographic and initial radiographic features to identify risk factors for SDH progression and surgery. RESULTS: Overall, 64 patients (65 %) revealed minimal SDH or spontaneous hematoma resolution (conservative group) with conservative management at their last follow-up CT scan. The remaining 34 patients (35 %) received delayed hematoma evacuation (delayed surgery group) a median of 17 days after the head trauma. There were no significant differences between the two groups for baseline characteristics, including age, injury type, degree of brain atrophy, prior history of antithrombotic drugs, and coagulopathy. The presence of cerebral contusions and subarachnoid hemorrhages was more common in the conservative group (p = 0.003 and p = 0.003, respectively). On multivariate analysis, hematoma volume (p = 0.01, odds ratio [OR] = 1.094, 95 % confidence interval [CI] = 1.021-1.173) and degree of midline shift (p = 0.01, OR = 1.433, 95 % CI = 1.088-1.888) on the initial CT scan were independently associated with delayed hematoma evacuation. CONCLUSIONS: A critical proportion of patients with minimal aSDHs occurring after mild head injury can progress over several weeks and require hematoma evacuation. Especially patients with a large initial SDH volume and accompanying midline shift require careful monitoring of hematoma progression.