Postoperative Chronic Subdural Hematoma Following Unruptured Cerebral Aneurysm Surgery

Objective: We aimed to clarify the risk factors for postoperative chronic subdural hematoma (CSDH) following clipping surgery of unruptured cerebral aneurysms at our institute, where endovascular embolization is the treatment of choice for cerebral aneurysms. Methods: We reviewed the medical records of 20 patients who underwent clipping surgery for unruptured cerebral aneurysms between January 2010 and April 2014 at our hospital. The relationships between postoperative CSDH and age, sex, location of aneurysm, preoperative Evans index, and the amount of subdural fluid collection at postoperative days 6-14 were analyzed using analysis of variance and logistic analysis. Results: Nine of 20 patients (45%) developed postoperative CSDH, and 1 patient (5%) required burr hole surgery for symptomatic CSDH. CSDH developed at 7-230 days (average, 55 days) after surgery. The amount of subdural fluid collection at postoperative days 6-14 was significantly higher in patients who developed CSDH than in those who did not (p=0.04). The subdural space cutoff value for CSDH development was 8.2 mm. The ratios of males and middle cerebral artery (MCA) aneurysms were higher in patients with CSDH development than in others, but the differences were not statistically significant. Other factors did not correlate with the occurrence of CSDH. Conclusion: Postoperative subdural fluid collection was found to be associated with the development of postoperative CSDH after unruptured cerebral aneurysm surgery. Since CSDH may develop more than 6 months after surgery, long-term follow-up of patients is required in cases with large postoperative subdural fluid collection.