ObjectiveThe epidural fluid collection (EFC) as a complication of cranioplasty is not well-described in the literature. This study aimed to identify the predictive factors for the development of EFC as a complication of cranioplasty, and its outcomes.MethodsFrom January 2004 to December 2012, 117 cranioplasty were performed in our institution. One-hundred-and-six of these patients were classified as either having EFC, or not having EFC. The two groups were compared to identify risk factors for EFC. Statistical significance was tested using the t-test and chi-square test, and a logistic regression analysis.ResultsOf the 117 patients undergoing cranioplasty, 59 (50.4%) suffered complications, and EFC occurred in 48 of the patients (41.0%). In the t-test and chi-test, risk factors for EFC were size of the skull defect (p=0.003) and postoperative air bubbles in the epidural space (p<0.001). In a logistic regression, the only statistically significant factor associated with development of EFC was the presence of postoperative air bubbles. The EFC disappeared or regressed over time in 30 of the 48 patients (62.5%), as shown by follow-up brain computed tomographic scan, but 17 patients (35.4%) required reoperation.ConclusionEFC after cranioplasty is predicted by postoperative air bubbles in the epidural space. Most EFC can be treated conservatively. However, reoperation is necessary to resolve about a third of the cases. During cranioplasty, special attention is required when the skull defect is large, since EFC is then more likely.