CLINICAL ARTICLE J Neurosurg 129:711–717, 2018 O verlapping surgery is defned as 2 operations being performed by the same primary attending surgeon simultaneously without any overlap of the critical or key portions of the operations. 2,3 Overlapping surgery is a controversial topic in medicine today, and the safety of this practice has been questioned in recent reports. 1,21 Con- cerns about patient safety have led to nationwide changes in surgical scheduling regulations; however, limited data examining this practice exist. No studies published to date have found any evidence of worse outcomes with overlap- ping surgery; 5,9,11,23 however, these studies examined het - erogeneous populations of patients undergoing a variety of neurosurgical procedures. It seems reasonable that, if a difference exists between overlapping and nonoverlapping surgical results, it would be most obvious in patients undergoing a highly complex surgical procedure, such as aneurysm clipping for acute subarachnoid hemorrhage (SAH). We therefore sought to ABBREVIATIONS BRAT = Barrow Ruptured Aneurysm Trial; GCS = Glasgow Coma Scale; GOS = Glasgow Outcome Scale; LOS = length of stay; MMSE = Mini–Mental State Examination; mRS = modified Rankin Scale; NIHSS = National Institutes of Health Stroke Scale; SAH = subarachnoid hemorrhage. SUBMITTED February 13, 2017. ACCEPTED May 8, 2017. INCLUDE WHEN CITING Published online November 3, 2017; DOI: 10.3171/2017.5.JNS17394. Analysis of overlapping surgery in patients undergoing microsurgical aneurysm clipping: acute and long-term outcomes from the Barrow Ruptured Aneurysm Trial Michael A. Mooney, MD, Scott Brigeman, MD, Michael A. Bohl, MD, Elias D. Simon, BA, John P. Sheehy, MD, Steve W. Chang, MD, and Robert F. Spetzler, MD Department of Neurosurgery, Barrow Neurological Institute, St. Joseph’s Hospital and Medical Center, Phoenix, Arizona OBJECTIVE Overlapping surgery is a controversial subject in medicine today; however, few studies have examined the outcomes of this practice. The authors analyzed outcomes of patients with acutely ruptured saccular aneurysms who were treated with microsurgical clipping in a prospectively collected database from the Barrow Ruptured Aneurysm Trial. Acute and long-term outcomes for overlapping versus nonoverlapping cases were compared. METHODS During the study period, 241 patients with ruptured saccular aneurysms underwent microsurgical clipping. Patients were separated into overlapping (n = 123) and nonoverlapping (n = 118) groups based on surgical start/stop times. Outcomes at discharge and at 6 months, 1 year, 3 years, and 6 years after surgery were analyzed. RESULTS Patient variables (e.g., age, smoking status, cardiovascular history, Hunt and Hess grade, Fisher grade, and aneurysm size) were similar between the 2 groups. Aneurysm locations were similar, with the exception of the overlap- ping group having more posterior circulation aneurysms (18/123 [15%]) than the nonoverlapping group (8/118 [7%]) (p = 0.0495). Confrmed aneurysm obliteration at discharge was signifcantly higher for the overlapping group (109/119 [91.6%]) than for the nonoverlapping group (95/116 [81.9%]) (p = 0.03). Hospital length of stay, discharge location, and proportions of patients with a modifed Rankin Scale (mRS) score > 2 at discharge and up to 6 years postoperatively were similar. The mean and median mRS, Glasgow Outcome Scale, Mini–Mental State Examination, National Institutes of Health Stroke Scale, and Barthel Index scores at all time points were not statistically different between the groups. CONCLUSIONS Compared with nonoverlapping surgery, overlapping surgery was not associated with worse outcomes for any variable at any time point, despite the complexity of the surgical management in this patient population. These fndings should be considered during the discussion of future guidelines on the practice of overlapping surgery. https://thejns.org/doi/abs/10.3171/2017.5.JNS17394 KEY WORDS microsurgery; outcomes; overlapping surgery; saccular aneurysms; subarachnoid hemorrhage; vascular disorders J Neurosurg Volume 129 • September 2018 711 ©AANS 2018, except where prohibited by US copyright law