Supplementary Material for: Trends in Literature on Cerebral Bypass Surgery: A Systematic Review

Introduction: Ever since the beginning of cerebral bypass surgery, the role of the bypass has been debated and indications have changed over the last 5 decades. This systematic literature research analysed all clinical studies on cerebral bypass that have been published from January 1959 to January 2020 for their year of publication, country of origin, citation index, role of and indication for bypass, bypass technique, revascularized territory, flow capacity, and title (for word cloud analysis per decade). Methods: A systematic literature research was conducted using PubMed, Web of Science, EMBASE, and SCOPUS databases. All studies that have been published until January 1, 2020, were included. Results: Of 6,013 identified studies, 2,585 were included in the analysis. Of these, n = 1,734 (67%) studies addressed flow-augmentation bypass and n = 701 (27%) addressed flow-preservation bypass. The most common indication reported for flow augmentation is moyamoya (n = 877, 51%), followed by atherosclerotic steno-occlusive disease (n = 753, 43%). For flow preservation, the most common indication is studies reporting on cerebral aneurysm surgery (n = 659, 94%). The increasing popularity of reporting on these bypass operations almost came to an end with the FDA approval of flow diverters for aneurysm treatment in 2011. Japan is the country with the most bypass studies (cumulatively published 933 articles), followed by the USA (630 articles) and China (232 articles). Discussion/Conclusion: Clinical studies on cerebral bypass surgery have become increasingly popular in the past decades. Since the introduction of moyamoya as a distinct pathologic entity, Asian countries in particular have a very active community regarding this disease, with an increasing number of articles published every year. Studies on bypass for chronic steno-occlusive disease peaked in the 1980s but have remained the main focus of bypass research, particularly in many European departments. The number of reports published on these bypass operations significantly decreased after the FDA approval of flow diverters for aneurysm treatment in 2011.

介绍：自脑血管旁路手术（cerebral bypass surgery）诞生以来，其手术作用始终存在争议，手术适应证也在过去50年间历经变迁。本系统文献研究对1959年1月至2020年1月发表的所有脑血管旁路手术相关临床研究进行了分析，涵盖的分析维度包括：发表年份、起源国家、引用指数、旁路手术的作用与适应证、旁路技术、血管重建区域、血流容量，以及研究标题（用于分十年开展词云分析）。
方法：本研究通过PubMed、Web of Science、EMBASE及SCOPUS四大数据库开展系统文献检索，纳入截至2020年1月1日发表的所有相关临床研究。
结果：本研究共检索到6013项相关研究，最终纳入2585项进行分析。其中，1734项（67%）聚焦血流增强型旁路手术，701项（27%）聚焦血流保留型旁路手术。血流增强型旁路手术最常见的适应证为烟雾病（moyamoya，n=877，占比51%），其次为动脉粥样硬化性狭窄闭塞性病变（n=753，占比43%）；而血流保留型旁路手术最常见的适应证为脑动脉瘤手术相关研究（n=659，占比94%）。此类旁路手术相关报道的热度攀升趋势，在2011年美国食品药品监督管理局（Food and Drug Administration, FDA）批准用于动脉瘤治疗的血流导向装置后几近终止。发表旁路手术相关研究最多的国家为日本（累计发表933篇），其次为美国（630篇）与中国（232篇）。
讨论与结论：近数十年来，脑血管旁路手术相关临床研究的关注度持续提升。自烟雾病作为独立病理实体被提出以来，亚洲国家在该病的相关研究领域尤为活跃，每年发表的论文数量逐年增长。针对慢性狭窄闭塞性病变的旁路手术研究在20世纪80年代达到峰值，但至今仍是旁路手术研究的核心方向，在欧洲诸多临床科室中尤为突出。2011年FDA批准血流导向装置用于动脉瘤治疗后，此类旁路手术的相关报道数量出现显著下滑。