Authors: Jai Deep Thakur, MD; Amey Savardekar; Stephenie Taylor; Nimer Adeeb; Devon Lefever; Matthew Hefner; Jared Brougham; Racheal Wolfson; Edward Burkhardt; Hai Sun; Bharat Guthikonda (Shreveport, LA)

Introduction: There has been a surge in the number of Nationwide Inpatient Sample (NIS) database studies. These studies have attracted publication in high impact journals. There is a discrepancy in the outcome endpoints of these studies in relation to the actual disease pathology. Objective of our study was to critically assess the viability of these studies in relation to Cerebral Aneurysms and provide relative reliability and extrapolation to neurosurgical patient population. Methods: We conducted a literature search from Jan 1995 to December 2017 using a standard PRISM criteria and databases including Pubmed, Google Scholar, EMBASE, and Cochrane. After screening, thirty-one studies were selected for critical analysis. Critical appraisal chart was formulated using modification of RECORD, STROBE and JAMA-Surgery Checklist. Results: Aneurysmal sub-arachnoid hemorrhage outcomes have been reported and compared across different treatment groups without controlling for WFNS/Fisher Grade, vasospasm, IVH, aneurysm location/size/morphology in all the studies reporting ‘outcome’. Ultra-early interventional studies are misleading in the setting of aneurysmal rupture which don’t control for transfer status (only available for 2 years in NIS database). External validation points for assessing the outcomes cannot compare to what the model of standardized randomized or prospective studies have provided so far. Missing data analysis is a statistical tool which again represents extreme heterogeneity in the data analysis for its valid extrapolation to the neurosurgical population. 74 % of the studies were published in high impact factor neurosurgery journals (Impact Factor >3). The mean lag between the year of publication and the years studied was 7.5 years (90 months). Conclusion: NIS database studies looking at Cerebral Aneurysms typically lag behind 7.5 years. Majority of the studies were published in top two neurosurgical journals. Lack of significant external validation and significant heterogeneity in the missing data analysis raises serious questions in universal extrapolation of these studies.