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Introduction: Subarachnoid hemorrhage (SAH) is a medical emergency that may lead to deleterious outcomes unless the underlying cause is determined and managed promptly to prevent further rebleed. Though a significant percentage of cases of SAH have no identifiable pathology, there is a lack of data related to outcomes, predispositions, and whether there has been an increase in the incidence of angiogram negative SAH (anSAH). This study aimed to assess the current incidence of anSAH and factors that are associated with outcomes and predisposition among patients diagnosed with anSAH.

Methods: A retrospective chart review was performed. Medical records of patients at Jefferson Hospital for Neuroscience who underwent cerebral angiography between 2010 and 2019 were reviewed to create a database from which patients diagnosed with anSAH were identified. Data related to clinical outcome, medical history, and demographics were collected. When data collection is complete, statistical analysis will be performed to evaluate the significance of the data.

Results: Of 4914 patients in the database, 1038 patients were identified as likely having anSAH, though the results must be verified. The incidence of anSAH was 21.1%. Due to ongoing data collection, no interim analysis was possible to assess variables associated with outcomes and predisposition for anSAH.

Discussion: As a result of incomplete data, the impact of the study on predicting outcomes and assessing predisposition for anSAH is unknown. However, the data suggest increased anSAH incidence in recent times, indicating that anSAH remains a significant subtype of SAH that clinicians should consider in the differential diagnosis.