Incidence of Cerebral Vasospasm and Delayed Cerebral Ischemia Following Non‐Traumatic Aneurysmal Subarachnoid Hemorrhage

Abstract

BackgroundNon‐traumatic aneurysmal subarachnoid hemorrhage (aSAH), comprising ~ 3 percent of strokes, is one of the deadliest stroke subtypes with mortality reaching as high as 40 percent. This high rate of mortality is associated with delayed cerebral ischemia (DCI), likely due to cerebral vasospasm (CV). CV is characterized by progressive narrowing of cerebral arteries, diagnosed by neuroimaging, that occurs within 4–14 days of aSAH, and CV leads to DCI and infarction in ~ 25 percent of patients. While the etiology of CV remains unknown, autonomic nervous system dysfunction, specifically excessive sympathetic nervous system induced vasoconstriction, may play a role. The purpose of this study is to review clinical cases of aSAH from 2017–2019 from our local hospital and describe the frequency of aSAH, CV, and DCI for all cases.MethodsInstitutional review board approval was received from West Virginia University. We performed a retrospective chart review of all patients diagnosed with non‐traumatic aSAH from January 1, 2017 – October 1, 2019 (n= 156). The following variables were collected from the medical record: location of aneurysm, presence and location of SAH blood clot (Fisher grade), frequency and severity of CV‐diagnosed by angiography or transcranial doppler, frequency of DCI within 7 days of CV – diagnosed by CT or MRI. Frequencies of CV and DCI were compared between location of aneurysm. Other potentially confounding variables were also collected, including age, sex, cardiovascular risk factors, and treatment with an alpha‐1 antagonist at time of aSAH presentation. Statistical analysis was performed using IBM Statistics (Version 26). Frequencies were compared between groups using Fisher’s exact test, and correlations between variables were assessed by Spearman correlation. Binary logistic regression was used to identify factors that may predict incidence of CV. Statistical significance was determined at p < 0.05.ResultsaSAH occurred in the anterior circulation in 71 percent of cases – middle cerebral artery (MCA) (23%), anterior cerebral artery (ACA) (20%), anterior communicating artery (20%), and internal carotid artery (ICA) (8%). CV occurred in 36 percent of all cases ‐ MCA (60%), ACA (26%) and ICA (12%). Hypertension was the only significant predictor associated with a higher incidence of CV (p=.032). Interestingly, the actual incidence of CV was not correlated with the expected incidence of CV predicted by Fisher grade (p=.656). CV led to DCI in 31 percent of cases, and there were no differences in DCI incidence compared between Fisher grade or vessel affected by CV.ConclusionsOur preliminary data provides a description of the incidence of CV and DCI following non‐traumatic aSAH at our institution. The observed incidence of CV and DCI are comparable to previously reported estimates; however, our results suggest that Fisher grade alone may not provide an accurate prediction for the incidence of CV, as the incidence of CV may vary across the cerebrovasculature. This study provides evocative evidence for further investigation into the factors that may contribute to CV and subsequent DCI. Upon validation, this information may be used by clinicians in the diagnosis and medical management of CV to prevent DCI and subsequently lower mortality associated with aSAH.