Nonaneurysmal "Pseudo-Subarachnoid Hemorrhage" Computed Tomography Patterns: Challenges in an Acute Decision-Making Heuristics

Abstract

Background: Acute aneurysmal subarachnoid hemorrhage (SAH) is a medical and neurosurgical emergency from ruptured brain aneurysm. Aneurysmal SAH is identified on brain computed tomography (CT) as increased density of basal cisterns and subarachnoid spaces from acute blood products. Aneurysmal SAH-like pattern on CT appears as an optical illusion effect of hypodense brain parenchyma and/or hyperdense surrounding cerebral cisterns and blood vessels termed as "pseudo-subarachnoid hemorrhage" (pseudo-SAH).

Methods: We reviewed clinical, laboratory, and radiographic data of all SAH diagnoses between January 2013 and January 2018, and found subsets of nonaneurysmal SAH, originally suspected to be aneurysmal in origin. We performed a National Library of Medicine search methodology using terms "subarachnoid hemorrhage," "pseudo," and "non-aneurysmal subarachnoid hemorrhage" singly and in combination to understand the sensitivity, specificity, and precision of pseudo-SAH.

Results: Over 5 years, 230 SAH cases were referred to our tertiary academic center and only 7 (3%) met the definition of pseudo-SAH. Searching the National Library of Medicine using subarachnoid hemorrhage yielded 27,402 results. When subarachnoid hemorrhage and pseudo were combined, this yielded 70 results and sensitivity was 50% (n = 35). Similarly, search precision was relatively low (26%) as only 18 results fit the clinical description similar to the 7 cases discussed in our series.

Conclusions: Aneurysmal SAH pattern on CT is distinct from nonaneurysmal and pseudo-SAH patterns. The origin of pseudo-SAH terminology appears mostly tied to comatose cardiac arrest patients with diffuse dark brain Hounsfield units and cerebral edema, and is a potential imaging pitfall in acute medical decision-making.

Keywords: Pseudo-subarachnoid hemorrhage; aneurysm; brain hypoxia; cardiac arrest; cerebral edema; computed tomography; medical heuristics; subarachnoid hemorrhage.