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Bilateral Chronic Subdural Hematoma Presenting with Pseudo-Subarachnoid Hemorrhage Sign on Computed Tomography

Background: On rare occasions, cisterns are demonstrated as high-density areas on computed tomography (CT) and misdiagnosed with subarachnoid hemorrhage (SAH). This false-positive finding is called pseudo-SAH. Patients and Methods: From April 2014 to August 2018, a total of 161 patients with chronic subdural hematoma (CSDH) were treated in our hospital. For these cases, the existence of a pseudo-SAH sign on CT was retrospectively examined. Results: One patient with bilateral CSDH showed pseudo-SAH and a further examination to evaluate vascular abnormalities causing true SAH was necessary. In three patients, the Sylvian fissures were demonstrated as high-density areas due to an atherosclerotic middle cerebral artery; however, the condition was not misdiagnosed with SAH. Conclusion: In cases of CSDH, there is a possibility that CT demonstrates a pseudo-SAH sign. In such cases, close examinations to exclude true SAH are mandatory.