Practical Pearl: Use of MRI to Differentiate Pseudo-subarachnoid Hemorrhage from True Subarachnoid Hemorrhage

Blood contains paramagnetic substances that alter the homogeneity of the magnetic field, so the presence of blood products such as deoxyhemoglobin leads to low signal intensity on GRE [6]. On presentation, the patient had a fever to 38.9 °C, heart rate of 106 beats per minute, and systolic blood pressure of 207 mmHg, and his Glasgow Coma Scale was 10 (E4V2M4). A follow-up CT scan (CT-3) after external ventriculostomy drain (EVD) placement demonstrated significant interval increase in diffuse hyperdensity in all cisterns and sulci, interpreted as worsening SAH versus possible pSAH (Fig. 1c). See PDF.] Absence of hemorrhage and resolution of hyperdensities. a Gradient recalled echo (GRE) images of the brain show no appreciable blood products in cisternal and sulcal spaces despite appearance of diffuse hyperdensity on previous CT scan. b FLAIR images of the brain demonstrating subtle increased signal within the CSF spaces, consistent with high protein content secondary to blood brain barrier breakdown and significant inflammatory response.