Pseudo-Subarachnoid Hemorrhage: A Potential Imaging Pitfall Chun-Yu Lin, MD, Ping-Hong Lai, MD, Jui-Hsun Fu, MD, Po-Chin Wang, MD, Huay-Ben Pan, MD  Canadian Association of Radiologists Journal  Volume 65, Issue 3, Pages 225-231 (August 2014) DOI: 10.1016/j.carj.2013.07.003 Copyright © 2014 Canadian Association of Radiologists Terms and Conditions

Figure 1 A 47-year-old man with hypoxic ischemic encephalopathy. (A, B) Precontrast computed tomography, showing uncal herniation, increased attenuation over basal cisterns and sylvian fissures, and tentorium (white arrows) and cerebrospinal fluid space (black arrows). Diffuse low attenuation over the bilateral hemisphere with poor grey-white matter differentiation is characteristic for hypoxic ischemic encephalopathy. Canadian Association of Radiologists Journal 2014 65, 225-231DOI: (10.1016/j.carj.2013.07.003) Copyright © 2014 Canadian Association of Radiologists Terms and Conditions

Figure 2 A 55-year-old man with tuberculous meningitis. (A) Precontrast computed tomography (CT), showing increased attenuation over basal cisterns (black arrows) and along the tentorium (white arrows). (B) Postcontrast CT, showing vivid enhancement in the same regions. Canadian Association of Radiologists Journal 2014 65, 225-231DOI: (10.1016/j.carj.2013.07.003) Copyright © 2014 Canadian Association of Radiologists Terms and Conditions

Figure 3 A 56-year-old man with a sudden onset of right-side weakness. (A) Precontrast computed tomography (CT), showing cerebrospinal fluid space narrowing with increased attenuation along basal cistern and sylvian fissures (black arrows) and tentorium (white arrows). (B, C) Precontrast CT, showing left-side anterior cerebral artery and middle cerebral artery infarction (star in each B and C). Canadian Association of Radiologists Journal 2014 65, 225-231DOI: (10.1016/j.carj.2013.07.003) Copyright © 2014 Canadian Association of Radiologists Terms and Conditions

Figure 4 A 54-year-old woman had recent dizziness and left-side weakness. Noncontrast computed tomography (CT), showing increased density along the tentorium (black arrow), with pronounced effacement of basal cistern (black star in [A]), mimic subarachnoid hemorrhage. (B) Large amount of mixed stage right-side subdural hematoma (white star), with obvious midline shift (white arrow) noted. Canadian Association of Radiologists Journal 2014 65, 225-231DOI: (10.1016/j.carj.2013.07.003) Copyright © 2014 Canadian Association of Radiologists Terms and Conditions

Figure 5 A 54-year-old woman with a seizure attack after transjugular intrahepatic portosystemic shunt. (A, B) Precontrast computed tomography (CT), showing bilateral, mutifoci ill defined and subtle high densities in the subarachnoid space and/or brain cortical regions (arrows) with brain swelling. (C, D) Her seizure subsided 3 days later. Precontrast CT, showing resolution of prior high-density lesions. Canadian Association of Radiologists Journal 2014 65, 225-231DOI: (10.1016/j.carj.2013.07.003) Copyright © 2014 Canadian Association of Radiologists Terms and Conditions

Figure 6 A 19-month-old boy had status epilepticus after the flu-like symptoms. (A-C) Precontrast computed tomography (CT), showing hyperdensity over the basal cisterns (black arrows) and along the tentorium (white arrows), with pronounced effacement of basilar cisterns. Diffuse low density over bilateral basal ganglia (white stars [C]), with diffuse brain swelling (black stars [B]) and uncal herniation, which suggests that this acute encephalopathy presumably was induced by viral infection and status epilepticus, probably associated with hypoxia. Canadian Association of Radiologists Journal 2014 65, 225-231DOI: (10.1016/j.carj.2013.07.003) Copyright © 2014 Canadian Association of Radiologists Terms and Conditions

Figure 7 A 35-year-old woman with spontaneous intracranial hypotension. (A, B) Precontrast computed tomography, showing tight basal cistern and increased attenuation along the basilar cisterns and sylvian fissures (black arrows) in addition to subdural hematoma (white arrowheads [A and B]). Canadian Association of Radiologists Journal 2014 65, 225-231DOI: (10.1016/j.carj.2013.07.003) Copyright © 2014 Canadian Association of Radiologists Terms and Conditions

Figure 8 A 55-year-old man with severe headache and vomiting after a myelography. (A, B) Precontrast computed tomography, showing increased density along cerebrospinal fluid space (arrows [A and B]). The patient got relief of symptoms 2 days later. Canadian Association of Radiologists Journal 2014 65, 225-231DOI: (10.1016/j.carj.2013.07.003) Copyright © 2014 Canadian Association of Radiologists Terms and Conditions

Figure 9 A 3-year-old man with secondary polycythemia (hematocrit level, 65%) due to congenital heart disease of transposition of the great vessels. (A) Precontrast computed tomography (CT), showing diffuse intravascular hyperdensity in the branches of the circle of Willis, along tentorium cerebelli and sigmoid sinuses. (B, C) Precontrast CT, showing diffuse hyperdensity in the deep veins, dural venous sinuses, and small vasculature of cerebral parenchyma. Canadian Association of Radiologists Journal 2014 65, 225-231DOI: (10.1016/j.carj.2013.07.003) Copyright © 2014 Canadian Association of Radiologists Terms and Conditions