Hypodense cerebral venous sinus thrombosis on unenhanced CT: Time-dependent change of CT attenuation in intravenous thrombus

Cerebral venous sinus thrombosis (CVST) is an important cause of stroke, which accounts for 0.5%-1% of all strokes. CVST is principally manifested as headaches, papilledema, psychiatric symptoms, impaired consciousness and seizure disorders, with or without neurological defects. We encountered a case of CVST after subacute phase, revealing a hypodense thrombus in the superior sagittal sinus (SSS) on unenhanced CT. Retrospective observation of the serial unenhanced CT images taken at another hospital showed that the SSS thrombus changed from high to low attenuation for 10 days. RBCs dominant CVST at acute phase shows high attenuation on unenhanced CT and is effective for heparin therapy, whereas CVST after subacute phase shows low attenuation on unenhanced CT by the thrombus contents of fibrin, hemosiderin and collagen, and may be ineffective to heparin therapy. Therefore, it is important to accurately identify high attenuation of the CVST at acute phase on unenhanced CT and treat with heparin as early as possible.