We report computed tomography (CT) features in a case of segmental thrombosis of the superior sagittal sinus. On the initial cranial CT scan, both frontal cortices showed focal areas of slightly increased attenuation. The lesions were isointense on magnetic resonance (MR) images no matter what pulse sequence was used, except on fluid-attenuated inversion recovery images, which showed curvilinear sulcal hyperintensity. On postcontrast T1-weighted images, curvilinearly enhancing structures were apparent in both frontal cortical sulci. No lesion appeared on follow-up CT or in MR images. We speculated that the areas of slightly increased attenuation in the cortices represented blood congestion in the cortical veins, venules and capillaries without serum leakage. Cranial CT images should be carefully interpreted to avoid overlooking subtle lesions.