Delta sign and Reverse Delta sign

These are seen classically in SSS Thrombosis.

On noncontrast CT scan, the classic finding is the delta sign, which is observed as a dense triangle (from hyperdense thrombus) within the superior sagittal sinus. However, this is not specific, since high attenuation in the healthy nonthrombosed sinus can be observed occasionally and is common in neonates because of an elevated hematocrit.
On contrast-enhanced CT scan, the reverse delta sign (ie, empty triangle sign) can be observed in the superior sagittal sinus from enhancement of the dural leaves surrounding the comparatively less dense thrombosed sinus.
The presence of both the delta and reverse delta signs increases the likelihood of the diagnosis.
A false-positive delta sign may occur in a trauma setting because of an adjacent subdural hematoma.
The dural sinus normally may appear hyperdense relative to adjacent tissues. Both the delta and reverse delta signs may need to be present to establish the diagnosis.
Occasionally, the superior sagittal sinus may bifurcate proximal to the torcular herophili, resulting in a confluens sinuum and an empty delta sign without the presence of a venous thrombosis.