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Empty delta sign

Dr Frank Gaillard et al.

The empty delta sign is CT sign of dural venous sinus thrombosis of the superior sagittal sinus, where contrast outlines a triangular filling defect (clot). The exact mechanism for this appearance is uncertain, with possibilities including:

recanalisation around an organising clot
enlargement of the peri-dural small veins: a vascular mesh (dural cavernous spaces), and meningeal venous tributaries
thickening of the dura with increased enhancement