Appearance and disappearance of empty delta sign in superior sagittal sinus thrombosis.

The diagnostic value of the empty delta sign on post-infusion CT films was investigated in five patients with superior sagittal sinus thrombosis subsequently verified angiographically and/or pathologically. The empty delta sign, which has been considered to be unique and reliable in the diagnosis of cerebral venous sinus occlusion, was observed only on CT films taken one to four weeks after onset, and was not seen in the extremes of the acute or the chronic stage of the illness. These observations may explain why this sign has not been apparent in some reports concerning the CT findings of superior sagittal sinus thrombosis. Recanalization within the thrombus may be the reason why this sign was no longer apparent in the chronic stage of the patients with superior sagittal sinus thrombosis.