The pseudo-delta sign is unreliable in differentiating between aneurysmal SAH and sinus thrombosis in unenhanced brain CT

Pseudo-delta sign (PDS) represents spontaneous opacification of freshly-congealed blood within the subarachnoid space around the sinus, which shows up as a relative low attenuation structure in non-enhanced scans. With contrast injection, opacification of the collateral veins in the superior sagittal sinus wall is visible as a dense margin which contrasts with the un-opacified clot inside the sinus. Although subarachnoid hemorrhage (SAH) and superior sagittal sinus thrombosis (SSST) both share the PDS, the frequency of positivity of PDS was not different between the SAH and SSST cases. This suggests that it represents a non-specific sign, whose utility in differentiating between various neurological disorders is limited.