The cashew nut sign is a radiological sign described in juxtacortical intracerebral hemorrhages due to cerebral venous thrombosis, typically on CT.

The sign describes a small (<20 mm), concave-shaped intracerebral hemorrhage in the juxtacortical white matter, often near the bottom of a cortical sulcus, which resembles a cashew nut ^1-3. Presence of juxtacortical intracerebral hemorrhages has been found to be very specific (98%) for intracerebral hemorrhage due to cerebral venous thrombosis, typically of the superior sagittal sinus, but not very sensitive (26%) ^1,2.

It is thought that this unique cashew nut shape and juxtacortical location of hemorrhage is due to involvement of arcuate segments of the subcortical veins, which run parallel to subcortical U-fibers ^2,3. These subcortical veins drain into cortical veins and then venous sinuses and thus are affected by cerebral venous thrombosis ^2,3.