Dural sinus occlusion due to calvarial metastases: A CT blind spot.

Dural sinus thrombosis can be a difficult diagnosis to establish because it may present with nonspecific signs of raised intracranial pressure. Diagnosis by CT is well documented but signs may be subtle. Angiography is the "gold standard" but is invasive and requires a very high index of clinical suspicion to request. Magnetic resonance offers a method of demonstrating the dural sinuses in multiple planes and, furthermore, flow within the sinuses may be depicted by MR angiography. We report on three cases where the diagnosis of superior sagittal sinus thrombosis due to calvarial metastases was missed by CT, primarily due to their site over the convexity, but was demonstrated accurately using MR with MR angiography.