The cerebral intravascular enhancement sign is not specific: a contrast-enhanced MRI study.

The intravascular enhancement (IVE) sign, also known as the "arterial enhancement sign", is an abnormal finding in the brain on contrast-enhanced MRI studies. IVE has been described in arterial cerebrovascular disorders, most commonly in acute or subacute arterial ischemic infarcts. However, the specificity of this sign has not been established. We describe four patients with disorders other than arterial strokes in whom gadolinium-enhanced high-field (1.5 T) MRI suggested IVE. The conditions were herpes simplex viral encephalitis, idiopathic cerebellitis, pneumococcal meningitis, and superior sagittal sinus thrombosis with venous infarction. IVE in these cases may be due to multiple factors, including arterial, venous, perivascular, and leptomeningeal or sulcal contrast medium accumulation. Our observations suggest that arterial ischemia, previously described as the cardinal cause of IVE, probably does not explain all instances, and urge caution in interpreting this sign as a specific MRI manifestation of acute arterial infarction or ischemia.