Flow artifact in the anterior communicating artery resembling aneurysm on the time of flight MR angiogram

Background: Magnetic resonance angiogram (MRA) of the brain is a widely employed non-invasive test to diagnose aneurysms. However, its overall accuracy is less than digital subtraction angiography and is prone to give false-positive or false-negative results. False-negative results can be seen with hemorrhage, lipoma, dermoid, posterior lobe of the pituitary gland, and the flow artifacts. Purpose: To describe the findings associated with false aneurysms in the anterior communicating artery on the time of flight MRA and review the physical principles behind this artifact. Material and Methods: This short series comprises of four patients whose MRA showed suspicious aneurysms in the region of the anterior communicating artery (ACOM) on time of flight MRA. Results: Two patients underwent catheter angiogram and the other two patients had computed tomography angiogram. None of these cases proved to have aneurysms and normal anterior communicating arteries were seen in all the patients. The findings on the MR angiograms were considered artifacts. All of the pseudoaneurysm had tapered appearance. Conclusion: MR angiogram can result in artifacts at ACOM which may be mistaken for aneurysm. Such pseudoaneurysms have characteristic appearance and should be followed up with non-invasive tests.