Many unruptured intracranial aneurysms may have a benign course, but carry a risk for rupture, with potentially catastrophic subarachnoid hemorrhage if intradural. Generally, extra-dural aneurysms are considered relatively benign, with rupture being probably less common, but most importantly usually not life threatening. As such it is important to accurately determine the size, morphology and location of cerebral aneurysms.

This is the exception to that rule, as rupture may well decompress into the sphenoid sinus resulting in life-threatening epistaxis. 

While CT and MRI are excellent tools to identify unruptured cerebral aneurysms, catheter angiography remains the gold standard, especially with 3D surface shaded reconstructions.