[Intracranial aneurysms. A comparison between magnetic resonance tomography and arteriography]

42 MRI of 36 patients with cerebral aneurysms were analysed retrospectively and compared with selective angiography. 92% of aneurysms proven by angiography were also detected by MRI. The smallest and surgically confirmed aneurysms had a diameter of 2-3 mm on MRI. 3 aneurysms were only demonstrated by selective angiography (8%). This concerned 5 mm sized aneurysms located at the anterior communicating artery (2) and middle cerebral artery (1). On the other hand 2 thrombosed aneurysms were only delineated by MRI (6%). Because partial thrombosis could not be demonstrated by angiography extensions of aneurysms were underestimated in 44% (n = 16) angiographically. A 2.5 cm sized lobulated aneurysm of the internal carotid artery was initially evaluated by MRI as being thrombosed subtotally, due to flow-phenomena. Angiography though showed a wide perfused lumen without visible thrombosis. A progressive thrombosis of a mycotic aneurysm of the internal carotid artery was shown by MRI during septic thrombosis of the cavernous sinus. In this case the number of angiographic controls could be reduced by use of MRI. Nevertheless, MRI was not able to substitute selective angiography, especially to exclude under 6 mm sized cerebral aneurysms. MRI could not demonstrate clearly the vessels in the neighbourhood of saccular aneurysms preoperatively.