Localization and Treatment of Unruptured Paraclinoid Aneurysms: A Proton Density MRI-based Study

OBJECTIVE The purpose of this study was to evaluate the usefulness of proton density magnetic resonance (PD MR) imaging for localization of paraclinoid internal carotid artery aneurysms. MATERIALS AND METHODS From April 2014 to April 2015, 76 unruptured paraclinoid aneurysms in 66 patients were evaluated using PD MR and angiography (CT/MR angiography or digital subtraction angiography). The locations (extradural, transdural, intradural) in relation to the distal dural ring (DDR) and projection (superior, inferior/posterior, medial, lateral) of the aneurysms were assessed and compared. RESULTS The most common location of paraclinoid aneurysms was extradural (n = 48, 63.2%), followed by intradural (n = 18, 23.7%), and transdural (n = 10, 13.2%). In the medial projection group (n = 49, 64.5%), 31 were extradural (63.3%), 5 were transdural (10.2%), and 13 were intradural (26.5%). In the inferior/posterior projection group (n = 19, 25.0%), there were 14 extradural (73.7%), 4 transdural (21.0%), and 1 intradural (5.3%). In the superior (n = 4, 5.3%)/lateral (n = 4, 5.3%) projection groups, there were 0/3 extradural (0/75.0%), 1/0 transdural (25.0/0%), and 3/1 intradural (75.0/25.0%). CONCLUSION PD MR showed sufficient contrast difference to distinguish paraclinoid aneurysms from surrounding dural structures.