Angiographic Morphological Characteristics of Middle Cerebral Artery aneurysms

Background: The treatment of Middle Cerebral Artery Aneurysms (MCAA) and the relation of their morphology to the chance of  rupture are an important topic in vascular neurosurgery. Objective: To assess the correlation between MCAA morphology and 1) the chance of aneurysm rupture and 2) its morbimortality. Methods: Twenty-nine patients with MCAA at the M1 segment (4 patients had multiple aneurysms), were followed/ treated by our crew at a single institution over the last 5 years; 14 aneurysms were ruptured at the time of admission and 15 were diagnosed incidentally. Aneurysms were classified by shape and their geometries were correlated with rupture rate and their morbimortality. Results: Aneurysms measured between 7 and 10 mm in diameter (90% of the aneurysms), and there was no difference in size between the ruptured and unruptured aneurysms. Patients whose MCAAs were ruptured at admission were 3 times as likely than patients with unruptured aneurysms to have a transverse elliptic or inverted-pear-shaped aneurysm (21% vs 9%, p<0.05). On the other hand, patients with unruptured MCAAs were 6 times more likely than patients with ruptured MCAAs to have a pear-shaped aneurysm (36.3% vs 5.2%, p<0.001). Round-shaped aneurysms were more frequent overall, but they were not significantly more prone to rupture. Conclusion: Although this was a small group of patients, we conclude that transverse elliptic and inverted-pear-shaped aneurysms were more associated with rupture than round/ pear-shaped aneurysms.