[Pterional approach to the basilar artery aneurysm--with special reference to the accessibility via optic-carotid...

There have been known two routes in pterional approach to the distal basilar artery aneurysms: one is via the space between the optic nerve and internal carotid artery (optic-carotid triangle: OCT) and the other is lateral to the ICA (retrocarotid approach: RCA). Although the approach via OCT has several advantages of its own, it had been considered to be used in very limited cases. Since we successfully clipped the aneurysms via OCT in 4 cases out of 12 (33%), neuroradiological findings observed in these 4 cases are analyzed and reported. Measurements were made in the following items on the carotid angiogram of the cases operated via OCT (OCT group) and RCA (RCA group): the distance of ICA bifurcation from midline (D), height of ICA bifurcation from the base line between anterior and posterior clinoid processes (H). Although these two values seemed higher in OCT group than those in RCA group, no significant difference was found. The product of D and H (D X H) was observed to be significantly higher in OCT group than in RCA group. The value of D X H is considered one of the indicators of the size of OCT and is proved to be useful to judge whether approach via OCT is applicable or not. Values of D X H obtained from cases with aneurysm increase with age. Regression line calculated between age and D X H value suggests that more than half of the patients over 45 years of age should have space in OCT wide enough to apply clips to the aneurysms.(ABSTRACT TRUNCATED AT 250 WORDS)