Proximal intracranial internal carotid artery branches: prevalence and importance for balloon occlusion test

OBJECT: The aim of this study was to determine the prevalence of angiographically identifiable skull base arterial branches that potentially serve as collateral conduits during a balloon occlusion test (BOT) of the internal carotid artery (ICA). The authors posited that neurological deficits in patients who had previously tolerated the occlusion test may be attributable to an unrecognized collateral support through these channels (operant during proximal ICA BOT) when permanent ICA occlusion was performed more distally. METHODS: In 481 cases (962 ICAs), cerebral angiograms obtained during routine Wada testing were retrospectively reviewed. Two hundred sixty-one patients had at least one angiographically identifiable ICA branch; 109 patients had two or more branches. A meningohypophyseal branch of the cavernous ICA was identified on the right side in 108 patients and on the left in 122. A vidian artery originated from the petrous portion of the ICA on the right side in 58 patients and on the left in 85. The inferolateral trunk revealed itself as a branch of the cavernous ICA on the right side in 17 patients and on the left in 33. A caroticotympanic artery arose from a left cavernous ICA. A persistent trigeminal artery was situated on the right side in two patients and on the left in three. More than half of the patients had angiographically identifiable and perhaps hemodynamically significant skull base branches of the ICA, and approximately one quarter had more than one identifiable branch. CONCLUSIONS: The authors recommend that patients be screened during angiography studies performed prior to BOT in branches of the proximal intracranial ICA and that the site of BOT be moved distally if such branches are identified.