Magnetic Resonance Angiography-based Prediction of the Results of Balloon Test Occlusion

Precautious balloon test occlusion (BTO) is sometimes performed in cases of high-risk intraoperative internal carotid artery injury. We investigated whether magnetic resonance angiography (MRA) findings could predict BTO results to thus avoid the use of precautious BTO. This retrospective study, included 96 patients who underwent BTO, eight of whom underwent bilateral BTO. The relationship between the BTO results for 104 internal carotid arteries and the MRA findings obtained in 96 patients were retrospectively evaluated. On MRA, anterior cerebral artery (A1)–anterior communicating artery–A1 was defined as anterior collateral circulation (ACC), and posterior cerebral artery–posterior communicating artery was defined as posterior collateral circulation (PCC). BTO was tolerated in all 27 sides with thick ACC regardless of PCC thickness. In 31 of 44 cases with a thin ACC, the tested sides were BTO-tolerant (70.5%). Of these 44 tested sides, all five with a thick PCC were BTO-tolerant, but eight with a thin PCC and 31 with an invisible PCC showed results other than tolerance. Among cases with an invisible ACC, 10 of 33 tested sides were BTO-tolerant (30.3%). Among these 33 tested sides, outcomes other than tolerance were observed regardless of PCC thickness. Thick, thin, and invisible ACCs were assigned 3, 1, and 0 points, respectively; and thick, thin, and invisible PCCs were assigned 2, 1, and 0 points, respectively. A sum of 3 points in the ACC and PCC indicated that all sides were BTO-tolerant. In conclusion, a thick ACC or a thin ACC with a thick PCC indicates BTO-tolerance. The BTO prediction score is useful for predicting results of BTO.