Assessment of risk of carotid occlusion with balloon Matas testing and dynamic computed tomography.

Temporary occlusion of the internal carotid artery with a balloon catheter (balloon Matas test) and simultaneous dynamic computerized tomography scanning (DCT) were performed to determine the tolerance of permanent carotid occlusion in eight cerebral aneurysm and two carotid-cavernous fistula (CCF) cases, in whom internal carotid occlusion might be necessary during operation or as a choice of treatment. All patients were evaluated by mean transit time (MTT), especially % transit time (MTT of the occluded side x 100/MTT of the control side). In six patients, % transit time (%TT) was less than 155 and no neurological signs appeared after permanent internal carotid occlusion. Neurological deficit appeared when mean arterial blood pressure was 80, and disappeared when mean arterial blood pressure was 100 during the balloon Matas test in a case whose %TT was 200. Neurological deficit appeared several seconds after the balloon Matas test in a case whose %TT was 250. The critical %TT value to cause symptomatic ischaemia was 200 from our results. Therefore, it is necessary to undertake treatment such as bypass surgery for the patients whose %TT is near 200, even if the balloon Matas test was negative.