Evaluating brain tolerability to carotid artery occlusion.

An objective and practicable method to evaluate the brain tolerance to unilateral carotid artery occlusion was attempted. Ten consecutive cases were studied. Endovascular trial balloon occlusion of the unilateral carotid artery in conjunction with single-photon emission computed tomography (SPECT) as well as digital subtraction angiography (DSA) and clinical neurological evaluation was routinely performed for those patients who might undergo permanent occlusion of the internal (ICA) and/or common carotid artery (CCA). The result of SPECT was analyzed semi-quantitatively and compared with the baseline data as well as the data from contralateral side. The relative symmetry index (rS) of side-to-side radioactivity counts relevant to the baseline was calculated. One subject failed the balloon occlusion test (BOT), even though an angiographically adequate collateral circulation was observed. The rS of the patient was 74.5%. The remaining patients passed the 45-min BOT without any neurological deficiency induced. Their value of rS was 97.8% +/- 4.4%. Based the BOT results, the left ICA, CCA and external carotid artery were excised in one patient, CCA-ICA reconstructions after carotid occlusions were performed in three. The carotid arteries were saved in five. For one patient, the ICA was occluded spontaneously during the BOT. There were no neurological impairments developed after the surgery. With this BOT technique, clinically silent areas of decreased perfusion might be detected. We suggest it be a routine preparatory to carotid manipulations.