Intravenous digital subtraction angiography: an index of collateral cerebral blood flow in internal carotid artery occlusion.

The objective of this investigation was to correlate Xenon-133 inhalation rCBF measurements with the pattern of cortical arterial filling on intravenous DSA in 18 patients with unilateral internal carotid artery occlusion. Of 9 patients showing symmetrical filling of hemispheric cortical arteries, none showed an inter-hemispheric difference in rCBF ( delta Fg) greater than 10ml/100gm/min. Of 9 patients showing delayed cortical opacification ipsilateral to the internal artery occlusion, 3 showed a delta Fg greater than 10ml/100gm/min, 3 showed a delta Fg in the 7-10ml/100gm/min range, and 3 had a delta Fg less than 7ml/100gm/min. All patients with asymmetric abnormalities in the rCBF profile had the delayed pattern of cortical filling on DSA. The presence of symmetrical hemispheric opacification of cortical arteries on DSA indicates adequate interhemispheric redistribution of rCBF and patent inter-hemispheric collateral channels, but not necessarily normal cerebral blood flow. The presence of delayed cortical arterial opacification on the side of internal carotid artery occlusion does not necessarily imply significant inter-hemispheric rCBF differences, nor does it rule out a normal rCBF. The presence of bilateral reduction of rCBF and symmetrical cortical artery filling on DSA may represent an "interhemispheric steal".