Vertebrobasilar transient ischemic attacks in internal carotid artery occlusion or tight stenosis.

We studied 12 patients with internal carotid artery (ICA) occlusion or tight stenosis but without vertebrobasilar and subclavian atherosclerosis who suffered vertebrobasilar insufficiency (VBI). The patients with ICA occlusion were compared with a sex- and age-matched control group that had ICA occlusion but no VBI. Visible infarct on computed tomographic scan, greater size of visible infarct, weak collateral circulation, and bilateral atherosclerosis of the ICA significantly correlated with the occurrence of VBI. No significant difference was demonstrated for emboligenic lesions, but posterior to anterior flow through the posterior communicating arteries was demonstrated only in the patients with VBI. These facts suggested hemodynamic disturbances with "steal VBI." In ICA tight stenosis, VBI symptoms disappeared after endarterectomy but persisted in patients with more than 50% stenosis; this was also suggestive of hemodynamic VBI. Vertebrobasilar insufficiency had a prognostic significance, being associated with an increased occurrence of delayed stroke.