Delayed TIAs distal to bilateral occlusion of carotid arteries -- evidence for embolic and hemodynamic mechanisms.

We studied 4 patients with bilateral carotid artery occlusion who suffered delayed TIAs in one of the occluded internal carotid or common carotid areas. Hemodynamic mechanisms were prominent in two patients, in head turning and orthostatic hypotension. In the other two cases, embolic phenomena through the homolateral external carotid collateral pathways were probable, because this artery (or the common carotid artery) showed atheromatous stenosis and major collateral supply to the brain and retina. Different mechanisms may be responsible for further ischemia after bilateral occlusion of carotid arteries.