Retrograde cerebral embolism.

Cerebral embolism may complicate lesions of the subclavian arteries or aortic isthmus distal to the origins of the vertebral or carotid arteries. This may be due to retrograde propagation of occlusive thrombus. In other cases the vessels are patent but there are periods of reverse blood flow, creating a potential for reflux of embolic material to the ostia of the neck vessels.