[Critical stenosis of the internal carotid artery--which parameters determine prognosis?].

Neurologic symptoms in the region of an internal carotid artery stenosis are due to emboli or the reduction of perfusion pressure. Measurements of cerebral blood flow correlate with perfusion pressure but not with the degree of the stenosis. By transcranial ultrasound sonography the reactivity of the cerebral vascular system can be measured. Thus subgroups of patients may be found who may or may not benefit from the operation. By analysis of color coded duplex sonography, ulcerated stenoses can be detected with high accuracy.