Haemodynamic evaluation of the cerebral circulation by periorbital Doppler examination and cerebral blood flow (CBF) measurement in carotid artery disease

To assess the haemodynamic significance of an internal carotid artery (ICA) stenosis, angiography or direct ultrasound examination should be supplemented by indirect physiologic testing of the collateral circulation. Among the tests proposed, we used the periorbital flow direction, assessed by Doppler technique, and cerebral blood flow reactivity to vasodilation, by i.v. xenon-133 technique, in 35 patients before carotid endarterectomy. The results were related to the actual perfusion pressures, measured during surgery in the distal ICA. All 15 patients with normal orthograde periorbital flow had normal cerebral blood flow (CBF) vasoreactivity and no, or only minor, reduction in ICA perfusion pressure. Of the 20 patients with inverted flow, 12 had normal and 8 had abnormal CBF reactivity. These 8 patients proved to have significantly lower cerebral perfusion pressures, as compared with the remaining 12 patients with inverted periorbital flow (p less than 0.001), who in turn had lower perfusion pressures than the 15 patients with orthograde flow (p less than 0.005). Based on these results, we suggest periorbital Doppler examination as a haemodynamic adjunct to direct ICA visualization. A normal orthograde flow will most certainly rule out any severe pressure reduction. By measuring CBF at rest and following vasodilation in cases with inverted flow, most patients with severe reduction in cerebral perfusion pressure may be identified.