Assessment of the posterior communicating artery by transcranial color-coded duplex sonography

The aim of this study was to investigate flow velocity and flow direction in the posterior communicating artery (PcomA) by means of transcranial color-coded duplex sonography (TCCD) and to compare the results with angiographic findings.

Thirty patients with unilateral occlusion of the internal carotid artery (ICA) due to atherosclerosis (n=15) or balloon occlusion (n=15) and 50 normal subjects were included. The circle of Willis was insonated through the temporal bone window. In 24 patients with unilateral ICA occlusion, angiograms were available and were compared with the results of TCCD.

The PcomA could be detected unilaterally in 70% of normal subjects and bilaterally in 30%. A retrograde flow direction in the PcomA from the posterior cerebral artery to the ICA was found in 75% of the normal control subjects. The mean peak flow velocity in normal PcomAs was 36 +/- 15 cm/s (+/- SD). No significant differences in flow velocity were found between unilaterally and bilaterally detectable PcomAs or between retrograde and orthograde PcomAs. In patients with unilateral ICA occlusion we observed ipsilaterally a retrograde flow direction, with an elevation of flow velocity (64 +/- 10 cm(s) compared with the contralateral side (27 +/- 14 cm/s; P<.001).

TCCD appears to be a valuable method to determine flow velocity and flow direction not only in the large intracranial vessels but also in the smaller communicating arteries. In the future this method could be useful for the planning of ICA balloon occlusions and in deciding whether to perform extracranial/intracranial bypass surgery. It could furthermore show intracranial collaterals in patients with cerebrovascular disease and help to estimate the risk of watershed infarctions in patients with asymptomatic high-grade ICA stenosis and in patients undergoing carotid endarterectomy.