Collateral Variations in Circle of Willis in Atherosclerotic Population Assessed by Means of Transcranial Color-Coded Duplex Ultrasonography

Abstract

Background and Purpose-Transcranial color-coded duplex ultrasonography combined with common carotid artery (CCA) compression can be used to assess the collateral function of the circle of Willis. The aim of this study was to assess the unknown fraction of hemodynamic functional anterior and posterior communicating arteries (AcoA and PcoA, respectively) in an atherosclerotic population with no cerebrovascular symptoms. Methods-In 76 patients with a mean age of 61 (35 to 89) years, the blood flow velocity changes in the precommunicating parts (A1 and P1, respectively) of the anterior and posterior cerebral arteries were measured during CCA compression. The AcoA was defined as functional if blood flow was reversed in the ipsilateral A1 and enhanced in the contralateral A1 during CCA compression. The PcoA was defined as functional if the flow velocity in the P1 was enhanced Ͼ20% during ipsilateral CCA compression. Results-It was possible to assess cross flow through the anterior part of the circle of Willis in 95% of the subjects. Failure of this collateral pathway was caused by a hypofunctional AcoA in 4% and a hypofunctional A1 in 1% of the subjects. Anomalies in the posterior part of the circle of Willis hampering collateral flow from the basilar to the internal carotid artery were found in 45% of the hemispheres. Thirty-eight percent of PcoAs were hypofunctional, and 7% of the posterior cerebral arteries had a persistent fetal anatomy. Conclusions-We found that in subjects with no cerebrovascular symptoms, the anterior collateral pathway of the circle of Willis was nearly always functional. In contrast, the posterior collateral pathway was nonfunctional in almost half of the total number of hemispheres. Comparing these basic data with data from patients with cerebral ischemic disease might further help to elucidate the importance of the collateral capacity of the circle of Willis.

Configurations of the circle of Willis: a computed tomography angiography based study on a Polish population

“…Bilateral lack of PComAs was the most frequent posterior variant published in the literature [6,[12][13][14], although its prevalence varied. This variant was reported in about 30.00% of the subjects undergoing CTA examinations, which was twice as often as in the aforementioned MRA and TCCD studies [6,9]. The incidence of FTP has been reported as ranging from 11.20% to 18.00% in different studies [6,14], whereas in the present study it was found to occur in 16.40% of the cases.…”

“…Conclusions based on the comparison of data acquired using different methods seem to be questionable. This is due to the fact that each particular evaluation technique has different characteristics and limitations [5,6,9]. Furthermore, it should be noted that a number of previously published studies were carried out on patients with cerebrovascular disorders [3,6,8,11].…”

“…The prevalence of a closed anterior circle ranged from 74.00% to 83.00% (Table 4) in the studies cited. The posterior component of the circle was incomplete in approximately half of the subjects in two MRA-based studies [6,14] and one TCCD-based [9] study. The present study, as well as the CTA-based research carried out by Li et al [13], showed a noticeably higher occurrence of an open posterior part of the CW (Table 4).…”

“…Cadaveric studies are still widely performed [4,5,11,15] and several imaging methods, including transcranial colour-coded duplex ultrasonography (TCCD) [9], 3-dimensional time-of-flight magnetic resonance angiography (3D-TOF-MRA) [2,3,14], and computed tomography angiography (CTA) [2,7,13,16] have been used to examine the circle. These imaging techniques have allowed for the precise depiction of the clinically relevant collaterals of the circle by assessing the patency of blood vessels that determine the circle's physiological completeness.…”

Transcranial Doppler findings in middle cerebral arterial occlusive disease in relation to degree of stenosis and presence of concomitant stenoses

“…19 TCCD has been reported to be a valuable method to detect stenoses of less than 50% in large intracranial vessels, with a high accuracy, 22 and to assess the collateral function of smaller communicating vessels. 23,24 Furthermore, TCCD enables the sonographer to correct the angle of insonation, which could be larger than expected in elderly patients with tortuous vessels, in patients with intracranial stenosis, and when a mass effect is present. 25 Thus, TCCD may play a role in complicated MCA lesions.…”