Angiography Analysis of Variations of the Posterior Segment of the Circle of Willis

Abstract

Cerebral-vascular diseases present one of the leading problems of the modern mankind. They are followed by the risk of high mortality rate, and as such cause high level of disability with people who survive cerebral-vascular incident (stroke, apoplexy). Researches done so far proved that beginning, course and result of the cerebral-vascular diseases depend immensely of the possibility to establish collateral blood circulation and first of all on so called tertian level that is actually the circle of Willis. The circle of Willis, thanks to communicating segments, provide detour way to procure parts of the brain which, due to insufficiency, do not get enough quantity of blood. In this particular study by the analysis of 150 MRI patient's angiographies of the circle of Willis that had been processed at the Radiology Institute of the Clinic Center of University in Sarajevo, we tried to present the most common variations of the posterior segment of the circle of Willis with patients who did not have signs of the cerebral-vascular diseases. The analysis included two target groups (above 60 years old and younger than 34 years old) and both genders. By the analysis of the angiographies of the circle of Willis we reached following results: complete posterior configuration of the circle of Willis has been found with all patients in 54% of cases, but in some slightly higher percentage complete posterior configuration is noted with younger category of patients compared to elderly patients, and in some higher percentage with female compared to male patients. Out of variations that damage the posterior segment of the circle of Willis the first one, according to the frequency of occurring, is the variation of the type of unilateral fetal sort of posterior cerebral artery, and then the variation marked as unilateral aplasia or hypoplasia of the posterior communicating artery.

Plasticity of Circle of Willis: A Longitudinal Observation of Flow Patterns in the Circle of Willis One Week after Stenting for Severe Internal Carotid Artery Stenosis

“…The P1 segment of the PCA was the precommunicating segment of the PCA. The incidence of P1 hypoplasia measured 3% in an autopsy study of Voljevica et al [7]. To the best of our knowledge, no reports have mentioned the probability of dynamic transformation in a P1 segment.…”

“…We emphasize that despite the critiques of time-of-flight MRA in the literature, the modality is of interest precisely because of these flow effects [7, 8]. …”

Anatomical variations of circle of Willis - a cadaveric study

“…The circle of Willis, through its communicating segments, provides an alternative route for the blood to reach parts of the brain which, due to insufficiency, do not receive enough quantity of blood. 38 However, in cases such as the one reported here, due to the absence of communicating arteries, the alternative routes may not be available.…”

Associations between Circle of Willis Morphology and White Matter Lesion Load in Subjects with Carotid Artery Stenosis

“…1 and 2). The diagnosis of A1, PCoA and P1 segment hypoplasia was based on MRA (if <1 mm in diameter, including segments not visible on MRA) [7]. FLAIR imaging (18,000/119/2,000 [inversion time ms]) was performed with two signals acquired (acquisition time of 4 min 24 s for 15 sections, echo train length of seven, 180–224 × 256 matrix, and a field of view of 150–220 mm).…”

“…Applying the WML load scoring method designed by Fazekas et al [6] and the criteria of CoW anomaly defined by magnetic resonance angiography (MRA) [7], we hypothesized that CoW anomalies may contribute to LA in victims of severe carotid artery stenosis through impaired cerebral autoregulation. …”