Types of the cerebral arterial circle (circle of Willis) in a Sri Lankan Population

<p>Abstract</p> <p>Background</p> <p>The variations of the circle of Willis (CW) are clinically important as patients with effective collateral circulations have a lower risk of transient ischemic attack and stroke than those with ineffective collaterals. The aim of the present cadaveric study was to investigate the anatomical variations of the CW and to compare the frequency of prevalence of the different variations with previous autopsy studies as variations in the anatomy of the CW as a whole have not been studied in the Indian subcontinent.</p> <p>Methods</p> <p>The external diameter of all the arteries forming the CW in 225 normal Sri Lankan adult cadaver brains was measured using a calibrated grid to determine the prevalence in the variation in CW. Chisquared tests and a correspondence analysis were performed to compare the relative frequencies of prevalence of anatomical variations in the CW across 6 studies of diverse ethnic populations.</p> <p>Results</p> <p>We report 15 types of variations of CW out of 22 types previously described and one additional type: hypoplastic precommunicating part of the anterior cerebral arteries (A1) and contralateral posterior communicating arteries (PcoA) 5(2%). Statistically significant differences (p < 0.0001) were found between most of the studies except for the Moroccan study. An especially notable difference was observed in the following 4 configurations: 1) hypoplastic precommunicating part of the posterior cerebral arteries (P1), and contralateral A1, 2) hypoplastic PcoA and contralateral P1, 3) hypoplastic PcoA, anterior communicating artery (AcoA) and contralateral P1, 4) bilateral hypoplastic P1s and AcoA in a Caucasian dominant study by Fisher versus the rest of the studies.</p> <p>Conclusion</p> <p>The present study reveals that there are significant variations in the CW among intra and inter ethnic groups (Caucasian, African and Asian: Iran and Sri Lanka dominant populations), and warrants further studies keeping the methods of measurements, data assessment, and the definitions of hypoplasia the same.</p

Standardized ultrasound evaluation of carotid stenosis for clinical trials: University of Washington Ultrasound Reading Center

<p>Abstract</p> <p>Introduction</p> <p>Serial monitoring of patients participating in clinical trials of carotid artery therapy requires noninvasive precision methods that are inexpensive, safe and widely available. Noninvasive ultrasonic duplex Doppler velocimetry provides a precision method that can be used for recruitment qualification, pre-treatment classification and post treatment surveillance for remodeling and restenosis. The University of Washington Ultrasound Reading Center (UWURC) provides a uniform examination protocol and interpretation of duplex Doppler velocity measurements.</p> <p>Methods</p> <p>Doppler waveforms from 6 locations along the common carotid and internal carotid artery path to the brain plus the external carotid and vertebral arteries on each side using a Doppler examination angle of 60 degrees are evaluated. The UWURC verifies all measurements against the images and waveforms for the database, which includes pre-procedure, post-procedure and annual follow-up examinations. Doppler angle alignment errors greater than 3 degrees and Doppler velocity measurement errors greater than 0.05 m/s are corrected.</p> <p>Results</p> <p>Angle adjusted Doppler velocity measurements produce higher values when higher Doppler examination angles are used. The definition of peak systolic velocity varies between examiners when spectral broadening due to turbulence is present. Examples of measurements are shown.</p> <p>Discussion</p> <p>Although ultrasonic duplex Doppler methods are widely used in carotid artery diagnosis, there is disagreement about how the examinations should be performed and how the results should be validated. In clinical trails, a centralized reading center can unify the methods. Because the goals of research examinations are different from those of clinical examinations, screening and diagnostic clinical examinations may require fewer velocity measurements.</p

Current trends in cannulation and neuroprotection during surgery of the aortic arch in Europe†‡

OBJECTIVES To conduct a survey across European cardiac centres to evaluate the methods used for cerebral protection during aortic surgery involving the aortic arch. METHODS All European centres were contacted and surgeons were requested to fill out a short, comprehensive questionnaire on an internet-based platform. One-third of more than 400 contacted centres completed the survey correctly. RESULTS The most preferred site for arterial cannulation is the subclavian-axillary, both in acute and chronic presentation. The femoral artery is still frequently used in the acute condition, while the ascending aorta is a frequent second choice in the case of chronic presentation. Bilateral antegrade brain perfusion is chosen by the majority of centres (2/3 of cases), while retrograde perfusion or circulatory arrest is very seldom used and almost exclusively in acute clinical presentation. The same pumping system of the cardio pulmonary bypass is most of the time used for selective cerebral perfusion, and the perfusate temperature is usually maintained between 22 and 26°C. One-third of the centres use lower temperatures. Perfusate flow and pressure are fairly consistent among centres in the range of 10-15 ml/kg and 60 mmHg, respectively. In 60% of cases, barbiturates are added for cerebral protection, while visceral perfusion still receives little attention. Regarding cerebral monitoring, there is a general tendency to use near-infrared spectroscopy associated with bilateral radial pressure measurement. CONCLUSIONS These data represent a snapshot of the strategies used for cerebral protection during major aortic surgery in current practice, and may serve as a reference for standardization and refinement of different approache

CT angiographic study of the role of both willis circle and vertebral arteries during selective cerebral perfusion - a study in 105 patients

Unilateral selective cerebral perfusion (SCP) is a method for cerebral protection in aortic arch surgery. However, variations of the circle of Willis (CoW) could vitiate its protective effect. The aim of our present work was to prospectively analyze variations of CoW and vertebral arteries using CT angiography. From January, 2008 to July, 2008, a total of 105 consecutive patients underwent CT-angiography of the CoW in the Division of Radiology, St. Ekaterina University Hospital of Sofia. There were at least six CoW configurations that could lead to significant hypo perfusion during unilateral SCP: i) type IA - hypoplasia or absence of left posterior communicating artery (PComA) (in 41.9% of the patients); ii) type IB - hypoplasia or absence of anterior communicating artery (AComA) (in 1.9%); iii) type IIA - hypoplasia or absence of both left PComA and AComA (in 6.67%); iv) type IIB - hypoplasia or absence of left P1 or right vertebral artery (VA) (in 6.67%); v) type III - hypoplasia or absence of right A1 (in 8.57%), and vi) type IV - hypoplasia or absence of both right A1 and right VA or both right A1 and left PComA (in 0.95%). All these types were present in a 66.67% of all the examined patients. Our present study showed that CoW variations are presented in significant number of patients. These results support the need of extensive preoperative examination and meticulous intraoperative monitoring of cerebral perfusion during unilateral SCP.Scripta Scientifica Medica 2012; 44(2): 73-77

Anatomical variations of the circle of Willis and their prevalence, with a focus on the posterior communicating artery: A literature review and meta-analysis

The circle of Willis is an anastomotic network of arteries surrounding the base of the brain, providing collateral circulation to prevent ischemia. It has, however, long been established that it exhibits considerable anatomical variation when compared to Thomas Willis' originally described circle. This study aimed primarily to determine an accurate prevalence of the variation of the circle of Willis in the general population and the prevalence of common posterior communicating artery variations. Additional aims were to explain why such a wide range of reported variations exist, and whether different types of studies report significantly different prevalence of variation. A comprehensive literature search identified 764 papers. A three-phase screening process was undertaken, involving a critical analysis of papers, and a total of 33 papers were selected for analysis and literature review. A descriptive statistics test with bootstrap was performed to estimate the average prevalence of variations. The estimated prevalence of general variation, unilateral, and bilateral posterior communicating artery hypoplasia or aplasia was 68.22 ± 14.32%, 19.45 ± 8.63%, and 22.83 ± 14.58%, respectively. Over half of the population exhibit a circle of Willis with some form of variation. To provide a more accurate estimation for the prevalence of variations, a universal classification system needs to be established, collating all the work from high-quality studies, to provide a comprehensive database of the circle's variations. Knowing the prevalence of variations and how they can impact neurosurgical approaches or patterns of ischemic pathology can be crucial in providing effective patient care