How often does an incomplete circle of Willis predispose to cerebral ischemia during closure of carotid artery? Postmortem and clinical imaging studies

A new classification system for the anatomical variations of the human circle of Willis: A systematic review

The circle of Willis (CoW) is an anastomotic arterial network located on the base of the brain. Studies have shown that it demonstrates considerable anatomical variation in humans. This systematic review aimed to identify and catalogue the described anatomical variations of the CoW in humans to create a new, comprehensive variation classification system. An electronic literature search of five databases identified 5899 studies. A two‐phase screening process was performed, and studies underwent quality assessment. A total of 42 studies were included in the review. Data were extracted and circles were reconstructed digitally using graphics software. The classification system contains 82 CoW variations in five continuous groups. Group one contains 24 circles with one or more hypoplastic segments only. Group two contains 11 circles with one or more absent segments only. Group three contains 6 circles with hypoplastic and absent segments only. Group four contains 26 circles with one or more accessory segments. Group five contains 15 circles with other types of anatomical variation. Within each group, circles were subcategorised according to the number or type of segments affected. An original coding system was created to simplify the description of anatomical variations of the CoW. The new classification system provides a comprehensive ontology of the described anatomical variations of the CoW in humans. When used with the coding system, it allows the description and categorisation of recorded and unrecorded variants identified in past and future studies. It is applicable to current clinical practice and the anatomical community, including human anatomy education and research.

The effect of anterior communicating artery flow on neurovascular injury and neurobehavioral outcomes in mice with recurrent stroke

BACKGROUND

Previous studies have estimated that the risk of recurrent stroke was nearly 20% shortly after a transient ischemic attack (TIA) or minor stroke. A missing or hypoplastic (<0.5 mm) anterior communicating artery can have deleterious effects on the brain. Our study aimed to investigate the effect of anterior communicating artery flow on neurovascular injury and neurobehavioral outcomes in mice with recurrent stroke and to identify its underlying mechanisms.

METHODS

A recurrent stroke model was established by an initial cortical infarction followed by a corticostriatal infarction 3 days later. The vascular structure was visualized using synchrotron radiation angiography & magnetic resonance angiography in vivo and transparent endovascular perfusion imaging in vitro. Microvessel perfusion was assessed via fluorescein isothiocyanate perfusion. The infarct volume was measured by magnetic resonance imaging.

RESULTS

The finding that anterior communicating artery flow facilitates pial artery patency in the ipsilateral hemisphere in mice with recurrent stroke suggests that compensatory collateral patency contributes to increased regional cerebral blood flow, enhanced microcirculatory perfusion, improved neurological function and reduced infarct volume.

CONCLUSIONS

The results of this study demonstrate that anterior communicating artery flow alleviates recurrent stroke-induced neurovascular injury and improves neurobehavioral outcomes by promoting the establishment of collateral circulation.

Patient Positioning in Shoulder Arthroscopy: Which is Best?

When performing diagnostic and surgical arthroscopic procedures on the shoulder, the importance of patient positioning cannot be understated. The optimum patient positioning for shoulder arthroscopy should enhance intraoperative joint visualization and surgical accessibility while minimizing potential perioperative risk to the patient. Most shoulder arthroscopy procedures can be reliably performed with the patient either in the lateral decubitus (LD) or beach chair (BC) position. Although patient positioning for shoulder arthroscopy has been subject of controversy, there is no conclusive evidence to suggest superiority of one position versus another. Each position offers advantages and disadvantages and surgeon's experience and training are pivotal on selecting one position versus another. Regardless of the position, a proper positioning of the patient should provide adequate access to the joint while minimizing complications. The purpose of this review is to summarize setup and technical aspects, the advantages and disadvantages, and the possible complications of the LD and BC positions in shoulder arthroscopy.

Routine Shunting During Carotid Endarterectomy in Patients With Acute Watershed Stroke

Aim:

To evaluate the protective role of routine shunting in patients with acute watershed stroke (WS) undergoing carotid endarterectomy (CEA).

Methods:

A total of 138 patients with symptomatic carotid stenosis (SCS) who underwent CEA after acute ischemic stroke from March 2008 to March 2015 were included in this study. Transient ischemic attacks were excluded. These patients were divided into 2 groups according to the topographic pattern of the stroke on magnetic resonance imaging: group 1, territorial strokes (TS) caused by emboli of carotid origin, and group 2, WS caused by a hemodynamic mechanism related to an SCS. Primary end points were 30-day mortality and postoperative neurological morbidity. The insertion of a Pruitt carotid shunt was performed systematically.

Results:

Ninety (65.2%) patients presented a TS of carotid origin and were included in group 1, and 48 (34.8%) of the 138 patients had a WS related to an SCS and were included in group 2. The median time between clinical onset of the cerebral ischemic event and surgery was 9 days (range: 0-89 days). Postoperative mortality was 0%. Seven (5.1%) patients had an aggravation of the neurological status during the postoperative period, of whom 2 presented a complete regression of the symptoms in less than 1 hour (definitive postoperative neurologic morbidity: 3.6%). Postoperative neurologic morbidity rate was significantly higher in the TS group (7 of 90; 7.8%) compared to the WS group (0 of 48; P = .04). No other independent predictive factor of neurologic morbidity after CEA for an SCS was found.

Conclusions:

Our results suggest that routine shunting should be considered in case of acute WS since it may play a protective role. Further studies are eagerly awaited to better define the timing and the best treatment option for both acute WS and TS related to an SCS in order to reduce postoperative neurologic morbidity.

Cerebral watershed infarcts may be induced by hemodynamic changes in blood flow

OBJECTIVES

A watershed infarct is defined as an ischemic lesion at the border zones between territories of two major arteries. The pathogenesis of watershed infarcts, specifically whether they are caused by hemodynamic or embolic mechanisms, has long been debated. In this study, we aimed to examine whether watershed infarcts can be induced by altering the hemodynamic conditions in rats.

MATERIALS AND METHODS

In phase one, to determine the proper clamping duration for a reproducible infarct, 30 rats were equally divided into 5 subgroups and underwent bilateral common carotid artery (CCA) clamping for different durations (0.5, 1.0, 1.5, 2.0, and 3.0 hours). In phase two, to analyze the types of infarcts induced by bilateral CCA clamping, 40 rats were subjected to bilateral CCA clamping for 2 hours. As a control, 8 rats underwent all the operation procedures except bilateral CCA clamping. We performed 7.0T magnetic resonance imaging on the surviving rats on the second day to evaluate the extent of the infarcts. We further identified and examined the infarcts with brain slices stained using 2, 3, 5-triphenyltetrazolium chloride (TTC) on the third day.

RESULTS

After 2 hours of bilateral CCA clamping, cerebral infarction occurred in 42% of surviving rats (13/31). The majority of the ischemic lesions were located in watershed regions of the brain, demonstrated by both MRI and TTC staining.

CONCLUSION

Watershed infarcts were induced through changing hemodynamic conditions by bilateral CCA clamping in rats. This method may lead to the development of a reliable rodent model for watershed infarcts.

Skeleton-based cerebrovascular quantitative analysis

Background

Cerebrovascular disease is the most common cause of death worldwide, with millions of deaths annually. Interest is increasing toward understanding the geometric factors that influence cerebrovascular diseases, such as stroke. Cerebrovascular shape analyses are essential for the diagnosis and pathological identification of these conditions. The current study aimed to provide a stable and consistent methodology for quantitative Circle of Willis (CoW) analysis and to identify geometric changes in this structure.

Method

An entire pipeline was designed with emphasis on automating each step. The stochastic segmentation was improved and volumetric data were obtained. The L1 medial axis method was applied to vessel volumetric data, which yielded a discrete skeleton dataset. A B-spline curve was used to fit the skeleton, and geometric values were proposed for a one-dimensional skeleton and radius. The calculations used to derive these values were illustrated in detail.

Result

In one example(No. 47 in the open dataset) all values for different branches of CoW were calculated. The anterior communicating artery(ACo) was the shortest vessel, with a length of 2.6mm. The range of the curvature of all vessels was (0.3, 0.9) ± (0.1, 1.4). The range of the torsion was (−12.4,0.8) ± (0, 48.7). The mean radius value range was (3.1, 1.5) ± (0.1, 0.7) mm, and the mean angle value range was (2.2, 2.9) ± (0, 0.2) mm. In addition to the torsion variance values in a few vessels, the variance values of all vessel characteristics remained near 1. The distribution of the radii of symmetrical posterior cerebral artery(PCA) and angle values of the symmetrical posterior communicating arteries(PCo) demonstrated a certain correlation between the corresponding values of symmetrical vessels on the CoW.

Conclusion

The data verified the stability of our methodology. Our method was appropriate for the analysis of large medical image datasets derived from the automated pipeline for populations. This method was applicable to other tubular organs, such as the large intestine and bile duct.

Electronic supplementary material

The online version of this article (doi:10.1186/s12880-016-0170-8) contains supplementary material, which is available to authorized users.

A Prospective Nonrandomized Study on Carotid Surgery Performed under General Anesthesia without Intraoperative Cerebral Monitoring

BACKGROUND

The purpose of this study was to assess our experience of carotid surgery habitually performed under general anesthesia without intraoperative intracerebral monitoring, and following a pre-established perioperative protocol, which includes extensive use of an intraoperative shunt (IOS).

METHODS

This study included 311 consecutive carotid operations performed over 32 months. This patient cohort represents 14% of our total experience in carotid surgery (2219 operations, major stroke/mortality rate: 1.4%). The IOS was inserted routinely in the presence of intraoperative blood pressure instability during cross-clamping and when the predictable clamping time might have exceeded 20 minutes. A moderate and stable hypertension was maintained throughout surgery without IOS.

RESULTS

Overall, 120 (38.6%) endarterectomies were performed with primary closure, 73 (23.5%) with eversion technique, 113 (36.3%) with patch angioplasty, and 5 (1.6%) with other techniques. Out of 113 patch angioplasties, 111 (98.2%) were performed with an IOS. This was utilized in only 3 cases of direct carotid reconstructions or other carotid endarterectomy techniques (1.5%). Overall, the IOS placement rate was 36.7%. Postoperatively, 2 major strokes (.64%), 2 minor strokes (.64%), 4 hyperperfusion syndromes (1.3%), and no mortality were recorded. No cases of cross-clamp ischemia/shunt-related perioperative strokes were observed.

CONCLUSIONS

The low perioperative stroke rate reported in this prospective study proves the advantages of wide use of IOS during carotid surgery. This coupled with a large experience in carotid surgery and close monitoring and support of blood pressure, are the major determinants of these results that demonstrate the low risk of shunt-related complications for surgeons who regularly utilize an IOS.

Oxidative Stress and Total Antioxidant Status During Internal Carotid Artery Clamping with or without Shunting: An Experimental Pilot Study

BACKGROUND The exact role of shunting during carotid endarterectomy remains controversial and unclear. The aim of this experimental study was to investigate to what degree carotid clamping may induce changes in the cerebral oxidative status and to focus on the relation of these changes with shunt insertion. MATERIAL AND METHODS Forty New-Zealand rabbits were randomized into 4 groups: group 1 classifying animals with carotid shunt and patent contralateral carotid artery; group 2 shunt and occlusion of the contralateral carotid artery; group 3 no-shunt and patent contralateral carotid artery; and group 4 no-shunt and occlusion of the contralateral carotid artery. Blood samples were collected from the ipsilateral internal jugular vein, immediately after carotid clamping (time 0), and then at 5, 10, 15, 30, and 60 minutes afterwards. Evaluation of oxidative stress was accomplished by measuring the lag-time, representing the initial phase of oxidation, rate of accumulation (RA), showing concentration of free oxygen radical and total antioxidant status (TAS) representing antioxidant composition of serum. RESULTS Lag-time was significantly different in time points 0, 30 and 60 minutes within each different group. TAS was significantly different in time points 0, 15 and 60 min and RA in time points 0, 5, 10 and 60 min within each different group. 60 minutes after carotid clamping, the rate of accumulation as well as lag-time and TAS were increased in all groups, independently of using or not shunting or the presence of contralateral occlusion. After comparing groups 1, 2 and 3 regarding lag-time, TAS and RA, we did not find statistical difference among the groups at any time point. On the contrary, groups 1, 2 and 3 did show significantly different values comparing to group 4 after 60 min of occlusion. CONCLUSIONS Our experimental work based on cerebral metabolism found a significantly higher oxidative stress in models with contralateral carotid occlusion. The use of shunt in all other models did not have any influence on oxidative response. Future human studies should focus on the relation of oxidative status and shunt insertion to determine the benefit of selective or routine shunting during CEA.

A Functional Perspective on the Embryology and Anatomy of the Cerebral Blood Supply

The anatomy of the arterial system supplying blood to the brain can influence the development of arterial disease such as aneurysms, dolichoectasia and atherosclerosis. As the arteries supplying blood to the brain develop during embryogenesis, variation in their anatomy may occur and this variation may influence the development of arterial disease. Angiogenesis, which occurs mainly by sprouting of parent arteries, is the first stage at which variations can occur. At day 24 of embryological life, the internal carotid artery is the first artery to form and it provides all the blood required by the primitive brain. As the occipital region, brain stem and cerebellum enlarge; the internal carotid supply becomes insufficient, triggering the development of the posterior circulation. At this stage, the posterior circulation consists of a primitive mesh of arterial networks that originate from projection of penetrators from the distal carotid artery and more proximally from carotid-vertebrobasilar anastomoses. These anastomoses regress when the basilar artery and the vertebral arteries become independent from the internal carotid artery, but their persistence is not uncommon in adults (e.g., persistent trigeminal artery). Other common remnants of embryological development include fenestration or duplication (most commonly of the basilar artery), hypoplasia (typically of the posterior communicating artery) or agenesis (typically of the anterior communicating artery). Learning more about the hemodynamic consequence that these variants may have on the brain territories they supply may help understand better the underlying physiopathology of cerebral arterial remodeling and stroke in patients with these variants.

Central versus peripheral arterial cannulation and neurological outcomes after thoracic aortic surgery: meta-analysis and meta-regression of 4459 patients

BACKGROUND

Thoracic aortic surgeries remain with high mortality rates, often associated with postoperative neurological complications. The choice of the right cannulation site is extremely important for suitable blood supply and maintenance of vital functions, especially of the central nervous system.

OBJECTIVES

To compare the influence of central versus peripheral arterial cannulation on neurological outcomes in patients undergoing thoracic aortic surgery through systematic review and meta-analysis.

METHODS

MEDLINE, EMBASE, CENTRAL/CCTR, SciELO, LILACS and reference lists of relevant articles were searched for clinical studies that reported in-hospital neurological outcomes after central or peripheral arterial cannulation during thoracic aortic surgery procedures until December 2013. The principal summary measures were Odds Ratio (OR) for central compared to peripheral arterial cannulation with 95% confidence interval (CI) and p-values considered statistically significant when <0.05. The ORs were combined across studies, using the DerSimonian-Laird random effects model and fixed effects model using the Mantel-Haenszel model--both models were weighted. The meta-analysis was completed using the software Comprehensive Meta-Analysis version 2 (Biostat Inc., Englewood, NJ).

RESULTS

Six studies were identified and included a total of 4459 patients (1180 for central and 3279 for peripheral cannulation). There was no significant difference between the central and peripheral groups regarding neurological outcomes. The meta-regression evidenced no relationship between neurological outcomes and the variables age, sex, previous coronary event, previous neurological event, urgency surgery, cardiopulmonary bypass time, activated clotting time and esophageal temperature with p > 0,05.

CONCLUSION

When it comes to neurological outcomes in patients undergoing thoracic aortic surgery, there was no evidence that argues in favor of any choice of arterial cannulation site, which makes us reject any superiority of one approach over the other in this regard.

Internal carotid artery dissection after anterior cervical disc replacement: first case report and literature review of vascular complications of the approach

We report the case of a 41-year-old woman who underwent cervical total disc replacement at C4C5 and C5C6 levels and fusion at C6C7 level through an anterior right-side approach. After anesthesia recovery, the patient presented left hemiparesia and facial palsy due to large right hemispheric stroke. Diffusion-weighted magnetic resonance imaging was performed as soon as the patient developed neurologic symptoms of stroke and revealed a right internal carotid artery dissection. Digital substraction angiography, endovascular stenting, angioplasty and thrombectomy were performed. Six months after treatment, clinical examination showed mild left-arm spasticity. To the best of our knowledge, only two cases of internal carotid artery stroke without dissection or thrombosis are reported. In conclusion, although vascular complications are rare after anterior cervical spine procedure, internal carotid artery dissection can occur. Suspected risk factors are prolonged retraction of the carotid artery and neck extension.

Management of carotid disease in patients undergoing coronary artery bypass surgery: is it time to change our approach?

PURPOSE OF REVIEW

The management of concurrent severe carotid and coronary disease is a subject of ongoing debate in the absence of randomized clinical trials. Amidst the growing controversy, the clinician has to carefully tailor the best strategy for a given patient based on neurologic and cardiac symptoms. This review aims to compile current evidence in this area to help plan strategies for the optimal management of coexisting severe carotid and coronary disease.

RECENT FINDINGS

Carotid revascularization with carotid endarterectomy (CEA) or stenting (CAS) is frequently performed in conjunction with coronary artery bypass surgery (CABG) in the United States for asymptomatic carotid disease. The risk of perioperative stroke with unilateral asymptomatic 70-99% carotid stenosis is likely small based on several observational data. Moreover, the risk associated with both staged and combined CEA-CABG procedures in the asymptomatic population may outweigh any benefit. Carotid artery stenting is an alternative option in patients with severe coronary disease who are considered 'high risk' for CEA. Neurologically symptomatic patients require carotid revascularization prior to or in conjunction with CABG surgery. Ultimately, the choice of carotid revascularization or conservative management will depend on clinical characteristics, anatomy, and local expertise.

SUMMARY

Severe carotid disease in the CABG population is often unilateral and asymptomatic. Based on the available data, conservative carotid therapy in the low-risk asymptomatic individuals is likely the best treatment option. Carotid revascularization may be justified in symptomatic or high-risk patients such as those with contralateral carotid occlusion or bilateral severe stenosis.