Arterial collateral anatomy predicts the risk for intra-operative changes in somatosensory evoked potentials in patients undergoing carotid endarterectomy: a prospective cohort study.

BACKGROUND: During carotid endarterectomy (CEA), significant amplitude decrement of somatosensory evoked potentials (SEPs) is associated with post-operative neurological deficits. OBJECTIVE: To investigate the association between an incomplete circle of Willis and/or contralateral ICA occlusion and subsequent changes in intra-operatively monitored SEPs. METHODS: We performed a retrospective analysis of a single center, prospective cohort of consecutive patients undergoing CEA over a 42-month period after reviewing the collateral arterial anatomy on pre-operative radiological imaging. The primary endpoint was an intra-operative decline in SEPs > 50% compared to the baseline value during arterial cross-clamping. Univariate and multivariate logistic regression analyses were performed to investigate a potential association between contralateral ICA occlusion, incomplete circle of Willis, and subsequent alteration in SEPs. RESULTS: A total of 140 consecutive patients were included, of which 116 patients (82.9%) had symptomatic carotid stenosis of at least 50% according to the classification used in the North American Carotid Surgery Trial (NASCET) (Stroke 22:711-720, 1991). Six patients (4.3%) showed contralateral ICA occlusion, 22 patients (16%) a missing/hypoplastic anterior communicating artery (Acom) or A1 segment, and 79 patients (56%) a missing ipsilateral posterior communicating artery (Pcom) or P1 segment. ICA occlusion and missing segments of the anterior circulation (missing A1 and/or missing Acom) were associated with the primary endpoint (p = 0.003 and p = 0.022, respectively). CONCLUSION: Contralateral ICA occlusion and missing anterior collaterals of the circle of Willis increase the risk of intra-operative SEP changes during CEA. Pre-operative assessment of collateral arterial anatomy might help identifying patients with an increased intra-operative risk.

Repaired coarctation of the aorta, persistent arterial hypertension and the selfish brain.

BACKGROUND: It has been estimated that 20-30% of repaired aortic coarctation (CoA) patients develop hypertension, with significant cardiovascular morbidity and mortality. Vertebral artery hypoplasia (VAH) with an incomplete posterior circle of Willis (ipCoW; VAH + ipCoW) is associated with increased cerebrovascular resistance before the onset of increased sympathetic nerve activity in borderline hypertensive humans, suggesting brainstem hypoperfusion may evoke hypertension to maintain cerebral blood flow: the "selfish brain" hypothesis. We now assess the "selfish brain" in hypertension post-CoA repair. METHODS: Time-of-flight cardiovascular magnetic resonance angiography from 127 repaired CoA patients (34 ± 14 years, 61% male, systolic blood pressure (SBP) 138 ± 19 mmHg, diastolic blood pressure (DBP) 76 ± 11 mmHg) was compared with 33 normotensive controls (42 ± 14 years, 48% male, SBP 124 ± 10 mmHg, DBP 76 ± 8 mmHg). VAH was defined as < 2 mm and ipCoW as hypoplasia of one or both posterior communicating arteries. RESULTS: VAH + ipCoW was more prevalent in repaired CoA than controls (odds ratio: 5.8 [1.6-20.8], p = 0.007), after controlling for age, sex and body mass index (BMI). VAH + ipCoW was an independent predictor of hypertension (odds ratio: 2.5 [1.2-5.2], p = 0.017), after controlling for age, gender and BMI. Repaired CoA subjects with VAH + ipCoW were more likely to have difficult to treat hypertension (odds ratio: 3.3 [1.01-10.7], p = 0.049). Neither age at time of CoA repair nor any specific repair type were significant predictors of VAH + ipCoW in univariate regression analysis. CONCLUSIONS: VAH + ipCoW predicts arterial hypertension and difficult to treat hypertension in repaired CoA. It is unrelated to age at time of repair or repair type. CoA appears to be a marker of wider congenital cerebrovascular problems. Understanding the "selfish brain" in post-CoA repair may help guide management. JOURNAL SUBJECT CODES: High Blood Pressure; Hypertension; Magnetic Resonance Imaging (MRI); Cardiovascular Surgery; Cerebrovascular Malformations.

Efficacy and Safety of Willis Covered Stent for Treatment of Complex Vascular Diseases of the Internal Carotid Artery.

BACKGROUND: Willis covered stents are used in clinical practice for some complex cerebrovascular diseases. However, the performance of the Willis covered stent requires further investigation. In this study, we investigate the safety and efficacy of Willis covered stents for the treatment of complex vascular diseases of the internal carotid artery (ICA). METHODS: Thirteen patients with complex ICA diseases treated with the Willis covered stent system at our institution from October 2016 to January 2018 were analyzed retrospectively. Follow-up observation and digital subtraction angiography (DSA) examination were conducted at about 6-10 months after the treatment. RESULTS: The complex vascular diseases of the ICA were successfully treated in 12 patients. The technical success rate was 92.3%. Pathologically, 13 lesions included blood blister-like aneurysm (n = 7), traumatic pseudoaneurysm (n = 1), traumatic carotid artery rupture (n = 1), and aneurysm with arteriovenous fistula (n = 4). Thirteen patients with complex vascular diseases of the ICA were treated with 15 Willis covered stents. The release sites of Willis covered stents were the C7 (n = 2), C6 (n = 1), C5 and/or C4 (n = 9), and the C2 (n = 3) segment of the ICA. DSA performed immediately after stent deployment revealed that complete occlusion of the lesion was achieved in 11 patients and endoleak was observed in 2 patients. Of the 11 patients, postoperative DSA examination indicated that the lesions were occluded completely. Among 2 patients, who had a second stent implantation at the break of the ICA, the traumatic ICA rupture was essentially completely obstructed in 1 patient. The endoleak remained in 1 patient with carotid cavernous sinus fistula because the placement of the second stent system was difficult with his ICA tortuosity. No recurrence of aneurysms, hemorrhagia, and other lesions was observed, and the patients' parent arteries were patent without stenosis. No procedure-related complications or deaths occurred during follow-up. CONCLUSIONS: For the treatment of complex vascular diseases in the ICA, Willis covered stent implantation is safe and effective. However, longer follow-up, large-sample controlled studies, and multicenter studies are needed for further confirmation.

A functional assessment of the circle of Willis before aortic arch surgery using transcranial Doppler.

BACKGROUND: Antegrade selective cerebral perfusion (ASCP) with systemic moderate hypothermia is routinely used as brain protection during aortic arch surgery. Whether ASCP should be delivered unilaterally (u-ASCP) or bilaterally (bi-ASCP) remains controversial. METHODS: We routinely studied the functional anatomy of the circle of Willis (CoW in all patients scheduled for arch surgery using transcranial color-coded Doppler over a decade. On the basis of these data, we classified observed functional variants as being "safe," "moderately safe," or "unsafe" for u-ASCP. RESULTS: From January 2005 to June 2015, 1119 patients underwent aortic arch surgery in our institution. Of these, 636 patients had elective surgery performed with ASCP. Preoperative full functional assessment of the CoW was possible in 61% of patients. A functionally complete CoW was found in only 27%. Of all variants, 72% were classified as being safe for u-ASCP, whereas 18% were moderately safe for u-ASCP, and 10% unsafe. Unsafe variants for bi-ASCP were observed in 0.5% of patients. CONCLUSIONS: The risk of ischemic brain damage due to malperfusion is estimated to be substantially higher during right u-ASCP than during bi-ASCP. Bi-ASCP is therefore highly preferable over u-ASCP if the function of the CoW is unknown. We propose a tailored approach using this full functional assessment preoperatively by applying u-ASCP via the right subclavian artery when considered safely possible, and bi-ASCP when considered a necessity to prevent cerebral malperfusion, and thus thereby try to reduce the embolic stroke risk of ostial instrumentation in bi-ASCP.

Incomplete circle of Willis is associated with a higher incidence of neurologic events during carotid eversion endarterectomy without shunting.

OBJECTIVE: A complete circle of Willis (CoW) is considered an important collateral network to maintain blood flow during cross-clamping in carotid endarterectomy (CEA). The aim of this study was to evaluate the impact of an incomplete CoW with isolated middle cerebral artery (iMCA) on immediate neurologic events (INEs) after CEA. METHODS: We prospectively collected the clinical data and outcomes of 902 patients who underwent CEA under general anesthesia between 2013 and 2015. All patients had preoperative computed tomography angiography of the extracranial and intracranial cerebral circulation. Indications were asymptomatic (52%) and symptomatic (48%) carotid artery disease. Patients who had CEA with shunt (n = 35) and those with inadequate intracranial imaging to assess CoW were excluded (n = 322) only. Computed tomography angiography images were reviewed retrospectively and independently by two vascular radiologists who were blinded for treatment outcomes. Imaging assessment included the vertebral and carotid circulation and each segment of the CoW, which was classified as normal, hypoplastic (diameter < 0.8 mm) or absent. The ipsilateral MCA was considered isolated if there was an absence of the anterior and posterior communicating branches from the contralateral carotid or posterior circulations. INE was defined as any transient ischemic attack (TIA) and stroke diagnosed immediately after the procedure. RESULTS: Of the 545 included patients (331 males; mean age, 69 ± 8 years), 12 (2.2%) had a stroke in the postoperative period. There were 20 INEs (8 strokes and 12 TIAs). A complete CoW was rare; it was only detected in 19 patients (3.5%) and an iMCA was found in 34 patients (6.3%). When at least one collateral circulation was complete (in 330 patients), we observed only four INEs (1.2%). Of the 34 patients with an iMCA, 8 (24%) had INE (6 TIAs and 2 strokes). Overall, iMCA was an independent predictor of INEs (odds ratio, 11.12; 95% confidence interval, 3.57-35.87; P < .001). With logistic regression, the model included hypertension, smoking, diabetes, hyperlipidemia, carotid clamping time (minutes), contralateral significant internal carotid artery stenosis of greater than 90%, ipsilateral significant internal carotid artery stenosis of greater than 90%, preoperative symptoms in 6 months, and iMCA; above iMCA only symptomatic patients had significant risk (odds ratio, 3.34; 95% confidence interval, 1.19-9.73; P = .02), whereas all other parameters were not significant. CONCLUSIONS: An iMCA carries more than a 10-fold higher the risk of INEs after CEA with cross-clamping without shunt protection. In these patients, routine shunting is recommended to prevent INEs.

Quantitative assessment of changes in hemodynamics of the internal carotid artery after bypass surgery for moyamoya disease.

OBJECTIVE Although intracranial vessel remodeling has been observed in moyamoya disease, concerns remain regarding the effect of bypass surgery on hemodynamic changes within the internal carotid artery (ICA). The authors aimed to quantify the surgical effect of bypass surgery on bilateral ICAs in moyamoya disease and to estimate pressure drop (PD) along the length of the ICA to predict surgical outcomes. METHODS Records of patients who underwent bypass surgery for treatment of moyamoya disease and in whom flow rates were obtained pre- and postsurgery by quantitative MR angiography were retrospectively reviewed. Quantitative MR angiography and computational fluid dynamics were applied to measure morphological and hemodynamic changes during pre- and postbypass procedures. The results for vessel diameter, volumetric flow, PD, and mean wall shear stress along the length of the ICA were analyzed. Subgroup analysis was performed for the circle of Willis (CoW) configurations. RESULTS Twenty-three patients were included. The PD in ICAs on the surgical side (surgical ICAs) decreased by 21.18% (SD ± 30.1%) and increased by 11.75% (SD ± 28.6%) in ICAs on the nonsurgical side (contralateral ICAs) (p = 0.001). When the PD in contralateral ICAs was compared between patients with a complete or incomplete CoW, the authors found that the PDI in the former group decreased by 2.45% and increased by 20.88% in the latter (p = 0.05). Regression tests revealed that a greater postoperative decrease in PD corresponded to shrinking of ICAs (R2 = 0.22, p = 0.02). CONCLUSIONS PD may be used as a reliable biomechanical indicator for the assessment of surgical treatment outcomes. The vessel remodeling characteristics of contralateral ICA were related to CoW configurations.

Endarterectomía carotídea con medición de presión de muñón, manejo hemodinámico y uso selectivo de shunt / Carotid Endarterectomy with routine carotid stump pressure measurement, intraoperative hemodynamic management and selective use of shunt

Resumen Introducción En la endarterectomía carotídea (EC) durante el clampeo, la perfusión cerebral se mantiene por circulación contralateral a través del Polígono de Willis, que se relaciona con la presión de muñón carotídeo (PM). Si ésta es menor a 50 mmHg existe riesgo de Accidente Cerebrovascular (ACV) por hipoperfusión y está indicado uso de shunt para asegurar suficiente circulación cerebral, pero también se puede elevar transitoriamente la presión arterial sistémica haciendo innecesario el uso de shunt. Objetivo Mostrar los resultados de EC con medición de PM para evaluar la perfusión cerebral del hemisferio clampeado con manejo hemodinámico intraoperatorio minimizando el uso de shunt. Material y Métodos Estudio retrospectivo de 73 pacientes sometidos a EC bajo anestesia general con medición de PM, manejo hemodinámico intraoperatorio y uso selectivo de shunt. Se analizaron variables demográficas, clínicas y morbimortalidad perioperatoria. Resultados 73 pacientes, edad promedio 71,1 años, 69,9% sintomáticos. En 54 pacientes la PM fue superior a 50 mmHg y no se usó shunt, en 19 la PM fue menor a 50 mmHg y con manejo hemodinámico intraoperatorio se elevó en 16 que no requirieron shunt. Sólo en 3 casos la PM no alcanzó los 50 mmHg y se usó un shunt de Pruitt-Inahara. Dos pacientes sintomáticos presentaron déficit neurológico central transitorio postoperatorio y 2 pacientes fallecieron por infarto cardíaco. Conclusión La EC con medición de PM y manejo hemodinámico minimizó el uso de shunt transitorio y fue un procedimiento seguro para tratar los pacientes con estenosis carotídea con indicación quirúrgica.

Introduction During carotid endarterectomy (CEA) clamping cerebral perfusion is maintained by contralateral circulation through the Circle of Willis and it is correlated to the stump pressure (SP). If it is below 50 mmHg there is risk of stroke due to hypoperfusion and a shunt must be used, but systemic blood pressure can be temporarily elevated making the use of shunt unnecessary. Aim Results of CEA with SP measurement to evaluate cerebral perfusion in cross-clamped hemisphere and hemodynamic intraoperative management reducing the use of shunt. Material and Methods Retrospective study of CEAs performed in 73 patients under general anaesthesia with SP measurement, hemodynamic management and selective use of shunt. Demographics, clinical and perioperative morbimortality variables were analized. Results 73 patients, average age 71.1 years, 69.9% symptomatic. In 54 patients SP was above 50 mmHg and shunt was not used, in 19 SP was below 50 mmHg, it was elevated through intraoperative hemodynamic management and shunt was not needed. In only 3 cases SP did not reach 50 mmHg and a Pruitt-Inahara shunt was used. Two patients presented postoperative transient central neurological deficit and 2 died due to myocardial infarction. Conclusion CEA with SP measurement and hemodynamic management reduced the use of carotid shunting and it was a safe procedure to treat patients with severe carotid stenosis who need surgical intervention.

Patterns of Acute Ischemic Strokes After Carotid Endarterectomy and Therapeutic Implications.

AIM: Acute ischemic strokes following surgical treatment of carotid stenosis lead to substantial disability and mortality, and vascular mechanisms underlying their development are not fully elucidated. The goal of this study was to analyze the topographic patterns of acute ischemic stroke following carotid endarterectomy (CEA) on diffusion-weighted and perfusion-weighted magnetic resonance imaging (MRI). MATERIAL AND METHODS: Data were retrospectively collected from consecutive patients who underwent CEA and developed postoperative acute ischemic stroke. Based on the MRI data sets, the lesion patterns of acute stoke were characterized. Morphology of the circle of Willis, the 3-D time-of-flight (3D-TOF) of the cerebral arteries, and status of the carotid circulation were also analyzed in order to determine the vascular mechanisms involved in stroke development. RESULTS: Between January 2008 and May 2015, 821 patients were treated surgically for a symptomatic or asymptomatic carotid stenosis at the University Hospital of Nice. Nineteen (2.3%) patients had an acute ischemic stroke after surgery. Among them, 11 (57.9%) patients had a territorial infarction and 8 (42.1%) patients had an internal watershed infarction, cortical watershed infarction, or mixed border zone infarction. According to imaging data sets, embolic mechanism of stroke was reported for 12 (63.2%) patients, hemodynamic mechanism for 2 (10.5%) patients, and mixed mechanism for 5 (26.3%) patients. An asymmetry on 3D-TOF was observed in 60% and 50% of patients with hemodynamic and mixed stroke and in 25% of patients with embolic stroke. The latter 2 patients with embolic stroke underwent successful mechanical thrombectomy using stent-retriever devices. CONCLUSION: In this cohort, embolic mechanism leading to postoperative stroke was more frequently observed than hemodynamic mechanism. Immediate characterization of the cerebral lesion by postoperative brain MRI is of utmost importance because it may rapidly identify patients eligible for treatments such as mechanical thrombectomy.

The circle of Willis predicts the antihypertensive effects of carotid artery stenting.

OBJECTIVE Carotid artery stenting (CAS) has antihypertensive effects, but the durability and degree of this response remain variable. The authors propose that this clinical variability is a function of the presence or absence of a complete circle of Willis (COW). Incomplete COWs perfuse through a higher-resistance pial collateral pathway, and therefore patients may require a higher mean arterial pressure (MAP). Carotid artery revascularization in these patients would reduce the end-organ collateral demand that has been hypothesized to drive the MAP response. METHODS Using a retrospective, nonrandomized within-subject case-control design, the authors compared the postoperative effects of CAS in patients with and without a complete COW by using changes in MAP and antihypertensive medication as end points. They recorded MAP and antihypertensive medications 3 months prior to surgery, preoperatively, immediately postoperatively, and at the 3-month follow-up. RESULTS Data were collected from 64 consecutive patients undergoing CAS. Patients without a complete COW (25%) were more likely to demonstrate a decrease in BP response to stenting (i.e., a drop in MAP of 10 mm Hg and/or a reduction or cessation of BP medications at 3 months postoperatively). Of the patients in the incomplete COW cohort, 75% had this outcome, whereas of those in the complete COW cohort, only 41% had it (p < 0.041). These findings remained statistically significant in a logistic regression analysis for possible confounders (p < 0.024). A receiver operating curve analysis of preoperative data indicated that a MAP > 96.3 mm Hg was 55.5% sensitive and 57.4% specific for predicting a complete COW and that patients with a MAP > 96.3 mm Hg were more likely to demonstrate a good MAP decrease following CAS (p < 0.0092). CONCLUSIONS CAS is associated with a significant decrease in MAP and/or a reduction/cessation in BP medications in patients in whom a complete COW is absent.

Molecular adaptations in vasoactive systems during acute stroke in salt-induced hypertension.

Investigations regarding hypertension and dietary sodium, both factors that influence stroke risk, have previously been limited to using genetically disparate treatment and control groups, namely the stroke-prone, spontaneously hypertensive rat and Wistar-Kyoto rat. In this investigation, we have characterized and compared cerebral vasoactive system adaptations following stroke in genetically identical, salt-induced hypertensive, and normotensive control mice. Briefly, ANP(+/-) (C57BJ/6 × SV129 background) mice were fed chow containing either 0.8% NaCl (NS) or 8.0% NaCl (HS) for 7 weeks. Transient cerebral ischemia was induced by middle cerebral artery occlusion (MCAO). Infarct volumes were measured 24-h post-reperfusion and the mRNA expression of five major vasoactive systems was characterized using qPCR. Along with previous publications, our data validate a salt-induced hypertensive state in ANP(+/-) mice fed HS chow as they displayed left ventricular hypertrophy, increased systolic blood pressure, and increased urinary sodium excretion. Following MCAO, mice fed HS exhibited larger infarct volumes than their dietary counterparts. In addition, significant up-regulation in Et-1 and Nos3 mRNA expression in response to salt and stroke suggests implications with increased cerebral damage in this group. In conclusion, our data demonstrate increased cerebral susceptibility to stroke in salt-induced hypertensive mice. More importantly, however, we have characterized a novel method of investigating hypertension and stroke with the use of genetically identical treatment and control groups. This is the first investigation in which genetic confounding variables have been eliminated.

Contralateral hyperacute intracerebral hemorrhage after carotid artery stenting with contralateral internal carotid artery occlusion.

An 87-year-old man sustained an intracerebral hemorrhage in the watershed area of the contralateral frontal lobe immediately after carotid artery stenting (CAS) for severe cervical internal carotid artery (ICA) stenosis. The contralateral cervical ICA was occluded. CAS resulted in increased cross-flow through the anterior communicating artery and increased flow in the contralateral middle cerebral artery. This case demonstrates that CAS in patients with contralateral ICA occlusion and insufficient collateral flow can cause dramatically increased collateral flow through the circle of Willis and result in contralateral hyperperfusion. In patients with severely compromised cerebral perfusion, measures should be taken to prevent hyperperfusion-related complications.

The role of Willis circle variations during unilateral selective cerebral perfusion: a study of 500 circles.

OBJECTIVES: During unilateral selective cerebral perfusion (uSCP), with right axillary artery or brachiocephalic trunk cannulation, the brain receives blood only via the right common carotid artery and right vertebral artery (VA). The left hemisphere is perfused mainly through the circle of Willis (CW). However, at least 50% of individuals have some variation in the CW. The aim of the present work was to study the variations in CW and VA that could have an impact on haemodynamics during uSCP. METHODS: From May 2005 to March 2012, a total number of 250 circles obtained via routine dissection for medico-legal reasons were examined. The external diameters of all CW segments and both VAs were measured. From January 2008 to March 2012, a total number of 250 patients subjected to computed tomographic angiography of the CW were also examined. RESULTS: Nine evident configurations of the CW that could cause hypoperfusion during uSCP were observed. They were subdivided in to seven types, according to location and the number of major vessels at risk of hypoperfusion. Type IA: hypo/aplasia of left posterior communicating artery (PComA), found in 35.6% of cases; Type IB: hypo/aplasia of anterior communicating artery (AComA), found in 2% of cases; Type IIA: hypo/aplasia of both left PComA and AComA, found in 4.8% of cases; Type IIB: hypo/aplasia of precommunicating (P1) segment of left posterior cerebral artery or right VA, found in 9.2% of cases; Type IIIA: hypo/aplasia of precommunicating (A1) segment of right anterior cerebral artery, found in 6% of cases; Type IIIB: hypo/aplasia of both right VA and AComA, found in 0.2% of cases; Type IV: hypo/aplasia of both right A1 and right VA or both right A1 and left P1, found in 0.8% of cases. All types were present in 58.6% of all examined CWs. CONCLUSIONS: Our results show that CW variations are present in a significant number of patients. Our data support the need for extensive preoperative examination and meticulous intraoperative monitoring of cerebral perfusion during uSCP. Finally, our data support the superiority of bilateral SCP over uSCP, because most of the variations reported do not have haemodynamic significance during bilateral SCP.

Contralateral microemboli following carotid artery stenting in patients with a contralateral internal carotid artery occlusion.

Subclinical microembolization identified on diffusion-weighted magnetic resonance imaging is recognized as an important outcome measure for carotid revascularization procedures. It is generally believed that arch manipulation is the primary reason for developing microemboli in the contralateral hemisphere during carotid artery stenting. However, we identified three patients who developed postprocedure microemboli of the contralateral hemisphere despite a known chronic contralateral internal carotid artery occlusion. Our cases highlight that ipsilateral microemboli may be an underappreciated but an important source of contralateral lesions through patent intracranial collateral pathways.

Status of the circle of Willis and intolerance to carotid cross-clamping during carotid endarterectomy.

PURPOSE: During carotid endarterectomy (CEA), an intolerance to the cross-clamping (CC) can occur. The purpose of this study was to evaluate whether preoperative magnetic resonance angiography (MRA) can predict CC intolerance. MATERIAL AND METHODS: Seventy-one patients (57 males, 14 females, mean age 71.8 years, age range 46-86 years) underwent 71 CEA procedures under local anaesthesia. Before CEA, patients underwent an MRA of the Circle of Willis (CoW) and were then classified into three groups: group A consisted of patients with a complete CoW, group B included patients with one agenesia/obstruction in the CoW and group C comprised patients with two or more agenesiae/obstructions in the CoW. The association between the number of anatomical variants in the CoW, corrected for the status of the contralateral carotid artery, and the onset of CC intolerance was evaluated. RESULTS: The prevalence of intolerance to CC was 15.5% (11/71). The Fisher test and logistic regression analysis showed a statistically significant association between the intolerance to CC and two or more agenesiae/obstructions in the CoW (p value < 0.00001 and p < 0.001, respectively). No neurological complications were observed. CONCLUSION: The results of our study showed that two or more agenesiae/obstructions of the CoW identified by MRA were associated with a high risk of intolerance to CC during CEA.

Focal cerebral ischemia after surgery in the "beach chair" position: the role of a congenital variation of circle of Willis anatomy.

A 50-year-old man underwent shoulder surgery in the beach chair position. His mean arterial blood pressure at arm level was approximately 65 mm Hg. Postoperatively, there was delayed awakening and a right hemiparesis. Radiologic evaluation revealed a congenital asymmetry of the circle of Willis that resulted in limited collateral flow to the left anterior and middle cerebral artery distributions. Similar anatomical variations are relatively common in the general population and may render some patients relatively and unpredictably more vulnerable to hypotension.

Intracranial collateralization determines hemodynamic forces for carotid plaque disruption.

INTRODUCTION: Percent diameter reduction provides an imperfect assessment of the risk for stroke from carotid atheroembolism. Stroke associated with atherosclerotic carotid stenosis commonly results from plaque disruption brought about by hemodynamic shear stress and Bernoulli forces. The aim of the present study was to predict the effect of incomplete intracranial collateralization through the circle of Willis (COW) on disruptive hemodynamic forces acting on carotid plaques. METHODS: A simple circuit model of the major pathways and collaterals that form and supply the COW was developed. We modeled the intra- and extracranial arterial circuits from standard anatomic references, and the pressure-flow relationships within these conduits from standard fluid mechanics. The pressure drop caused by (laminar and turbulent) flow along the internal carotid artery path was then computed. Carotid circulation to the brain was classified as being with or without collateral connections through the COW, and the extracranial carotid circuit as being with or without severe stenosis. The pressure drop was computed for each scenario. Finally, a linear circuit model was used to compute brain blood flow in the presence/absence of a disconnected COW. RESULTS: Pressure drop across a carotid artery stenosis increased as the flow rate within the carotid conduit increased. Poststenotic turbulence from a sudden expansion distal to the stenosis resulted in an additional pressure drop. Despite the stenosis, mean brain blood flow was sustained at 4.15 mL/s bilaterally. In the presence of an intact (collateralized) COW, this was achieved by enhanced flow in the contralateral (normal) carotid artery. However, in a disconnected COW, this was achieved by sustained systolic and enhanced diastolic flow through the stenosed artery. For a similar degree of stenosis, flow and velocity across the plaque was much higher when the COW was disconnected compared with an intact COW. Furthermore, the pressure drop across a similar stenosis was significantly higher with a disconnected COW compared with an intact COW. CONCLUSIONS: Incomplete intracranial collateralization through the COW results in increased flow rates and velocities, and therefore large pressure drops across a carotid artery stenosis. This exerts large disruptive shear stress on the plaque compared with patients with an intact COW. Percent diameter reduction provides an inaccurate assessment of risk for atheroembolic stroke. An assessment of carotid flow rates, flow velocities, and the intracranial collateral circulation may add independent information to refine the estimation of stroke risk in patients with asymptomatic carotid atherosclerosis.

True aneurysms of the posterior communicating artery: a systematic review and meta-analysis of individual patient data.

OBJECTIVE: To review and analyze systematically the reported cases of "true" posterior communicating artery (PCoA) aneurysm. METHODS: A retrospective review of the published literature was performed, and a meta-analysis of individual patient data was conducted. RESULTS: Pooled data showed that "true" PCoA aneurysms represent about 1.3% (95% confidence interval [CI] 0.8%, 1.7%) of all intracranial aneurysms and 6.8% (95% CI 4.3%, 9.2%) of all PCoA aneurysms. Mean patient age was 53.5 years (53.5 years ± 15.4), and age range was 23-79 years. Of the 49 patients reported in the literature, 44 (89.8%) were reported as ruptured, and 4 (10.2%) were reported as unruptured. There were no significant differences in ruptured status between age (P = 0.321), left vs right aneurysm (P = 0.537), and shape of aneurysm (P = 0.408). No significant differences in complication rates were found between rupture status (P = 0.27), and operative modalities (P = 0.878). The mean ages of patients who had no complications and patients who had complications were 53 years (53 years ± 2.59) vs 53.2 years (53.2 years ± 5.02) (P = 0.972). CONCLUSIONS: "True" PCoA aneurysms represent about 1.3% of all intracranial aneurysms and 6.8% of all PCoA aneurysms. They are more prone to rupture compared with their counterpart junctional aneurysms. When surgical management is indicated, a good understanding of the location and configuration of the aneurysm neck before surgical treatment is critical in the successful treatment of these lesions.

Transcranial duplex sonography for monitoring circle of Willis artery occlusion in a rat embolic stroke model.

BACKGROUND: Hemodynamic monitoring of circle of Willis arteries during clot embolization in experimental embolic stroke models (ES) is of major importance to assess their reproducibility and to test new recanalization strategies. We sought to assess the potential of transcranial duplex sonography (TDS) in comparison with laser Doppler flowmetry (LDF) to monitor the time of recanalization after occlusion of the right distal intracranial internal carotid artery (rICA) and to predict infarct volume at 24h after ischemia. METHODS: Twenty nine male Sprague-Dawley rats were submitted to ES. Right and left ICA, posterior cerebral arteries, and basilar trunk (BT) were monitored by TDS and regional cerebral blood flow was monitored by LDF at baseline, 1, 4 and 24h after the ES onset. Infarct volume was measured at 24h after stroke. RESULTS: Among the 25 rats, 3 died during surgery, 5 did not show any significant brain infarct (failure of the stroke model) and absence of occlusion of the rICA was detected in all 5 rats by TDS at 1h whereas only 4 of 5 were detected by LDF. Among the remaining 17 rats, the recanalization time of the occluded rICA assessed by TDS correlated with the infarct volume at 24h, r=0.70, P=0.0013 by contrast to results with LDF, r=0.11, P=0.55. CONCLUSION: Although both TDS and LDF can be used for in vivo assessment of occlusion in a rat ES model, TDS was more reliable as it allowed more accurate monitoring of arterial recanalization, and prediction of infarct volume.

Recovery of third nerve palsy following surgical clipping of posterior communicating artery aneurysms.

BACKGROUND: The objective of the study was to identify the predictors of improved third cranial nerve (CN III) function in patients who underwent surgical clipping for posterior communicating artery (PComA) aneurysms with varying degrees of CN III palsy at presentation. METHODS: We retrospectively evaluated the outcome of the CN III function in a series of 26 patients with CN III dysfunction due to PComA aneurysms that were treated by surgical clipping. RESULTS: CN III palsy was complete in 18 patients (69%) and partial in 8 patients (31%) at the time of admission. In 15 patients (58%), there was total improvement of CN III function. Partial improvement was noted in 5 patients (19%). Overall improvement (partial and total) of CN III function was observed in 20 (77%) of the 26 patients. The improvement in CN III function following early surgery (0-3 days) was 81.3% when compared to 75% when surgery was performed after 3 days. In univariate analysis, the only variable showing significant association with total improvement of CN III function was type of third nerve palsy at admission (complete vs partial) (P=.004). There was no statistical significant association between early surgery and improvement of CN III function (P=.722). In multivariate analysis, among all the factors, the type of third nerve palsy at presentation (complete and partial) was the significant predictor of the improved CN III function (P=.0038). CONCLUSION: Surgical clipping of the PComA aneurysm in patients with CN III palsy results in improvement of the CN III function in the majority of patients. The type of the CN III palsy at admission (complete/partial) is a significant predictor of complete improvement in CN III function.