Interrelations of Cerebral Hemodynamics with Parameters of Cardiac Function and Brain Tissue in Patients with Ischemic Stroke.

We analyzed interrelations between the cerebral blood flow, cardiac output, and condition of the brain substance in 530 patients with ischemic stroke. Dependencies between the linear blood flow velocities in all arteries supplying the brain, as well as between the total volume blood flow through the internal carotid arteries and left ventricular stroke volume were revealed. The severity of atrophy was maximum in the parietal lobes (median 1.5 (1.0; 2.0)) and minimum in the occipital lobes (median 0.5 (0; 1.0)). Temporal lobes cortical atrophy significantly correlated with changes in the limbic system and in the periventricular and deep white matter; a significant weak inverse correlation of this parameter with blood flow in the middle cerebral artery was also found. Changes in the periventricular white matter (but not in deep white matter) demonstrated a significant inverse correlation with blood flow in the middle and anterior cerebral arteries.

Anterior Cerebral Artery Stroke: Role of Collateral Systems on Infarct Topography.

Background and Purpose: The circle of Willis (CoW) and leptomeningeal anastomoses play an important role in transforming infarct topography following middle cerebral artery occlusion. Their role in infarct topography following anterior cerebral artery occlusion is not well understood. The aim of this study was to evaluate the role of the CoW and leptomeningeal anastomoses in modifying regional variation in infarct topography following occlusion of the anterior cerebral artery and its branches. Methods: Perfusion and magnetic resonance imaging of patients with anterior cerebral artery stroke and evidence of vessel occlusion were segmented and manually registered to standard brain template for voxel-wise comparison. Next, a computer model of the cerebral arteries was formulated as network of nodes connected by cylindrical pipes. The experiments included occlusion of successive branches of the anterior cerebral artery while the configurations of the CoW were varied. Results: Forty-seven patients with a median age of 77.5 years (interquartile range, 68.0­84.5 years) were studied. The regions with the highest probabilities of infarction were the superior frontal gyrus (probability =0.26) and anterior cingulate gyrus (probability =0.24). The regions around the posterior cingulate gyrus (probability =0.08), paracentral lobule (probability =0.05), precuneus and superior parietal lobule (probability =0.03) had a low probability of infarction. Following occlusions distal to the anterior communicating artery, the computer model demonstrated an increase in flow (>30%) in neighboring cortical arteries with leptomeningeal anastomoses. Conclusions: Traditionally the CoW has been regarded as the primary collateral system. However, our computer model shows that the CoW is only helpful in redirecting flow following proximal vessel occlusions (pre-anterior communicating artery). More important are leptomeningeal anastomoses, which play an essential role in distal vessel occlusions, influencing motor outcome by modifying the posterolateral extent of infarct topography.

The slope of cerebral oxyhemoglobin oscillation is associated with vascular reserve capacity in large artery steno-occlusion.

Inadequate cerebral perfusion is a risk factor for cerebral ischemia in patients with large artery steno-occlusion. We investigated whether prefrontal oxyhemoglobin oscillation (ΔHbO2, 0.6-2 Hz) was associated with decreased vascular reserve in patients with steno-occlusion in the large anterior circulation arteries. Thirty-six patients with steno-occlusion in the anterior circulation arteries (anterior cerebral artery, middle cerebral artery, and internal carotid artery) were included and compared to thirty-six control subjects. Patients were categorized into two groups (deteriorated vascular reserve vs. preserved vascular reserve) based on the results of Diamox single- photon emission computed tomography imaging. HbO2 data were collected using functional near-infrared spectroscopy. The slope of ΔHbO2 and the ipsilateral/contralateral slope ratio of ΔHbO2 were analyzed. Among the included patients (n = 36), 25 (69.4%) had deteriorated vascular reserve. Patients with deteriorated vascular reserve had a significantly higher average slope of ΔHbO2 on the ipsilateral side (5.01 ± 2.14) and a higher ipsilateral/contralateral ratio (1.44 ± 0.62) compared to those with preserved vascular reserve (3.17 ± 1.36, P = 0.014; 0.93 ± 0.33, P = 0.016, respectively) or the controls (3.82 ± 1.69, P = 0.019; 0.94 ± 0.29, P = 0.001). The ipsilateral/contralateral ΔHbO2 ratio could be used as a surrogate for vascular reserve in patients with severe steno-occlusion in the anterior circulation arteries.

Traumatic Distal Anterior Cerebral Artery Aneurysms - Pathomechanism and Revascularisation Strategies.

Traumatic intracranial aneurysms (TICA) of the distal anterior cerebral artery (dACA) are exceptionally rare and display therapeutic challenges due to their angioanatomical characteristics. The objective of this work was to discuss the mechanisms of TICA formation of the dACA and to elucidate the best treatment and revascularization strategies in these patients based on two illustrative cases. Case 1: 20-year-old patient with a traumatic, partially thrombosed 14 × 10 mm aneurysm of the right pericallosal artery (rPericA), distal to the origin of the right callosomarginal artery (rCMA). Complete trapping of the right dissection A3 aneurysm and flow replacement extra-to-intracranial (EC-IC) bypass (STA - radial artery - A4) was performed. Case 2: 16-year-old patient with a traumatic polylobulated, partially thrombosed 16 × 10 mm aneurysm of the rPericA. Microsurgical excision of the A3- segment harboring the aneurysm and flow replacement intra-to-intracranial (IC-IC) bypass via reimplantation of the right remaining PericA on the contralateral PericA (end-to-side anastomosis) was performed (in situ bypass). TICA of the dACA are exceptionally rare. Mechanical vessel wall injury and aneurysm formation of the dACA in blunt head trauma is very likely due to the proximity of the dACA with the rigid free edge of the falx. Given their nature as dissecting (complex) aneurysm, trapping and revascularization is a very important strategy. The interhemispheric cistern offers multiple revascularization options with its numerous donor vessels. The IC-IC bypass is often the simplest revascularization construct.

Specific clinical features and one-stage revascularization surgery for moyamoya disease with severe cerebral ischemia in the territory of posterior cerebral artery.

BACKGROUND: There are no reports describing the surgical procedure for moyamoya disease (MMD) patients with severe cerebral ischemia in the territory of the posterior cerebral artery (PCA) at initial presentation. In this study, therefore, we describe their clinical and radiological features and clinical results of one-stage revascularization surgery for both anterior and posterior circulation. METHODS: This study included 6 MMD patients who had severe cerebral ischemia in the PCA territory and underwent one-stage revascularization surgery for both anterior and posterior circulation. Of these, one patient underwent it on both sides. Their clinical and radiological data were precisely analyzed. Compared with usual procedure, craniotomy was extended towards the temporo-parietal area more widely. The parietal branch of superficial temporal artery (STA) was anastomosed to the angular or posterior temporal artery, while the frontal branch was anastomosed to the frontal branch of MCA. Ultimate indirect bypass was added. Their clinical and radiological outcomes were evaluated. RESULTS: Their neurological symptoms included visual and speech disturbance as well as numbness of the extremities. Cerebral infarct was distributed in the posterior temporal, parietal, and/or occipital lobe. Cerebral hemodynamics and metabolism were also impaired in the same regions. These findings were completely different from those in MMD patients without PCA lesion. Postoperative course was uneventful, and none of them recurred stroke during a mean follow-up period of 10.5 years. Surgical collaterals widely provided blood flow to the entire hemispheres, including the occipital lobe. Cerebral hemodynamics and metabolism markedly improved after surgery. CONCLUSION: One-stage revascularization surgery for both anterior and posterior circulation is feasible and effective to prevent future stroke in MMD patients with severe cerebral ischemia in the PCA territory at initial presentation.

A new index of ultrasonography for estimating cerebral circulation in newborn infants.

PURPOSE: To quantitatively estimate the influence of ductal shunt on cerebral blood flow and establish a new index of ultrasonography for estimating cerebral circulation without the influence of ductal shunt in newborn infants. METHODS: We retrospectively examined the records of anterior cerebral artery (ACA) and left pulmonary artery (LPA) blood flow velocity curves recorded by pulsed Doppler ultrasonography within 6 h after birth in 123 newborn infants without asphyxia (normal group) and in 31 newborn infants with asphyxia (asphyxia group). RESULTS: In the normal group, the resistance index (RI) of the ACA showed a positive correlation with the ratio of LPA diastolic-to-systolic flow velocities (LPAD/LPAS) (P < 0.001, r = 0.58), and the estimated RI (eRI) of the ACA was calculated using the following formula: Y = 0.47X + 0.67 (Y estimated RI; X LPAD/LPAS). In the asphyxia group, the RI of the ACA showed a weak correlation to base excess (BE) (P < 0.05, r = 0.46). The eRI of the ACA was calculated by the LPAD/PLAS in the asphyxia group, and the difference between the RI and eRI showed a better correlation to BE than RI (P < 0.001, r = 0.64). CONCLUSION: We determined the relation between cerebral blood flow RI and ductal shunt, and (RI - eRI) may be a new useful ultrasonographic index indicating cerebral circulation without the influence of ductal shunt in newborn infants.

Impaired Collateral Flow in Pial Arterioles of Aged Rats During Ischemic Stroke.

Cerebral collateral circulation and age are critical factors in determining outcome from acute ischemic stroke. Aging may lead to rarefaction of cerebral collaterals, and thereby accelerate ischemic injury by reducing penumbral blood flow. Dynamic changes in pial collaterals after onset of cerebral ischemia may vary with age but have not been extensively studied. Here, laser speckle contrast imaging (LSCI) and two-photon laser scanning microscopy (TPLSM) were combined to monitor cerebral pial collaterals between the anterior cerebral artery (ACA) and the middle cerebral artery (MCA) in young adult and aged male Sprague Dawley rats during distal middle cerebral artery occlusion (dMCAo). Histological analysis showed that aged rats had significantly greater volumes of ischemic damage than young rats. LSCI showed that cerebral collateral perfusion declined over time after stroke in aged and young rats, and that this decline was significantly greater in aged rats. TPLSM demonstrated that pial arterioles narrowed faster after dMCAo in aged rats compared to young adult rats. Notably, while arteriole vessel narrowing was comparable 4.5 h after ischemic onset in aged and young adult rats, red blood cell velocity was stable in young adults but declined over time in aged rats. Overall, red blood cell flux through pial arterioles was significantly reduced at all time-points after 90 min post-dMCAo in aged rats relative to young adult rats. Thus, collateral failure is more severe in aged rats with significantly impaired pial collateral dynamics (reduced diameter, red blood cell velocity, and red blood cell flux) relative to young adult rats.

Poor Outcomes Related to Anterior Extension of Large Hemispheric Infarction: Topographic Analysis of GAMES-RP Trial MRI Scans.

BACKGROUND: We aimed to assess the correlation of lesion location and clinical outcome in patients with large hemispheric infarction (LHI). METHODS: We analyzed admission MRI data from the GAMES-RP trial, which enrolled patients with anterior circulation infarct volumes of 82-300 cm3 within 10 hours of onset. Infarct lesions were segmented and co-registered onto MNI-152 brain space. Voxel-wise general linear models were applied to assess location-outcome correlations after correction for infarct volume as a co-variate. RESULTS: We included 83 patients with known 3-month modified Rankin scale (mRS). In voxel-wise analysis, there was significant correlation between admission infarct lesions involving the anterior cerebral artery (ACA) territory and its middle cerebral artery (MCA) border zone with both higher 3-month mRS and post-stroke day 3 and 7 National Institutes of Health Stroke Scale (NIHSS) total score and arm/leg subscores. Higher NIHSS total scores from admission through poststroke day 2 correlated with left MCA infarcts. In multivariate analysis, ACA territory infarct volume (P = .001) and admission NIHSS (P = .005) were independent predictors of 3-month mRS. Moreover, in a subgroup of 36 patients with infarct lesions involving right MCA-ACA border zone, intravenous (IV) glibenclamide (BIIB093; glyburide) treatment was the only independent predictor of 3-month mRS in multivariate regression analysis (P = .016). CONCLUSIONS: Anterior extension of LHI with involvement of ACA territory and ACA-MCA border zone is an independent predictor of poor functional outcome, likely due to impairment of arm/leg motor function. If confirmed in larger cohorts, infarct topology may potentially help triage LHI patients who may benefit from IV glibenclamide. CLINICAL TRIAL REGISTRATION: URL: https://www.clinicaltrials.gov. Unique identifier: NCT01794182.

Large Vessel Occlusion in Acute Ischemic Stroke Patients: A Dual-Center Estimate Based on a Broad Definition of Occlusion Site.

BACKGROUND: Accurate assessment of the frequency of large vessel occlusion (LVO) is important to determine needs for neurointerventionists and thrombectomy-capable stroke facilities. Current estimates vary from 13% to 52%, depending on acute ischemic stroke (AIS) definition and methods for AIS and LVO determination. We sought to estimate LVO prevalence among confirmed and suspected AIS patients at 2 comprehensive US stroke centers using a broad occlusion site definition: internal carotid artery (ICA), first and second segments of the middle cerebral artery (MCA M1,M2), the anterior cerebral artery, vertebral artery, basilar artery, or the proximal posterior cerebral artery. METHODS: We analyzed prospectively maintained stroke databases of patients presenting to the centers between January and December 2017. ICD-10 coding was used to determine the number of patients discharged with an AIS diagnosis. Computed tomography angiography (CTA) or magnetic resonance angiography (MRA) was reviewed to determine LVO presence and site. Percentages of patients with LVO among the confirmed AIS population were reported. RESULTS: Among 2245 patients with an AIS discharge diagnosis, 418 (18.6%:95% confidence interval [CI] 17.3%-20.0%) had LVO documented on CTA or MRA. Most common occlusion site was M1 (n=139 [33.3%]), followed by M2 (n=114 [27.3%]), ICA (n=69[16.5%]), and tandem ICA-MCA lesions (n=44 [10.5%]). Presentation National Institutes of Health Stroke Scale scores were significantly different for different occlusion sites (P=.02). CONCLUSIONS: The LVO prevalence in our large series of consecutive AIS patients was 18.6% (95% CI 17.3%-20.0%). Despite the use of a broad definition, this estimate is less than that reported in most previous studies.

The Frontal Bone Window for Transcranial Doppler Ultrasonography in Critically Ill Patients: Validation of a New Approach in the ICU.

BACKGROUND AND OBJECTIVE: The temporal bone window (TBW) for transcranial Doppler (TCD) often fails to insonate the anterior cerebral artery (ACA). The frontal bone window (FBW) has never been evaluated in intensive care units (ICU). The main objective was to determine the ability of the FBW to assess ACA velocities in critically ill patients. METHODS: A prospective study was conducted in two ICUs of the Montpellier University Hospital (France), between November 2014 and September 2016. Adult patients admitted to ICU for brain injury, with a Glasgow Coma Scale score ≤ 13, were enrolled within 3 days after admission. A first TCD examination was carried out bilaterally through the TBW and FBW by an intensivist expert in TCD, repeated by the same examiner, and 15 min later by an intensivist certified in TCD, designated as non-expert, blinded. The success of the FBW examinations was defined by the ability to measure the ACA velocities. Intra- and interobserver agreements were analyzed according to the Bland and Altman method. RESULTS: A total of 147 patients were analyzed. The FBW succeeded in insonating the ACA in 66 patients [45%, CI (37-53)], 45 bilaterally and 21 unilaterally. For 16 patients (11%), the FBW was the only way to measure ACA velocities. By combining the two techniques, the ACA success rate increased from 62% CI (54-70) to 73% CI (65-79) (P = 0.05). Intra- and interobserver mean biases and 95% limits of agreement for ACA systolic velocity measurements through the FBW were 1 (- 33 to 35) and 2 (- 34 to 38) cm s-1, respectively. For paired TBW and FBW measures of ACA velocities, mean biases (± SD) for ACA systolic, and mean and diastolic velocities were relatively close to zero, but negatives (- 7 ± 33, - 2 ± 19, - 1 ± 15 cm s-1, respectively), highlighting that ACA velocities were lower with the FBW (A2 segment) than TBW (A1 segment). The correlation coefficient for ACA systolic velocities measured by the FBW and TBW was R = 0.47, CI (0.28-0.62). No risk factors for failure of the FBW were identified. CONCLUSIONS: In ICU, the FBW was able to insonate the ACA in 45% of patients admitted for brain injury, without the use of contrast agents. The FBW could improve the detection of ACA vasospasms.

Bihemisphere Ischemia Due to a Unilateral Lesion: A Case Report.

Bihemispheric ischemic strokes secondary to unilateral vessel disease are uncommon. We present the case of a 70-year-old man with multiple acute/subacute bilateral infarcts. The patient was found to have stenosis of the left internal carotid artery secondary to herpes zoster ophthalmicus vasculopathy, with involvement of the left proximal middle and anterior cerebral arteries. Angiographic studies also revealed A1 segment aplasia of the right anterior cerebral artery (ACA), thus indicating dependence on the left-sided circulation for perfusion of the bilateral ACA vascular territory. This case illustrates how A1 segment aplasia, an anatomic variant of the circle of Willis detected by angiographic studies, can contribute to bilateral infarction in the ACA vascular territory.

Flow diversion covering the M1 origin as a last resort.

INTRODUCTION: Internal carotid artery termination (ICAT) and proximal A1 aneurysms can be challenging for open surgical clipping or endovascular coiling. Treatment with flow diversion covering the middle cerebral artery (MCA), an end vessel supplying a terminal circulation, has not been reported. METHODS: A prospective, Institutional Review Board-approved database was analysed for patients with pipeline embolisation device (PED) placement from the anterior cerebral artery (ACA) to the ICA during cerebral aneurysm treatment. RESULTS: Nine cases were identified, including five proximal A1, three posterior communicating artery and one ICAT aneurysm locations. Average aneurysm size was 8.3 mm (range 3-17), with 67% saccular and 78% right-sided. Primary indication for treatment was significant dome irregularity (44%), recurrence or enlargement (33%), underlying collagen vascular disorder (11%) and traumatic pseudoaneurysm (11%). Preservation of the ipsilateral ACA (with PED placed in A1) was performed when the anterior communicating artery (67%) or contralateral A1 (33%) were absent on angiography. Adjunctive coiling was done in four cases (44%). There was one major stroke leading to mortality (11%) and one minor stroke (11%). Clinical follow-up was 27 months on average. Follow-up digital subtraction angiography (average interval 15 months) showed complete aneurysm obliteration (88%) or dome occlusion with entry remnant (12%). The jailed MCA showed minimal or mild delay (primarily anterograde flow) in 75% of cases and significant delay (reliance primarily on ACA and external carotid artery collaterals) in 25%. CONCLUSIONS: Covering the MCA with a flow diverting stent should be reserved for select rare cases. Strict attention to blood pressure augmentation during the periprocedural period is necessary to minimise potential ischaemic compromise.

A1 asynchrony, a potential risk factor for the rupture of anterior communicating artery aneurysms: A computational fluid dynamics study.

INTRODUCTION AND OBJECTIVES: The anterior communicating complex is one the most common locations for aneurysm development. It receives blood from both carotid circulations and the effect of synchrony on the arrival of blood flow has not been previously studied. The objective of this study was to compare the asynchrony conditions of the A1 pulse and its effects on the haemodynamic conditions of anterior communicating artery (ACoA) aneurysms. MATERIALS AND METHODS: From 2008 to 2017, 54 anterior communicating artery aneurysms treated at our centre were included in the study. Computational fluid dynamics (CFD) techniques were employed and simulations consisted of complete conditions of synchrony and introducing a delay of 0.2s in the non-dominant A1 artery. Time-averaged wall shear stress (TAWSS), low shear area (LSA), A1 diameter and ACoA angles were measured. RESULTS: The difference in the LSA in conditions of synchrony and asynchrony resulted in a broad range of positive and negative values. The symmetry index (p=0.04) and A1/A2 angle on the dominant artery (p=0.04) were associated with changes in LSA. CONCLUSIONS: In asynchrony, LSA increased in the absence of A1 asymmetry and low A1/A2 angles, potentially increasing the risk of aneurysm rupture in this location.

Influence of vessel morphology and variations on technical and clinical success in mechanical thrombectomy: -In vivo and in vitro analyses.

PURPOSE: To determine the impact of vessel variation and anatomical features on technical and clinical success. MATERIALS AND METHODS: In vitro blood clots (n=100) were introduced into a silicon carotid-T flow model of 2, 3 or 4mm. The ICA/M1angle varied at 45°, 90°, 135° and 180°. Peripheral embolism was measured. In vivo 50 pat. (73.5 yrs.,±15) with MCA occlusion were examined for siphon variation, ICA morphology, vessel diameter and angles. The patients were divided according to the clinical success (mRS): group A: mRS≤2 after 90 day and group B: mRS≥3. Furthermore the technical success (TICI) and number of retrieval (n) were analysed. RESULTS: In vitro with larger vessel diameter the migrated thrombus load decreased (P=.001). The steeper the M1/ICA angles, the higher thrombus weighs (180°: 2.94mg; 135°: 6.32mg; 90°: 8.65mg, 45°: 10.69mg; P<.001). In vivo patients with mRS≤2 had significantly lower NIHSS (16.5 vs 20, P=.009) and higher ASPECTS (9 vs 6, P<.05). TICI≥2b was more often achieved (86.6 vs 40% P=.002). The procedure time was lower (45 vs. 80min, P<.05) with smaller number of retrieval (1.5 vs 4, P<05). Proximal ICA stenosis offers a trend to unfavourable outcome (P=.073). Siphon variation "D" is associated with less retrieval manoeuvre. CONCLUSION: While in vitro there is a close correlation between embolism and vascular anatomy, in vivo carotid artery stenosis and siphon variation influence clinical and technical success.

Hemodynamic Fate of the Precommunicating Anterior Cerebral Artery Is Predicted by Vessel Dominance After Pipeline Embolization Device Deployment Across the Internal Carotid Artery Terminus.

BACKGROUND: The Pipeline embolization device (PED) is commonly used for the treatment of distal internal carotid artery (ICA) aneurysms, which often require placing the stent across the origin of the precommunicating segment of the anterior cerebral artery (ACA-A1). We sought to characterize the clinical and angiographic consequences of this maneuver. METHODS: We performed a retrospective review of a prospectively collected database of patients treated with the PED at a single academic center from 2011 to 2017 to find patients for whom the PED was extended across the origin of the ACA-A1. The patient demographic data, pretreatment angiographic imaging findings, sizing of the bilateral A1 and ipsilateral M1 segment of the middle cerebral artery (MCA-M1), and follow-up angiographic and clinical imaging findings were recorded. RESULTS: A total of 27 patients were included in the present study (8 men and 19 women; age, 52 ± 14.9 years). Follow-up angiography was conducted at a median of 9.2 months (interquartile range, 6; range, 5-84). The covered A1 segment was patent in 17 patients (63%). The covered ACA-A1/ipsilateral MCA-M1 ratio was 1.43 times greater for the patent ACA-A1 segments than those that were occluded (P = 0.0006). Similarly, the covered ACA-A1/contralateral ACA-A1 ratio was significantly larger statistically (1.64; P < 0.0001) for the patent ACA-A1 segments than that for those that were occluded. None of the patients developed clinical or radiographic signs of ACA stroke. The modified Rankin scale worsened for 1 patient during follow-up owing to a further decline of presenting vision loss. CONCLUSIONS: The PED can be used to treat aneurysms with deployment from the MCA-M1 to the ICA without resulting in ACA stroke. Ipsilateral A1 segment dominance might be predictive of continued blood flow into the ACA after deployment at this location.

The role of wall shear stress in the parent artery as an independent variable in the formation status of anterior communicating artery aneurysms.

OBJECTIVES: The study aimed to determine which hemodynamic parameters independently characterize anterior communicating artery (AcomA) aneurysm formation and explore the threshold of wall shear stress (WSS) of the parent artery to better illustrate the correlation between the magnitude of WSS and AcomA aneurysm formation. METHODS: Eighty-one patients with AcomA aneurysms and 118 patients without intracranial aneurysms (control population), as confirmed by digital subtraction angiography (DSA) from January 2014 to May 2017, were included in this cross-sectional study. Three-dimensional-DSA was performed to evaluate the morphologic characteristics of AcomA aneurysms. Local hemodynamic parameters were obtained using transcranial color-coded duplex (TCCD). Multivariate logistic regression and a two-piecewise linear regression model were used to determine which hemodynamic parameters are independent predictors of AcomA aneurysm formation and identify the threshold effect of WSS of the parent artery with respect to AcomA aneurysm formation. RESULTS: Univariate analyses showed that the WSS (p < 0.0001), angle between the A1 and A2 segments of the anterior cerebral artery (ACA) (p < 0.001), hypertension (grade II) (p = 0.007), fasting blood glucose (FBG; > 6.0 mmol/L) (p = 0.005), and dominant A1 (p < 0.001) were the significant parameters. Multivariate analyses showed a significant association between WSS of the parent artery and AcomA aneurysm formation (p = 0.0001). WSS of the parent artery (7.8-12.3 dyne/cm2) had a significant association between WSS and aneurysm formation (HR 2.0, 95% CI 1.3-2.8, p < 0.001). CONCLUSIONS: WSS ranging between 7.8 and 12.3 dyne/cm2 independently characterizes AcomA aneurysm formation. With each additional unit of WSS, there was a one-fold increase in the risk of AcomA aneurysm formation. KEY POINTS: • Multivariate analyses and a two-piecewise linear regression model were used to evaluate the risk factors for AcomA aneurysm formation and the threshold effect of WSS on AcomA aneurysm formation. • WSS ranging between 7.8 and 12.3 dyne/cm 2 was shown to be a reliable hemodynamic parameter in the formation of AcomA aneurysms. The probability of AcomA aneurysm formation increased one-fold for each additional unit of WSS. • An ultrasound-based TCCD technique is a simple and accessible noninvasive method for detecting WSS in vivo; thus, it can be applied as a screening tool for evaluating the probability of aneurysm formation in primary care facilities and community hospitals because of the relatively low resource intensity.

The Optimality Principle Decreases Hemodynamic Stresses for Aneurysm Initiation at Anterior Cerebral Artery Bifurcations.

OBJECTIVE: To investigate hemodynamic stresses on anterior cerebral artery bifurcation apex and possible mechanism of the optimality principle in protecting bifurcation wall from supercharged hemodynamic stresses. METHODS: Three-dimensional angiographic datasets of 122 patients with anterior communicating artery (Acom) aneurysms, 21 patients with non-Acom aneurysms, and 220 control subjects with no aneurysms were used. Radii of parent (r0) and daughter branches (r1 and r2) were measured, and bifurcations obeying the optimality principle required optimal caliber control of r0n = r1n + r2n, with the junction exponent n approximating 3. Radius ratio = r03/(r13 + r23) and n were compared between aneurysmal and control bifurcations. Blood flow was simulated for analysis of hemodynamic stresses. RESULTS: Acom bifurcations in subjects without Acom aneurysms displayed optimal caliber radius, with mean radius ratio of 0.99 and n of 3.25, whereas Acom aneurysmal bifurcations had significantly lower radius ratio, 0.62 (P < 0.05), but higher n, 4.23 (P < 0.05). Peak wall shear stress and corresponding total pressure were significantly smaller for bifurcations obeying than disobeying the optimality principle (P < 0.001 and P < 0.05, respectively). Total pressures in the direct impinging center, peak wall shear stress distance, and anterior cerebral artery bifurcation angle all were significantly smaller for bifurcations obeying than disobeying the optimality principle (P < 0.05 and P < 0.001, respectively). CONCLUSIONS: Normal anterior cerebral artery bifurcations obey the optimality principle whereas bifurcations with Acom aneurysms do not. Disobeying the optimality principle presents significantly enhanced hemodynamic stresses to possibly damage the bifurcation wall for aneurysm initiation.

Persistent Primitive Olfactory Artery as Novel Collateral Channel to the Anterior Cerebral Artery in Moyamoya Disease.

BACKGROUND: There are a variety of collateral routes to compensate persistent cerebral ischemia in moyamoya disease. However, there is no report presenting the persistent primitive olfactory artery (POA) as a spontaneous collateral route to the anterior cerebral artery (ACA) in moyamoya disease. METHODS: We precisely examined cerebral angiography in 84 patients with moyamoya disease to identify the collateral channel through the persistent POA. Its anatomy was evaluated on pre- and postoperative angiography. RESULTS: Of 84 patients, four (4.8%) had spontaneous collateral channel through the persistent POA. All of these four hemispheres were categorized into Stage 5. In all four patients, the collateral blood flow arose from the ophthalmic artery and run to the persistent POA through the ethmoidal moyamoya. The persistent POA provided collateral blood flow from the ophthalmic artery to the ACA in all four patients. Superficial temporal artery to middle cerebral artery anastomosis and encephalo-duro-myo-arterio-pericranial synangiosis was performed in three of four patients. After surgery, the collateral channel through the persistent POA completely disappeared or markedly regressed, suggesting a significant improvement of cerebral hemodynamics in the territory of not only the MCA but also the ACA. CONCLUSION: The persistent POA can potentially provide collateral blood flow to the ACA in about 5% of patients with moyamoya disease, and should be recognized as a novel collateral channel in moyamoya disease. The persistent POA may be useful to evaluate therapeutic effects of surgical revascularization on the ACA territory.

Enlarged Anterior Cerebral Artery Bifurcation Angles May Induce Abnormally Enhanced Hemodynamic Stresses to Initiate Aneurysms.

OBJECTIVE: To investigate the relationship of anterior cerebral artery (ACA) bifurcation angles with hemodynamic stresses for aneurysm initiation. METHODS: Forty patients with or without anterior communicating artery aneurysms were enrolled, and 3 patients with ACA bifurcation angles of 169.0°, 136.9°, and 73.2°, respectively, were entered into computational fluid dynamics analysis for hemodynamic stresses. RESULTS: Larger bifurcation angles had a larger direct flow impinging zone and larger peak pressure area. In the direct flow impinging center, the total pressure was the highest, whereas the other stresses were the lowest. As blood flowed distally, the total pressure decreased rapidly, whereas all other parameters increased quickly to their peaks. The hemodynamic peak distance was decreased as the bifurcation angle became narrower. The total pressure summit and the peak hemodynamic stresses all decreased with the decrease of bifurcation angles. The distance between the hemodynamic peaks was the smallest at 73.2° compared with larger angles. A significant (P < 0.01) positive linear correlation existed in the ACA bifurcation angle with the distance between hemodynamic stress peaks or in the ACA branch diameter with the distance from the direct impinging center to the ipsilateral hemodynamic stress peak. The hemodynamic stresses on the aneurysm dome were significantly (P < 0.001) smaller than at the aneurysm initiation site. CONCLUSIONS: Larger bifurcation angles may lead to abnormally enhanced hemodynamic stresses, enlarged zones of direct flow impingement, and increased distance between hemodynamic stress peaks to damage the vascular wall for aneurysm initiation on the bifurcation apex wall.

[Proximal clipping of a large fusiform aneurysm of the A2 segment of the left anterior cerebral artery with awakening of the patient (a case report and literature review)]. / Proksimal'noe klipirovanie bol'shoi fuziformnoi anevrizmy A2 segmenta levoi perednei mozgovoi arterii s probuzhdeniem bol'noi (sluchai iz praktiki i obzor literatury).

Arterial aneurysms of the A2 segment are very rare (<1%) peripheral aneurysms of the anterior cerebral artery (ACA) territory. Usually, these are saccular aneurysms; there are single reports of fusiform aneurysms of this location. Surgical treatment of these aneurysms involves both microsurgical and endovascular interventions. In the presented case, we used deconstructive surgery (proximal clipping of the aneurysm) with intraoperative awakening of the patient, which verified sufficient collateral blood flow. In the case of focal deficit development, we planned to simultaneously perform an interarterial anastomosis between the A3 segments of the right and left ACAs.