Contralateral Anterior Cerebral Artery Research Articles

Super-selective Wada test for pre-surgical leg motor function assessment: A case report.

Wada test is well-known to assess lateralization of memory and language functions; however, super-selective Wada (ss-Wada) to evaluate motor leg function is rare. We present a ss-Wada test within the anterior cerebral artery (ACA) to assess the motor function of the leg. Retrospective chart review. Comprehensive phase-I/II surgical evaluation revealed an ictal focus around the left post-central gyrus with immediate involvement around the left para-central regions. To avoid potential right leg motor dysfunction with the surgery, the patient underwent a ss-Wada procedure. Angiography revealed bilateral ACAs were supplied by the left A1 segment. Super-selective microcatheter injection of amobarbital into the left ACA was performed to avoid cross-filling the contralateral ACA. The ss-Wada test confirmed no right leg motor impairment. Afterward, a craniotomy with direct cortical stimulation confirmed that the left-sided ictal/peri-ictal zone had no clear leg motor function. The patient underwent disconnection of that region and remained seizure-free at 10-month post-op follow-up without any motor or sensory deficits in the right limbs. This case demonstrates the proof of concept for ss-Wada in assessing lower extremity motor function. The ss-Wada procedure accurately predicted no motor deficits in the right leg, consistent with preserved motor function post-surgery.

Left anterior cerebral artery arising from a right internal carotid artery: a rare case of carotid-anterior cerebral artery anastomosis

Carotid-anterior cerebral artery anastomosis (carotid-ACA anastomosis) is described as infrequent vascular connections between the pre-ophthalmic segment of the internal carotid artery (ICA) and the A1 segment of the anterior cerebral artery (ACA). The embryological origin of these variant is still unclear and they are often associated to other vascular anomalies of the circle of Willis, as well as to the presence of aneurysms. Carotid-ACA anastomosis is often right-sided although left and bilateral cases have also been described. We report a rare case by MR angiography of a carotid-ACA anastomosis in which the abnormal vessel arises from the right ICA and takes an infraoptic course to join the A2 segment of the contralateral ACA, making this vascular anomaly function as a ‘left ACA with an origin at the right ICA’. The A1 segment of the left ACA is absent and both A2 segments of the ACAs present fenestration. To our knowledge, no similar cases have been reported in English literature so far.

Bihemispheric Right Anterior Cerebral Artery, Fenestrated Origin of the Left Pericallosal Artery, Fenestrated Basilar Artery, Double Right Posterior Cerebral Artery.

Anatomical variations of the cerebral vasculature are frequently encountered. The archived magnetic resonance angiogram of a 62-year-old male patient was studied anatomically on planar slices and 3-dimensional volume renderings. Numerous anatomical variants were found in that single case. In the vertebrobasilar system were found: the proximal basilar artery fenestration, with a unilateral origin from that fenestration of an anterior inferior cerebellar artery, and the unilateral origin of the superior cerebellar artery from the P1 segment of the main posterior cerebral artery (PCA). There were also unilateral variants of the right internal carotid artery (ICA): a subvariant of an accessory PCA leaving the ICA as a hyperplastic anterior choroidal artery and united to the main PCA by a short communicating branch, distinctive of the posterior communicating artery in that side (unilateral double PCA); a right bihemispheric anterior cerebral artery (ACA) but with complete agenesis of the contralateral A1 ACA segment; from the right ACA continued an anatomically normal ipsilateral A2 segment and a short transverse contralateral A2 that, in turn, sent off long pericallosal and callosomarginal arteries; and fenestrated origin of the left pericallosal artery. Therefore, an arterial variant in one of the main cerebral circulations could not exclude anatomical variants in the other cerebral circulatory beds.

Distribution of intraperitoneally administered deuterium-labeled water in aquaporin-4-knockout mouse brain after middle cerebral artery occlusion.

As the movement of water in the brain is known to be involved in neural activity and various brain pathologies, the ability to assess water dynamics in the brain will be important for the understanding of brain function and the diagnosis and treatment of brain diseases. Aquaporin-4 (AQP4) is a membrane channel protein that is highly expressed in brain astrocytes and is important for the movement of water molecules in the brain. In this study, we investigated the contribution of AQP4 to brain water dynamics by administering deuterium-labeled water (D2O) intraperitoneally to wild-type and AQP4 knockout (AQP4-ko) mice that had undergone surgical occlusion of the middle cerebral artery (MCA). Water dynamics in the infarct region and on either side of the anterior cerebral artery (ACA) was monitored with proton-density-weighted imaging (PDWI) performed on a 7T animal MRI. D2O caused a negative signal change quickly after administration. The AQP4-ko mice showed a delay of the time-to-minimum in both the contralateral and ipsilateral ACA regions compared to wild-type mice. Also, only the AQP4- ko mice showed a delay of the time-to-minimum in the ipsilateral ACA region compared to the contralateral side. In only the wild-type mice, the signal minimum in the ipsilateral ACA region was higher than that in the contralateral ACA region. In the infarct region, the signal attenuation was slower for the AQP4-ko mice in comparison to the wild-type mice. These results suggest that AQP4 loss affects water dynamics in the ACA region not only in the infarct region. Dynamic PDWI after D2O administration may be a useful tool for showing the effects of AQP4 in vivo.

Neuromonitoring Guided Vessel Identification in Iatrogenic Arterial Injury During Meningioma Resection

ABSTRACT Neuromonitoring is commonly used in neurosurgery and allows intraoperative assessment of functional pathways in the brain during surgery. Monitoring alerts can guide surgical decision making in real-time allowing surgeons to mitigate or avoid potential iatrogenic injury and subsequent postoperative neurologic sequelae that may result from cerebral ischemia or malperfusion. Here we present a case of a patient undergoing a right pterional craniotomy for the resection of a tumor which crosses midline with multimodal intraoperative neuromonitoring including somatosensory evoked potentials, transcranial motor evoked potentials, and visual evoked potentials. During the final portion of tumor resection, arterial bleeding was noted of unknown origin shortly followed by loss of right lower extremity motor evoked potential recordings. Motor evoked potential recordings in the right upper, and left upper and lower extremities were stable, as well as all somatosensory evoked potentials and visual evoked potentials. This distinct pattern of right lower extremity motor-evoked potential loss suggested compromise of the contralateral anterior cerebral artery and guided the surgeons to a rapid intervention. The patient awoke from surgery with moderate postoperative weakness in the affected limb that resolved to preoperative status by postoperative day 2, and back to normal strength prior to three-month follow-up. In this case the neuromonitoring data suggested compromise to the contralateral anterior cerebral artery which guided the surgeons to investigate and identify the site of vascular injury. The present case reinforces the utility of neuromonitoring in emergent surgical situations to guide surgical decision making.

One-Stage Revascularization to the Ipsilateral Middle Cerebral Artery and Contralateral Anterior Cerebral Artery Territories

Patients with multiple intracranial atherosclerotic stenoses often present with hemodynamic instability in 2 remote regions without a reciprocal vascular network. In this situation, revascularization to each region may be required. In this report, 2 patients who had coexisting unilateral middle cerebral artery (MCA) and contralateral anterior cerebral artery territory ischemia were treated by using ipsilateral superficial temporal artery (STA)-radial artery graft-contralateral A3 bypass and ipsilateral STA-MCA bypass in one stage. Postoperatively, the bypass conduit was well established, and the patients' hemodynamic instability was improved. In patients with severe hemodynamic instability in the remote unilateral MCA and contralateral anterior cerebral artery regions, as in our 2 cases, ipsilateral STA-MCA and ipsilateral STA-radial artery graft-contralateral A3 bypasses in one stage can be a treatment option.

Structural changes in the side branches and the circle of Willis following the use of flowdiverting stents.

This study aimed to evaluate the diameter and flow changes in the circle of Willis and side branches following the use of FDSs extending from the middle cerebral artery (MCA) to the internal carotid artery (ICA) for the treatment of aneurysms in the terminal segment of ICA, and the clinical results. This study was conducted in a single center between January 2012 and April 2018 in patients with the anterior choroidal artery (AChoA), the posterior communicating artery (PComA), and the ICA terminal segment aneurysms treated with the FDSs. The changes in aneurysm size, arterial structures covered by the FDSs, and changes in the diameter and flow in arteries forming the circle of Willis were retrospectively analyzed. Fourteen patients with a total of 25 aneurysms treated with FDSs extending from MCA to ICA were evaluated. The mean aneurysm fundus size was 5.14 mm (range 1.5-22 mm). Before treatment, the anterior communicating artery (AComA) was patent in all patients. Implanted FDSs covered the anterior cerebral artery (ACA) and AChoA in all patients (100%), nonhypoplasic PComA in two patients (14.28%), and the ophthalmic artery in nine (64.3%). The mean follow-up time was 36.78 ± 22.44 months. In follow-up, there was a decrease in the mean ipsilateral ACA A1 segment diameter from 1.99 ± 0.58 cm to 1.81 ± 0.31 cm (p = 0.01). The mean contralateral A1 segment diameter increased from 1.66 ± 0.48 cm to 1.93 ± 0.42 cm (p = 0.004). All aneurysms were totally occluded. If the AComA is patent, ipsilateral anterior circulation can be compensated through modifications in the contralateral ACA A1 segment in patients with ICA terminal segment aneurysms treated with FDSs extended from MCA to ICA and covering ACA. Although covering the anterior choroidal and lenticulostriate arteries by FDSs, ischemic complications may not occur frequently. Thus, this effective therapy can be applied more safely.

Effects of LI11 Acupuncture on CO2 reactivity in the anterior and middle cerebral arteries during hyperventilation-induced hypocapnia in normal subjects: A before and after study

Objectives: The LI11 (Quchi) acupuncture point has always been included in the Seven acupoints for stroke; however, additional LI11 acupuncture research is needed. In this study, the effect of LI11 acupuncture on cerebral blood flow of the anterior cerebral arteries (ACA) and middle cerebral arteries (MCA) was investigated.Method: This study included 10 healthy young male subjects. Cerebral blood flow velocity and cerebrovascular reactivity were measured using transcranial Doppler sonography. Changes in hyperventilation-induced carbon dioxide (CO2) reactivity and modified ACA and MCA blood flow velocity at 40 mmHg (CV40), blood pressure, and heart rate were observed before and after LI11 acupuncture treatment.Results: A statistically significant increase in contralateral anterior cerebral artery CO2 reactivity (p=0.036) and decrease in contralateral middle cerebral artery CV40 (p=0.047) were observed. No significant difference in mean blood pressure was shown. A statistically significant increase in heart rate occurred after LI11 acupuncture; however, it was not clinically significant as there were negligible changes in the heart rhythm.Conclusions: LI11 acupuncture treatment could improve cerebral blood flow velocity. These results might be explained by regulating endothelium-dependent vessel dilation in the anterior cerebral artery region.Trial registration: This trial has been registered with Clinical Research Information Service, a service of the Korea Centers for Disease Control and Prevention: KCT0004494 (retrospectively registered). https://cris.nih.go.kr/cris/search/search_result_st01.jsp?seq=15359

Informativity of blood flow distribution in the precerebral arteries for determining the hemodynamic significance of carotid stenosis

Introduction. Conventionally, hemodynamic significance of carotid stenosis is characterized with an increased peak systolic velocity up to 230 cm/s, which corresponds to 70 % carotid stenosis. This does not take into account changes of cerebral hemodynamics or collateral circulation, which can be determined by assessment of blood flow distribution in precerebral arteries. Aim – to evaluate blood flow redistribution in precerebral arteries in patients with critical carotid stenosis. Materials and methods. 40 patients (aged 49–80 y. o.) with critical carotid stenosis were studied (13 patients had 70–79 % stenosis, 11 patients – 80–89 %, and 16 patients – 90–99 % stenosis). Flow velocity index in precerebral arteries was determined with duplex scanning (Vivid e, USA), whereas linear blood flow velocity in intracranial arteries – with transcranial Doppler (MultiDop X, Germany). Results. In 60 % of patients, flow velocity index in ipsilateral carotid artery was reliably decreased (p<0.05). In 49 % of patients flow velocity index in contralateral carotid artery and blood flow velocity in contralateral anterior cerebral artery were reliably increased (p<0.05), as well as linear blood flow velocity in the contralateral anterior cerebral artery. Just in 39 % of patients flow velocity index in ipsilateral vertebral artery and linear blood flow velocity in ipsilateral posterior cerebral artery were increased (p<0.05). In 13 % of cases flow velocity index in the external carotid artery was increased (p<0.05). Conclusion. Thus, critical degree of carotid stenosis does not always indicate its hemodynamic significance. Flow velocity index distribution in precerebral arteries can be used as an additional criterion for assessing hemodynamic significance of carotid stenosis and, along with other indicators, should be taken into account when choosing treatment modality.

Comparison of Single and Dual Monitoring during Carotid Endarterectomy

We compared the rate of selective shunt and pattern of monitoring change between single and dual monitoring in patients undergoing carotid endarterectomy (CEA). A total of 121 patients underwent 128 consecutive CEA procedures. Excluding five procedures using internal shunts in a premeditated manner, we classified patients according to the monitoring: Group A (n = 72), patients with single somatosensory evoked potential (SSEP) monitoring; and Group B (n = 51), patients with dual SSEP and motor evoked potential (MEP). Among the 123 CEAs, an internal shunt was inserted in 12 procedures (9.8%) due to significant changes in monitoring (Group A 5.6%, Group B 15.7%, p = 0.07). The rate of shunt use was significantly higher in patients with the absence of contralateral proximal anterior cerebral artery (A1) on magnetic resonance angiography (MRA) than in patients with other types of MRA (p <0.001). Significant monitor changes were seen in 16 (12.5%) in both groups. In four of nine patients in Group B, SSEP and MEP changes were synchronized, and in the remaining five patients, a time lag was evident between SSEP and MEP changes. In conclusion, the rate of internal shunt use tended to be more frequent in patients with dual monitoring than in patients with single SSEP monitoring, but the difference was not significant. Contralateral A1 absence may predict the need for a shunt and care should be taken to monitor changes throughout the entire CEA procedure. Use of dual monitoring can capture ischemic changes due to the complementary relationship, and may reduce the rate of false-negative monitor changes during CEA.

Role of Doppler Ultrasound Analysis of Blood Flow Through the Ophthalmic and Intracranial Arteries in Predicting Neurologic Symptoms During Carotid Endarterectomy.

Carotid endarterectomy (CEA) is frequently performed under locoregional anesthesia. The intraoperative clamping of the internal carotid artery (ICA) leads to cerebral hypoperfusion, which may in some patients result in the development of neurologic symptoms (NS). The objective of our study was to investigate whether there is an association between the preoperative ultrasound (US) Doppler flow in the ophthalmic artery (OA) and intracranial artery and the occurrence of these intraoperative NS. We compared 50 patients with NS and 150 patients without NS during CEA. We analyzed their preoperative blood flow characteristics by Doppler US and their clinical and demographic characteristics. The contralateral ICA occlusion increased the likelihood of intraoperative NS (odds ratio [OR], 8.4; P < .001). Abnormal contralateral OA flow also increased the likelihood of NS (OR, 1.84; P < .001), whereas ipsilateral abnormal OA flow reduced it (OR, 0.73; P=.06). Increased flow in the ipsilateral anterior cerebral artery (ACA) increased the likelihood of NS (OR, 3.3), whereas reversed flow decreased it (OR, 0.1; P=.03). Inverse flow in the contralateral ACA increased the risk (OR, 5.4), whereas increased flow reduced it (OR, 0.2; P=.02). Male patients had a higher risk of NS (P=.09) as well as older patients (P=.05). Eight percent of the patients with NS developed a transient ischemic attack or stroke. Doppler US analysis of the OA and ACA in combination with analysis of ICA stenosis may be a promising predictor of NS during ICA clamping. This, in turn, may warn the patient and the surgeon of an increased risk during surgery.

Side-to-Side Bypass between Bilateral Distal Anterior Cerebral Arteries and Surgical Trapping of a Pseudoaneurysm from the Anterior Communicating Artery: Lessons Learnt

Background:Treatment options for a ruptured anterior communicating artery (ACoA) pseudoaneurysm are limited. In most cases trapping of the ACoA is the best treatment option. Occasionally, bypass surgery is warranted to ensure blood flow to the contralateral anterior cerebral artery (ACA) in cases with one dominant A1. We report a case of an ACoA pseudoaneurysm presenting with delayed subarachnoid hemorrhage following surgical clipping of an unruptured ACoA aneurysm, with a review of the literature.Case description:A 74-year-old female had undergone surgical clipping of a 1.2-cm-sized unruptured ACoA aneurysm through the left supraorbital keyhole approach. During the operation, there had been a small tear between the aneurysm neck and the right proximal A2, and the tear point was controlled by clipping of the tear site. One month later, she was admitted again because of subarachnoid hemorrhage. Cerebral angiography showed a probable pseudoaneurysm from the previous tear site. The patient had a dominant left A1 with a right A1 aplasia. The pseudoaneurysm was treated with side-to-side bypass between the distal ACAs and subsequent trapping of the ACoA harboring a pseudoaneurysm. Both the distal ACAs were preserved; however, post-hemorrhagic neurological sequelae remained.Conclusions:Side-to-side bypass between distal ACAs and surgical trapping of the ACoA for the ruptured ACoA pseudoaneurysm was a good rescue option to prevent rebleeding and preserve blood supply to the contralateral ACA territory.

Dissection of anterior cerebral artery presenting with cerebral infarction in contralateral frontal lobe

AbstractAlthough diagnosis of dissection in the anterior cerebral artery (ACA) has increased, cerebral infarction in frontal lobe due to contralateral ACA dissection is rare. A 52‐year‐old woman developed headache and motor weakness in the left hemibody. Magnetic resonance images demonstrated a fresh cerebral infarction in the right frontal lobe and thin right ACA. The initial diagnosis was a cerebral infarction in the right frontal lobe due to right ACA stenosis. Angiography performed nine days after onset showed dilatation and stenosis of the left ACA, and a small diameter of the right ACA. An intramural thrombus in the left ACA was demonstrated on MRI. The diagnosis was a cerebral infarction in the right frontal lobe due to dissection of the contralateral left A2 and A3 of ACA. There is a possibility that cerebral infarction in frontal lobe is induced by the contralateral ACA abnormality in a case with bihemispheric ACA.

Moyamoya Syndrome with contra lateral DACA aneurysm: First Case report with review of literature

Abstract Moyamoya disease is a progressive steno-occlusive disease of bilateral internal carotid artery with the development of fine collateral vessels and is an angiographic diagnosis. Concurrent Moyamoya disease with intracranial aneurysm had been reported in literature by various authors. Moyamoya disease is reported with aneurysm at various locations including basilar tip, anterior choroidal artery, posterior choroidal artery, anterior cerebral artery and middle cerebral artery. After reviewing literature thoroughly there is not a single case report on Moyamoya disease with isolated distal anterior cerebral artery aneurysm with the best of our knowledge. Here we are reporting a case of Moyamoya disease of left petrous and cavernous part of internal carotid artery with contralateral distal anterior cerebral artery aneurysm in a 36-year-old male.

Flow diversion within seven days after stroke onset is associated with favorable outcome in anterior circulation stroke

Anterior cerebral artery (ACA) flow diversion (FD), defined as ipsilateral mean velocity (MV) of at least 30% greater than the contralateral artery, could be seen an indirect sign of leptomeningeal collateralization in the setting of middle cerebral artery occlusion. The purpose of the study was to evaluate the association between dynamic FD and functional outcome in acute anterior stroke patients with large artery occlusion. Acute middle cerebral artery (MCA) or internal carotid artery (ICA) occlusive stroke patients within 12h were recruited. Transcranial Doppler ultrasound was done at baseline, 24h and 7d after onset and velocities of MCA and ACA were recorded. FD ratio was calculated by dividing the ipsilateral ACA MV by the contralateral ACA MV. FD was determined positive when FD ratio ≥1.3. Outcome was assessed by 90-day modified Rankin’s Scale (mRS). The association between FD at different time points and functional outcome were analyzed. 16 patients (median age of 67 and 75% were male) were recruited. FD ratio showed a trend of decline but did not reach statistical significance (p=0.056). The proportion of FD at baseline (p=0.026), 24h (p=0.001) and 7d (p=0.044) was significantly higher in patients with favorable outcome. Higher FD ratio at baseline (p=0.02) and 24h (p=0.003) were significantly associated with favorable outcome. These results suggested that FD ratio showed a trend of decline after stroke onset. Presence of FD within 7days was associated with favorable functional outcome in acute MCA/ICA occlusive stroke patients.

Fluid-attenuated inversion recovery vascular hyperintensities in predicting cerebral hyperperfusion after intracranial arterial stenting.

No reliable imaging sign predicting cerebral hyperperfusion after intracranial arterial stenting (IAS) had been described in the literature. This study evaluated the effect of fluid-attenuated inversion recovery vascular hyperintensities (FVHs), also called hyperintense vessel sign on T2-weighted fluid-attenuated inversion recovery (T2-FLAIR) MR images, in predicting significant increase in cerebral blood flow (CBF) defined by arterial spin labeling (ASL) after IAS. We reviewed ASL CBF images and T2-FLAIR MR images before (D0), 1day after (D1), and 3days after (D3) IAS of 16 patients. T1-weighted MR images were used as cerebral maps for calculating CBF. The changes in CBF values after IAS were calculated in and compared among stenting and nonstenting vascular territories. An increase more than 50% of CBF was considered as hyperperfusion. The effect of FVHs in predicting hyperperfusion was calculated. The D1 CBF value was significantly higher than the D0 CBF value in stenting vascular, contralateral anterior cerebral artery, contralateral middle cerebral artery, and contralateral posterior cerebral artery (PCA) territories (all P<.05). The D1 and D3 CBF values were significantly higher than the D0 CBF value in overall vascular (P<.001), overall nonstenting vascular (P<.001), and ipsilateral PCA (P<.05) territories. The rate of more than 50% increases in CBF was significantly higher in patients who exhibited asymmetric FVHs than in those who did not exhibit these findings. FVHs could be a critical predictor of a significant increase in CBF after IAS.

Two-Stage Cerebral Hemodynamic Changes in Staged Carotid Angioplasty and Stenting

We sought to assess the different patterns of cerebral hemodynamic changes in staged carotid angioplasty and stenting (CAS). We prospectively recruited a cohort of patients with regular angioplasty or staged angioplasty from October 2013 to August 2015. The hemodynamic changes, including peak systolic, end-diastolic, and mean flow velocities in the ipsilateral middle cerebral artery (MCA) and the contralateral anterior cerebral artery (ACA), were recorded by transcranial Doppler ultrasound. Between October 2013 to August 2015, 25 patients (age range from 48 to 78 years, 96% male) with CAS were recruited, of whom 13 patients received staged angioplasty and 12 patients received regular angioplasty. Patients in the staged angioplasty group showed a higher degree of stenosis in the internal carotid artery. After the procedure, the peak systolic, diastolic, and mean flow velocities in the ipsilateral MCA in the staged angioplasty group were significantly higher than those in the regular angioplasty group (P = .028, .036, and .027, respectively). In the staged angioplasty group, first, the peak systolic, end-diastolic, and mean flow velocities in the contralateral ACA decreased significantly soon after balloon dilation in stage I (P = .042, .033, and .034, respectively). Second, the peak systolic, diastolic, and mean flow velocities in the ipsilateral MCA increased after stent placement in stage II (P = .006, .042, and .003, respectively). Two-stage hemodynamic changes were observed in staged angioplasty. The velocities in the ipsilateral MCA started to increase significantly after the collateral flow diminished.

Circle of Willis Collateral During Temporary Internal Carotid Artery Occlusion II: Observations From Computed Tomography Angiography.

The Circle of Willis (CoW) is the most effective collateral circulation to the brain during internal carotid artery (ICA) occlusion. Carotid stump pressure (CSP) is an established surrogate measure of the cerebral collateral circulation. This study aims to use hemodynamic and computed tomography angiography measurements to determine the strongest influences upon the dependent variable, CSP. These findings could help clinicians noninvasively assess the adequacy of the collateral circulation and facilitate surgical risk assessment in an outpatient setting. CSP and mean arterial pressure were measured during carotid endarterectomy or during carotid balloon test occlusion in 92 patients. Intracranial arterial diameters were measured on computed tomography angiography at 16 different locations. Univariate and multivariate analyses were used to determine the key factors associated with CSP. In a subgroup of individuals (n=27) with severe (>70% North American Symptomatic Carotid Endarterectomy Trial) contralateral stenosis or occlusion, the same analysis was performed. The contralateral anterior cerebral artery proximal to anterior communicating artery (A1) of the CoW had the strongest influence upon CSP, followed by the mean arterial pressure, the contralateral ICA diameter, and the anterior communicating artery diameter (R 2=0.364). In the subgroup with high-grade contralateral ICA stenosis, the ipsilateral posterior communicating artery exerted the strongest influence (R 2=0.620). During ICA occlusion, the anterior CoW dominates in preserving collateral flow, especially the contralateral A1 segment. In individuals with high-grade contralateral carotid stenosis, the posterior communicating artery calibre becomes a dominant influence. The most favourable anatomy consists of large contralateral A1 and anterior communicating arteries, and no contralateral carotid stenosis.

The role of the circle of Willis in internal carotid artery stenosis and anatomical variations: a computational study based on a patient-specific three-dimensional model.

BackgroundThe aim of this study is to provide better insights into the cerebral perfusion patterns and collateral mechanism of the circle of Willis (CoW) under anatomical and pathological variations.MethodsIn the current study, a patient-specific three-dimensional computational model of the CoW was reconstructed based on the computed tomography (CT) images. The Carreau model was applied to simulate the non-Newtonian property of blood. Flow distributions in five common anatomical variations coexisting with different degrees of stenosis in the right internal carotid artery (RICA) were investigated to obtain detailed flow information.ResultsWith the development of stenosis in unilateral internal carotid artery (ICA), the cerebral blood supply decreased when the degree of stenosis increased. The blood supply of the ipsilateral middle cerebral artery (MCA) was most affected by the stenosis of ICA. The anterior communicating artery (ACoA) and ipsilateral posterior communicating artery (PCoA) functioned as the important collateral circulation channels when unilateral stenosis occurred. The blood flow of the anterior circulation and the total cerebral blood flow (CBF) reached to the minimum in the configuration of the contralateral proximal anterior cerebral artery (A1) absence coexisting with unilateral ICA stenosis.ConclusionsCommunicating arteries provided important collateral channels in the complete CoW when stenosis in unilateral ICA occurred. The cross-flow in the ACoA is a sensitive indicator of the morphological change of the ICA. The collateral function of the PCoA on the affected side will not be fully activated until a severe stenosis occurred in unilateral ICA. The absence of unilateral A1 coexisting with the stenosis in the contralateral ICA could be the most dangerous configuration in terms of the total cerebral blood supply. The findings of this study would enhance the understanding of the collateral mechanism of the CoW under different anatomical variations.

Rare complication characterized by late-onset transient neurological symptoms without hyperperfusion after carotid artery stenting: A report of three cases

We experienced a rare complication after carotid artery stenting (CAS) characterized by transient neurological symptoms with no evidence of distal emboli or hyperperfusion. Using neuroimaging, we investigated the pathogenesis of the complication that occurred after CAS in three patients who developed neurological symptoms over a period of ten hours after CAS and improved within two days. None of the three patients showed signs of fresh infarctions on diffusion-weighted imaging or hyperperfusion on single-photon emission computed tomography. However, high signal intensity was observed in the leptomeningeal zone of the cerebral hemisphere on the stent side in all three patients and in the leptomeningeal zone of the contralateral anterior cerebral artery territory in one patient. These areas were assessed using fluid-attenuated inversion recovery (FLAIR) magnetic resonance imaging without gadolinium administration. The high signal intensity in the leptomeningeal zone disappeared as the symptoms improved. Based on the transient nature of the neurological disorders and the normalization of FLAIR imaging findings in these patients, the pathogenesis of this complication might have been vasogenic edema due to vasoparalysis of the local vessels caused by the hemodynamic changes occurring after CAS.