Cerebral hyperperfusion after carotid endarterectomy is associated with preoperative hemodynamic impairment and intraoperative cerebral ischemia

A case of intracerebral hemorrhage due to cerebral hyperperfusion after stenting for acute cervical carotid artery dissection

Urgent carotid artery stenting (CAS) is effective for treatment-resistant cervical internal carotid artery dissection (CICAD). We experienced a 37-year-old woman who presented with sudden onset of cervical pain, blurred vision in the right eye, and numbness in the left upper and lower extremities. Due to neurological deterioration resulting from hemodynamic impairment, urgent CAS was performed under general anesthesia. Brain perfusion single-photon emission computed tomography performed immediately after CAS showed increased blood flow in the right hemisphere despite no evidence of hemorrhage or ischemic lesion on brain computed tomography (CT). Systolic blood pressure was therefore strictly controlled below 110 mm Hg perioperatively. However, the day after CAS, a follow-up CT showed intracerebral hemorrhage in the right temporal lobe. Urgent CAS in patients with progressive deterioration of hemodynamic impairment caused by CICAD may induce intracerebral hemorrhage due to cerebral hyperperfusion. Care should be taken to recognize and manage this phenomenon during the perioperative period.

Multidelay MR Arterial Spin Labeling Perfusion Map for the Prediction of Cerebral Hyperperfusion After Carotid Endarterectomy

BACKGROUND

Multidelay arterial spin labeling (ASL) generates time-resolved perfusion maps, which may provide sufficient and accurate hemodynamic information in carotid stenosis.

PURPOSE

To use imaging markers derived from multidelay ASL magnetic resonance imaging (MRI) and to determine the optimal strategy for predicting cerebral hyperperfusion after carotid endarterectomy (CEA).

STUDY TYPE

Prospective observational cohort.

SUBJECTS

A total of 79 patients who underwent CEA for carotid stenosis.

FIELD STRENGTH/SEQUENCE

A 3.0 T/pseudo-continuous ASL with three postlabeling delays of 1.0, 1.57, and 2.46 seconds using fast-spin echo readout.

ASSESSMENT

Cerebral perfusion pressure, antegrade, and collateral flow were scored on a four-grade ordinal scale based on preoperative multidelay ASL perfusion maps. Simultaneously, quantitative hemodynamic parameters including cerebral blood flow (CBF), arterial transit time (ATT), relative CBF (rCBF) and relative ATT (rATT; ipsilateral/contralateral values) were calculated. On the CBF ratio map obtained through dividing postoperative by preoperative CBF map, regions of interest were placed covering ipsilateral middle cerebral artery territory. Three neuroradiologists conducted this procedure. Cerebral hyperperfusion was defined as a CBF ratio >2.

STATISTICAL TESTS

Weighted κ values, independent sample t test, chi-square test, Mann-Whitney U-test, multivariable logistic regression analysis, receiver-operating characteristic curve analysis, and Delong test. Significance level was P < 0.05.

RESULTS

Cerebral hyperperfusion was observed in 15 (19%) patients. Higher blood pressure (odd ratio [OR] = 1.08) and carotid near-occlusion (NO; OR = 7.31) were clinical risk factors for postoperative hyperperfusion. Poor ASL perfusion score (OR = 37.33), decreased CBF (OR = 0.74), prolonged ATT (OR = 1.02), lower rCBF (OR = 0.91), and higher rATT (OR = 1.12) were independent imaging predictors of hyperperfusion. ASL perfusion score exhibited the highest specificity (95.3%), while CBF exhibited the highest sensitivity (93.3%) for the prediction of hyperperfusion. When combined with ASL perfusion score, CBF and ATT, the predictive ability was significantly higher than using blood pressure and NO alone (AUC: 0.98 vs. 0.78).

DATA CONCLUSIONS

Multidelay ASL can accurately predict cerebral hyperperfusion after CEA with high sensitivity and specificity.

EVIDENCE LEVEL

2 TECHNICAL EFFICACY: Stage 5.

Prediction of cerebral hyperperfusion following carotid endarterectomy using intravoxel incoherent motion magnetic resonance imaging

OBJECTIVES

One of the risk factors for cerebral hyperperfusion following carotid endarterectomy (CEA) is a chronic reduction in cerebral perfusion pressure due to internal carotid artery (ICA) stenosis, which is clinically detected as increased cerebral blood volume (CBV). The perfusion fraction (f) is one of the intra-voxel incoherent motion (IVIM) parameters obtained using magnetic resonance (MR) imaging that theoretically reflects CBV. The present study aimed to determine whether preoperative IVIM-f on MR imaging predicts development of cerebral hyperperfusion following CEA.

MATERIALS AND METHODS

Sixty-eight patients with unilateral ICA stenosis (≥ 70%) underwent preoperative diffusion-weighted 3-T MR imaging, and IVIM-f maps were generated from these data. Quantitative brain perfusion single-photon emission computed tomography (SPECT) was performed before and immediately after CEA. Regions-of-interest (ROIs) were automatically placed in the bilateral middle cerebral artery territories in all images using a three-dimensional stereotactic ROI template, and affected-to-contralateral ratios in the ROIs were calculated on IVIM-f maps.

RESULTS

Nine patients (13%) exhibited postoperative hyperperfusion (cerebral blood flow increases of ≥ 100% compared with preoperative values in the ROIs on brain perfusion SPECT). Only high IVIM-f ratios were significantly associated with the occurrence of postoperative hyperperfusion (95% confidence interval, 253.8-6774.2; p = 0.0031) on logistic regression analysis. The sensitivity, specificity, and positive and negative predictive values of the IVIM-f ratio to predict the occurrence of postoperative hyperperfusion were 100%, 81%, 45%, and 100%, respectively.

CONCLUSIONS

Preoperative IVIM-f on MR imaging can predict development of cerebral hyperperfusion following CEA.

Intraoperative Transcranial Doppler Monitoring Predicts the Risk of Cerebral Hyperperfusion Syndrome After Carotid Endarterectomy

OBJECTIVE

Cerebral hyperperfusion syndrome (CHS) is a rare but serious complication following carotid endarterectomy (CEA). The aim of this study was to identify intraoperative transcranial Doppler (TCD) hemodynamic predictors of CHS after CEA.

METHODS

Between January 2013 and December 2018, intraoperative TCD monitoring was performed for 969 patients who underwent CEA. The percentage increase in the mean velocity of the middle cerebral artery (MCAV%) at 3 postdeclamping time points (immediately after declamping, 5 minutes after declamping, and after suturing the skin) over baseline was compared between CHS and non-CHS patients.

RESULTS

CHS was diagnosed in 31 patients (3.2%), including 11 with intracranial hemorrhage. The MCAV% values at the 3 postdeclamping time points over baseline were 177% (81%-275%), 90% (41%-175%), and 107% (55%-191%) in the CHS group, significantly higher than those in the non-CHS group (40% [14%-75%], 15% [1%-36%], and 18% [3%-41%], respectively, all P < 0.001). Receiver operating characteristic curve analysis showed that the 3 intraoperative MCAV% parameters all had excellent accuracy in identifying CHS (areas under the curve: 0.854, 0.839, and 0.858, respectively, all P < 0.001). The predictive value of the model consisting only of preoperative parameters was significantly increased by adding the intraoperative TCD hemodynamic parameters (area under the curve: 0.747 vs. 0.858, P = 0.006). Multivariate analyses identified the intraoperative MCAV% immediately after declamping (odds ratio: 9.840, 95% confidence interval: 2.638-36.696, P < 0.001) as an independent predictor of CHS.

CONCLUSIONS

Our results indicate that intraoperative TCD monitoring helps predict CHS after CEA at an early stage.

Relationship between cerebral hyperperfusion syndrome and the immediate change of cerebral blood flow after carotid artery stenting evaluated by single-photon emission computed tomography

PURPOSE

Cerebral hyperperfusion syndrome (CHS) is a critical complication after carotid artery stenting (CAS). However, few CAS studies have evaluated immediate and temporary changes in ipsilateral cerebral blood flow (CBF) quantitatively. The study was performed to evaluate immediate changes in CBF after CAS and subsequent CBF changes in patients with cerebral hyperperfusion (HP) using ¹²³I-IMP SPECT.

METHODS

The subjects were 223 patients with chronic extracranial carotid artery stenosis who underwent CAS in our department between March 2010 and March 2020. Quantitative CBF and cerebrovascular reactivity to acetazolamide in the middle cerebral artery were assessed before CAS by ¹²³I-IMP SPECT. CBF was also measured immediately after CAS by ¹²³I-IMP SPECT. When HP was detected, CBF was measured again 3 and 7 days after CAS.

RESULTS

The median (interquartile range) ipsilateral quantitative CBF change after CAS was - 0.1% (- 9.5-8.2%), and the upper value of the 95% CI of the quantitative CBF change was 48.2%. Thus, we defined HP after CAS as an increase in quantitative CBF of > 48.2% compared with the preoperative value. Of 223 patients, 5 (2.2%) had HP, and 4 of these patients (80%) developed CHS. In the CHS patients, HP was maintained for about 3 days and improved after about 7 days.

CONCLUSION

An immediate CBF increase of > 48.2% after CAS may lead to development of CHS. In CHS after CAS, HP persisted for about 1 week and postoperative management may be required for at least 1 week.

Arterial transit artifacts on arterial spin labeling MRI can predict cerebral hyperperfusion after carotid endarterectomy: an initial study

OBJECTIVES

To investigate whether preoperative arterial spin labeling (ASL) MRI can predict cerebral hyperperfusion after carotid endarterectomy (CEA) in patients with carotid stenosis.

METHODS

Consecutive patients with carotid stenosis who underwent CEA between May 2015 and July 2021 were included. For each patient, a cerebral blood flow ratio (rCBF) map was obtained by dividing postoperative CBF with preoperative CBF images from two pseudo-continuous ASL scans. Hyperperfusion regions with rCBF > 2 were extracted and weighted with rCBF to calculate the hyperperfusion index. According to the distribution of the hyperperfusion index, patients were divided into hyperperfusion and non-hyperperfusion groups. Preoperative ASL images were scored based on the presence of arterial transit artifacts (ATAs) in 10 regions of interest corresponding to the Alberta Stroke Programme Early Computed Tomography Score methodology. The degree of stenosis and primary and secondary collaterals were evaluated to correlate with the ASL score. Logistic regression and receiver operating characteristic curve analyses were performed to assess the predictive ability of the ASL score for cerebral hyperperfusion.

RESULTS

Of 86 patients included, cerebral hyperperfusion was present in 17 (19.8%) patients. Carotid near occlusion, opening of posterior communicating arteries with incomplete anterior semicircle, and leptomeningeal collaterals were associated with lower ASL scores (p < 0.05). The preoperative ASL score was an independent predictor of cerebral hyperperfusion (OR = 0.48 [95% CI [0.33-0.71]], p < 0.001) with the optimal cutoff value of 25 points (AUC = 0.98, 94.1% sensitivity, 88.4% specificity).

CONCLUSIONS

Based on the presence of ATAs, ASL can non-invasively predict cerebral hyperperfusion after CEA in patients with carotid stenosis.

KEY POINTS

• Carotid near occlusion, opening of posterior communicating arteries with incomplete anterior semicircle, and leptomeningeal collaterals were associated with lower ASL scores. • The ASL score performed better than the degree of stenosis, type of CoW, and leptomeningeal collaterals, as well as the combination of the three factors for the prediction of cerebral hyperperfusion. • For patients with carotid stenosis, preoperative ASL can non-invasively identify patients at high risk of cerebral hyperperfusion after carotid endarterectomy without complex post-processing steps.

Peri-Procedural Management of Hemodynamic Instability in Patients Undergoing Carotid Revascularization

Acute perioperative changes in arterial pressure occur frequently, particularly in patients with cardiovascular disease or those receiving vasoactive medications, or in relation to certain cardiovascular surgical procedures. Hemodynamic Instability (HI) are common in patients undergoing carotid revascularization because of unique patho-physiological and surgical factors. The operation, by necessity, disrupts the afferent pathway of the baroreflex, which can lead to postendarterectomy HI. Poor arterial pressure control is associated with increased morbidity and mortality after carotid revascularization, but good control of arterial pressure is often difficult to achieve in practice. The incidence, implications, and etiology of HI associated with carotid surgery are reviewed, and some recommendations made for its management. Close monitoring and titration of therapy are probably the most important considerations rather than specific choice of agents.

Direct Ischemic Postconditioning After Carotid Endarterectomy in the Prevention of Postoperative Cerebral Ischemic Complications—Observational Case–Control Study

Introduction:

Ischemic postconditioning (IPCT) represents one of the several therapeutic strategies to attenuate ischemic reperfusion injury (IR) after carotid endarterectomy (CEA). We here present the first in-human study of IPCT in carotid surgery.

Methods:

The study represents an observational case-control study, with the data collected in our Institution carotid database. From December 2015 to December 2020, a total of 300 patients were included in our study; IPCT group consisted of 148 patients in whom ischemic postconditioning was performed while control group consisted of 152 patients in whom IPCT was not performed. Indications for IPCT technique were: severe unilateral internal carotid artery (ICA) stenosis (>90%), severe bilateral ICA stenosis (>80%), severe ICA stenosis (>80%) with contralateral ICA occlusion and ICA subocclusion. IPCT was performed by applying 6 cycles of 30 sec reperfusion (declamping of ICA)/30 sec ischemia (clamping of ICA) after finishing the procedure and initial declamping. Two groups of patients were compared in terms of occurrence of intrahospital and early postoperative stroke, TIA (transient ischemic attack) and neurologic morbidity.

Results:

Cumulative incidence of intrahospital postoperative stroke or TIA was significantly higher in the control group (5.3% vs 0.7%, P = .036). According to carotid plaque characteristics, patients in the IPCT group had significantly more frequent presence of heterogenous plaque, as well as ulcerated plaque, which was associated with the absence of postoperative stroke and significantly lower cumulative rate of TIA/stroke when compared to the control group (43.9% vs 8% and 47.3% vs 1.5%). During the follow-up period of 1 month after the surgery, there were no cases of stroke, TIA and deaths due to neurological causes in both groups of patients.

Conclusion:

Our results showed that IPCT significantly reduced the incidence of postoperative cerebral ischemic complications after CEA in high-risk patients for IR injury when compared to the control group.

Modifications in Near Infrared Spectroscopy for Cerebral Monitoring During Carotid Endarterectomy in Asymptomatic and Symptomatic Patients

BACKGROUND

To evaluate trends and differences in Near Infrared Spectroscopy (NIRS) monitoring during carotid endarterectomy (CEA) in patients affected by asymptomatic and symptomatic carotid artery stenosis, to predict postoperative neurological complications (PNCs).

METHODS

NIRS data of CEAs performed in a University Hospital were retrospectively reviewed. All the interventions were performed under general anesthesia and patients with intraoperative complications were excluded. Mean regional Oxygen Saturation Index (rSO₂), pre-clamp values (mean baseline value, MBv and Single Mark Baseline value, SMBv) were collected and compared to the lowest rSO₂ values during carotid cross-clamp (LSO₂v) calculated within 3 min (percentage drop, PD). ROC curve analysis with Youden's Test was performed to determine the best threshold value of PD, in order to identify PNCs in both asymptomatic and symptomatic groups.

RESULTS

Between 2007 and 2015, a total of 399 CEAs were consecutively performed with NIRS monitoring. Three-hundred-seventy-two CEAs in 355 patients were reviewed. Asymptomatic stenoses were 291 (81.9%), eleven (2.9%) PNC were registered (5 in asymptomatic and 6 in symptomatic group). Asymptomatic and symptomatic diseases had different MBv (69.5 ± 7.5 vs. 71.8 ± 6.9, respectively; P = 0.011) and similar rSO₂ value during carotid clamping (63.7 ± 8.0 vs. 63.7 ± 6.7, respectively: P = 0.958). Asymptomatic patients experiencing PNCs had a greater PD than non-PNCs group (20.5 ± 10.2% vs. 12.5 ± 7.6%, respectively using MBv as baseline value; P = 0.002), in contrast, in symptomatic patients, in which a low PD was associated with PNCs, it does not reach statistical significance (using MBv, 12.6 ± 5.4% vs. 14.8 ± 6.7%, respectively; P= 0.476). In order to detect PNCs, ROC analysis revealed an optimal PD cut-off value of -17% in asymptomatic CEAs. (Sensibility (Se) 0.80, Specificity (Sp) 0.76, PPV 0.05, NPV 0.99, Youden's index 0.56; P = 0.020) In symptomatic a threshold value of -9% was found, without reaching statistical significance.

CONCLUSIONS

NIRS as cerebral monitoring during CEA can predict PNCs in asymptomatic stenosis. Asymptomatic and symptomatic groups differ in baseline and intraprocedural cut-off values to detect an augmented PNCs risk.

Hypocapnia Induced by Hyperventilation with Indocyanine Green Kinetics Detects the Effect of Staged Carotid Angioplasty to Avoid Hyperperfusion in Patients with Impaired Cerebral Hemodynamic Reserve

Cerebral hyperperfusion syndrome (CHS) is a serious complication following carotid artery stenting (CAS). Staged angioplasty (AP) could potentially prevent CHS and hyperperfusion phenomenon (HPP) after revascularization. However, methods for measuring the effects of staged AP on cerebral hemodynamic reserve have not been established. Here, we evaluated whether indocyanine green kinetics and near-infrared spectroscopy (ICG-NIRS) with hypocapnia induced by hyperventilation can detect the effects of staged AP on hemodynamic reserve to prevent CHS after CAS. Participants comprised 44 patients at high risk of CHS, whose ipsilateral cerebrovascular reactivity (CVR) was impaired on preoperative single photon emission computed tomography (SPECT). Patients were divided into a staged AP group (n=13) and a regular CAS group (n=31). In the staged AP group, stenting was performed 3 weeks after staged AP. In the regular CAS group, 16 cases (52%) showed HPP, and five (16%) presented with CHS after CAS, while no HPP or CHS occurred in the staged AP group (p=0.001). Changes in blood flow index (BFI) and time to peak (TTP) ratio during hypocapnia calculated from ICG-NIRS indicated a significant linear relationship with preprocedural CVR on SPECT (r=-0.710, 0.632, respectively; p<0.0001 each). BFI and TTP ratios during hypocapnia were significantly improved after staged AP (p<0.001 each). Furthermore, significant linear correlations were observed between BFI and TTP ratio during hypocapnia and postoperative asymmetry index AI (r=0.405, -0.475, respectively; p<0.01 each). Hypocapnia induced by hyperventilation under ICG-NIRS appears useful for detecting the effects of staged AP on hemodynamic reserve in patients at high risk of CHS.

Age corrected changes in intracranial hemodynamics after carotid endarterectomy

BACKGROUND

Transcranial Doppler ultrasound (TCD) is a frequently used method to monitor brain perfusion during and following carotid endarterectomy (CEA). Our aim was to define the normally occurring changes of intracranial hemodynamics in patients undergoing CEA measuring recently developed TCD parameters.

METHODS

A retrospective, single-center cohort study was performed. Patients undergoing CEA were evaluated pre- and postoperatively from day 0 to day 3 measuring middle cerebral artery flow velocity (MCAFV). The following parameters were analyzed: the first systolic peak (Sys1), the second systolic peak (Sys2) and diastolic flow velocity at a fixed time after heartbeat onset (Dias@560). These parameters linearly decrease with age and were, therefore, transformed to Z-scores.

RESULTS

Three hundred eighteen patients were included with a mean age of 70.8 years. Most patients were male (71%). Compared to preoperatively, the Z-scores of Sys1 and Sys2 were larger on postoperative day 3: +1.12 standard deviation (SD) or 16.0 cm/s (CI: 0.93 to 1.32; P<0.001) and +0.55 SD or 7.8 cm/s (CI: 0.35 to 0.74; P<0.001), respectively. The Z-score for Dias@560 was smaller than preoperatively: -0.23 SD or -1.9 cm/s (CI: -0.41 to -0.05, P=0.015).

CONCLUSIONS

Under normal circumstances Sys1 profits more from CEA than Sys2, whilst diastolic flow velocity decreases. This indicates a return to normal arteriolar vascular resistance. Carefully describing normal changes in MCAFV, may in future enable discrimination of abnormalities, such as hyperperfusion syndrome.

Usefulness of 2D-Perfusion Analysis for the Assessment of Unilateral Cervical Internal Carotid Artery Stenosis

Objective

We investigated the usefulness of 2D-perfusion analysis for the evaluation of cerebral blood flow in unilateral cervical internal carotid artery stenosis.

Methods

We conducted a 2D-perfusion analysis during cerebral angiography and ¹²³I-iodoamphetamine (IMP) single photon emission computed tomography (SPECT) for unilateral cervical internal carotid artery stenosis without contralateral stenosis. The relationship between the ratio of the lesion side to the normal side in the parameters obtained by 2D-perfusion and the value calculated by stereotactic extraction estimation (SEE) analysis of SPECT was statistically examined.

Results

The ratios of the lesion side to the normal side regarding the peak arrival time (AT; time to peak [TTP]) of the contrast agent and the mean filling time (mean transit time [MTT]) of the contrast agent in 2D-perfusion significantly correlated with the area of Stage II and increase ratio (I.R) ≤30% in the SEE analysis (p = 0.002, 0.003).

Conclusion

2D-perfusion analysis can be used to estimate the extent of impaired cerebrovascular reserve (CVR) area in unilateral internal carotid artery stenosis.

Basal and Acetazolamide Brain Perfusion SPECT in Internal Carotid Artery Stenosis

Internal carotid artery (ICA) stenosis including Moyamoya disease needs revascularization when hemodynamic insufficiency is validated. Vascular reserve impairment was the key to find the indication for endarterectomy/bypass surgery in the atherosclerotic ICA stenosis and to determine the indication, treatment effect, and prognosis in Moyamoya diseases. Vascular reserve was quantitatively assessed by 1-day split-dose I-123 IMP basal/acetazolamide SPECT in Japan or by Tc-99m HMPAO SPECT in other countries using qualitative or semi-quantitative method. We summarized the development of 1-day basal/ acetazolamide brain perfusion SPECT for ICA stenosis, both quantitative and qualitative methods, and their methodological issues regarding (1) acquisition protocol; (2) qualitative assessment, either visual or deep learning-based; (3) clinical use for atherosclerotic ICA steno-occlusive diseases and mostly Moyamoya diseases; and (4) their impact on the choice of treatment options. Trials to use CT perfusion or perfusion MRI using contrast materials or arterial spin labeling were briefly discussed in their endeavor to use basal studies alone to replace acetazolamide-challenge SPECT. Theoretical and practical issues imply that basal perfusion evaluation, no matter how much sophisticated, will not disclose vascular reserve. Acetazolamide rarely causes serious adverse reactions but included fatality, and now, we need to monitor patients closely in acetazolamide-challenge studies.

Hyperventilation and breath-holding test with indocyanine green kinetics predicts cerebral hyperperfusion after carotid artery stenting

Cerebral hyperperfusion syndrome (CHS) is a serious complication following carotid artery stenting (CAS), but definitive early prediction of CHS has not been established. Here, we evaluated whether indocyanine green kinetics and near-infrared spectroscopy (ICG-NIRS) with hyperventilation (HV) and the breath-holding (BH) test can predict hyperperfusion phenomenon after CAS. The blood flow index (BFI) ratio during HV and BH was prospectively monitored using ICG-NIRS in 66 patients scheduled to undergo CAS. Preoperative cerebrovascular reactivity (CVR) and the postoperative asymmetry index (AI) were also assessed with single-photon emission computed tomography before and after CAS and the correlation with the BFI HV/rest ratio, BFI BH/rest ratio was evaluated. Twelve cases (18%) showed hyperperfusion phenomenon, and one (1.5%) showed CHS after CAS. A significant linear correlation was observed between the BFI HV/rest ratio, BFI BH/rest ratio, and preoperative CVR. A significant linear correlation was observed between the BFI HV/rest ratio and postoperative AI (r = 0.674, P < 0.0001). A BFI HV/rest ratio of 0.88 or more was the optimal cut-off point to predict hyperperfusion phenomenon according to receiver operating characteristic curve analyses. HV and BH test under ICG-NIRS is a useful tool for detection of hyperperfusion phenomenon in patients who underwent CAS.

ASL perfusion features and type of circle of Willis as imaging markers for cerebral hyperperfusion after carotid revascularization: a preliminary study

OBJECTIVES

Cerebral hyperperfusion (CH) could be a disastrous outcome causing complication after carotid revascularization if not managed properly and timely. The aim of this study was to investigate the association between preoperative arterial spin labelling (ASL) perfusion features and circle of Willis (CoW) pattern with CH.

METHODS

Forty-eight consecutive carotid stenosis patients who underwent carotid endarterectomy (CEA) or carotid artery stenting (CAS) were enrolled. All patients had single post-labelling delay (PLD) ASL, territory-ASL, and 3-dimensional time-of-flight MR angiography (3D TOF MRA) within 2 weeks before surgery and within 3 days after surgery. Spatial coefficient of variation (CoV) of cerebral blood flow (CBF), whole brain, and territory perfusion volume ratio were calculated from ASL and territory-ASL. Postoperative CoW was classified into two groups based on patency of the first segment of the anterior cerebral arteries (A1) and anterior communicating artery (AcomA). ASL perfusion features, type of CoW, and clinical characteristics were analyzed between CH group and non-CH group to identify CH risk factors.

RESULTS

Higher CoV (p = 0.005) of CBF, lower whole brain perfusion volume ratio (p = 0.012), missing any of A1 or AcomA in CoW (p = 0.002 for postoperative MRA and p = 0.004 for preoperative MRA), and large artery stroke history (p = 0.028) were significantly associated with higher risk of CH. Two cases with cerebral hyperperfusion syndrome (CHS) were also discussed, and their perfusion and angiographic features were shown.

CONCLUSIONS

Single-PLD ASL and MRA might be useful and non-invasive imaging tools to identify patients with higher risk of CH after carotid revascularization.

KEY POINTS

• Cerebral hyperperfusion is a critical complication after carotid endarterectomy or carotid artery stenting. • ASL and MRA can be used to identify patients at higher risk of cerebral hyperperfusion • Pattern of circle of Willis, ASL perfusion features, and whole brain perfusion volume ratio are potential predicting markers for hyperperfusion after carotid revascularization.

Comparison of Monitoring of Cerebral Blood Flow by c-FLOW and Transcranial Doppler in Carotid Endarterectomy

OBJECTIVE

To prospectively compare the use of the cerebral blood flow monitor (c-FLOW) and transcranial Doppler (TCD) as 2 techniques for assessing brain perfusion during carotid endarterectomy.

METHODS

This was a prospective, single-center, observational study. All patients were monitored using c-FLOW and TCD during the operation. Changes from baseline values of cerebral blood flow index and blood flow velocity of middle cerebral artery (V-MCA) were recorded following carotid artery clamping and unclamping. The correlation analysis was conducted for c-FLOW and TCD monitoring values.

RESULTS

Seventy-three consecutive patients were enrolled from August 2015 to March 2016. No death or stroke occurred during the postoperative hospitalization. Fresh infarction was identified on magnetic resonance imaging in 17 patients. Ten patients showed a significant decrease of V-MCA following carotid clamping. A shunt was placed for only 4. The Pearson correlation index between CFI and V-MCA was 0.647 (P < 0.001). A cut-off of 21% decrease of CFI was proposed as optimal to detect intraoperative hypoperfusion. Seven patients were diagnosed as having hyperperfusion by TCD monitoring. The Pearson correlation index between CFI and V-MCA was 0.286 (P = 0.014). A cut-off of 15% increase of CFI following carotid unclamping was suggested as optimal to detect the postoperative hyperperfusion.

CONCLUSIONS

c-FLOW could continuously and noninvasively monitor the cerebral blood flow in real-time during carotid endarterectomy and effectively detect the intraoperative hypoperfusion and postoperative hyperperfusion as defined by TCD so that it may serve as a favorable modality in future intraoperative monitoring.

Near-Infrared Spectroscopy versus Transcranial Doppler-Based Monitoring in Carotid Endarterectomy

Background

Proper monitoring of cerebral perfusion during carotid artery surgery is crucial for determining if a shunt is needed. We compared the safety and reliability of near-infrared spectroscopy (NIRS) with transcranial Doppler (TCD) for cerebral monitoring.

Methods

This single-center, retrospective review was conducted on patients who underwent carotid endarterectomy (CEA) using selective shunt-based TCD or NIRS at Daegu Catholic University Medical Center from November 2009 to June 2016. Postoperative complications were the primary outcome, and the distribution of risk factors between the 2 groups was compared.

Results

The medical records of 74 patients (45 TCD, 29 NIRS) were reviewed. The demographic characteristics were similar between the 2 groups. One TCD patient died within the 30-day postoperative period. Postoperative stroke (n=4, p=0.15) and neurologic complications (n=10, p=0.005) were only reported in the TCD group. Shunt usage was 44.4% and 10.3% in the TCD and NIRS groups, respectively (p=0.002).

Conclusion

NIRS-based selective shunting during CEA seems to be safe and reliable for monitoring cerebral perfusion in terms of postoperative stroke and neurologic symptoms. It also reduces unnecessary shunt usage.

Indocyanine green kinetics with near-infrared spectroscopy predicts cerebral hyperperfusion syndrome after carotid artery stenting

Background

Cerebral hyperperfusion syndrome (HPS) is a potentially life-threatening complication following carotid artery stenting (CAS) and carotid endoarterectomy (CEA). Early prediction and treatment of patients at risk for HPS are required in patients undergoing CAS because HPS occurs significantly earlier after CAS than CEA. Near-infrared spectroscopy (NIRS) is often used for monitoring, and indocyanine green (ICG) kinetics by NIRS (ICG-NIRS) can detect reductions in cerebral perfusion in patients with acute stroke. However, whether ICG-NIRS can predict postoperative hyperperfusion phenomenon (HP) after carotid revascularization is unclear.

Objective

Here, we evaluated whether the blood flow index (BFI) ratio calculated from a time-intensity curve from ICG-NIRS monitoring can predict HPS after CAS.

Methods

The BFI ratio was prospectively monitored using ICG-NIRS in 135 patients undergoing CAS. Preoperative cerebrovascular reactivity (CVR) and the postoperative asymmetry index (AI) were also assessed with single-photon emission computed tomography before and after CAS, and the correlation was evaluated. In addition, patients were divided into two groups, a non-HP group (n = 113) and an HP group (n = 22), and we evaluated the correlation with hemodynamic impairment in the ipsilateral hemisphere and clinical results.

Results

Twenty-two cases (16%) showed HP, and four (3%) showed HPS after CAS. The BFI ratio calculated from ICG-NIRS showed a significant linear correlation with preoperative CVR and postoperative AI (r = −0.568, 0.538, P < 0.001, <0.001, respectively). The degree of stenosis, the rate of no cross flow, preoperative CVR, and the incidence of HPS were significantly different between the groups.

Conclusions

Measurement of ICG kinetics by NIRS is useful for detection of HPS in patients who underwent CAS.

Effect of carotid endarterectomy on brain damage markers

OBJECTIVES

Carotid endarterectomy (CEA) is a recommended treatment in the prevention of ischemic stroke. However, this procedure may cause neurological complications caused by cerebrovascular damage. While YKL-40 is a proinflammatory protein, neurofilament light polypeptide (NEFL) and brain lipid-binding protein (FABP7) are structural components of the brain. The aim of the study was to investigate YKL-40, NEFL, and FABP7 in the serum of patients undergoing CEA.

MATERIALS AND METHODS

The study included 25 participants who underwent CEA due to internal carotid artery stenosis. Blood samples were taken from each patient at three different intervals: prior to the surgery, 12 h after the surgery, and 48 h after the surgery. Serum levels of these brain damage markers were measured by enzyme-linked immunosorbent assay (ELISA).

RESULTS

The study showed that the serum YKL-40 level was significantly increased 48 h after CEA when compared to the level prior to surgery and also when compared to levels 12 h after surgery. There were no statistically significant differences in serum NEFL and FABP7 levels between all three recorded measurements.

CONCLUSIONS

Data from our study showed that CEA affects serum YKL-40 but not NEFL and FABP7 levels. This implicates that YKL-40 may be a valuable serum marker of brain damage after CEA. However, the observed change in serum YKL-40 level in patients after CEA does not necessarily warrant a change in recommendations concerning the use of this treatment in patients with high-grade internal carotid artery stenosis.

Evaluation of Cerebral Hyperperfusion After Carotid Artery Stenting Using C‑Arm CT Measurements of Cerebral Blood Volume

PURPOSE

Hyperperfusion syndrome (HPS) after carotid artery stenting (CAS) causes serious symptoms; therefore, early evaluation after CAS is considered to be important. Measurement of cerebral blood volume using C‑arm computed tomography (C-arm CBV) has recently become possible. Here, the usefulness of C‑arm CBV for the evaluation of hyperperfusion was investigated.

METHODS

C-arm CBV was measured before and immediately after CAS in 30 patients. The regions of interest (ROI) were set in the bilateral middle cerebral artery perfused regions, and the affected/healthy side ratio of measured C‑arm CBV (CBV ratios) was determined to evaluate cerebral perfusion. For comparing values before and after CAS, the CBV ratio increase rate (postoperative CBV ratios/preoperative CBV ratios) was also determined.

RESULTS

C-arm CBV was successfully measured in 30 patients. Intracerebral hemorrhage (ICH) was detected in 3 patients, and no other patient had hyperperfusion syndrome. In the patients who developed ICH, postoperative C‑arm CBV on the affected side was high, and a marked increase was confirmed in the postoperative CBV ratios. Postoperative CBV ratios were 1.03 ± 0.40 and 1.45 ± 0.68 in the non-ICH and ICH groups, and CBV ratio increase rates were 2.7 ± 24.0% and 28.5 ± 26.7% in the non-ICH and ICH groups, respectively; these differences were statistically significant (P < 0.01).

CONCLUSION

C-arm CT allows CBV measurements immediately after CAS without requiring transport of the patient out of the angiography room, and it may enable the evaluation of hyperperfusion before and after CAS.

Changes in Blood Flow of Anterior and Middle Cerebral Arteries Following Carotid Endarterectomy: A Transcranial Doppler Study

Aim: The aim of the present study was to evaluate the changes in blood flow of anterior and middle cerebral arteries following carotid endarterectomy, using transcranial Doppler (TCD) flow studies.

Patients and methods: This study included 100 patients (72 men, mean age 65 years) who underwent carotid endarterectomy because of high-grade carotid stenosis or symptoms of ischemic stroke. Endarterectomy was performed by a distal shunt between the common carotid and internal carotid arteries. Blood flow in the anterior and middle cerebral arteries was assessed by TCD preoperatively and also in the postoperative period (1st and 4th day; 1st, 6th, and 12th month). Collateral circulation in the Willis circle was evaluated by common carotid compression.

Results: Patients with bilateral carotid stenosis ≥70% exhibited a significantly increased flow velocity in the ipsilateral anterior cerebral artery (ACA), middle cerebral artery (MCA), and in the contralateral ACA. Patients with entirely occluded contralateral internal carotid artery showed the most pronounced changes in cerebral hemodynamics. Blood flow velocities returned to the preoperative values at 1 to 12 months following endarterectomy. Hyperperfusion syndrome was manifested in 14 patients, who exhibited significantly higher flow velocities in the ipsilateral MCA compared with asymptomatic patients.

Conclusions: A transient bilateral increase of blood flow velocity in the anterior part of the Willis circle may often occur in the immediate postoperative period following carotid endarterectomy. Although its clinical significance is not entirely understood, this increase may be associated with cerebral hyperperfusion syndrome.

Cerebral blood flow and autoregulation: current measurement techniques and prospects for noninvasive optical methods

Cerebral blood flow (CBF) and cerebral autoregulation (CA) are critically important to maintain proper brain perfusion and supply the brain with the necessary oxygen and energy substrates. Adequate brain perfusion is required to support normal brain function, to achieve successful aging, and to navigate acute and chronic medical conditions. We review the general principles of CBF measurements and the current techniques to measure CBF based on direct intravascular measurements, nuclear medicine, X-ray imaging, magnetic resonance imaging, ultrasound techniques, thermal diffusion, and optical methods. We also review techniques for arterial blood pressure measurements as well as theoretical and experimental methods for the assessment of CA, including recent approaches based on optical techniques. The assessment of cerebral perfusion in the clinical practice is also presented. The comprehensive description of principles, methods, and clinical requirements of CBF and CA measurements highlights the potentially important role that noninvasive optical methods can play in the assessment of neurovascular health. In fact, optical techniques have the ability to provide a noninvasive, quantitative, and continuous monitor of CBF and autoregulation.

Combining carotid endarterectomy with off-pump coronary artery bypass graft surgery is safe and effective

Background:

We, as neurologists, are frequently consulted to give neurological clearance for surgery in patients who are undergoing coronary artery bypass graft (CABG) surgery and have suffered from stroke or transient ischemic attack (TIA) in past. Similarly clearance is also sought in another group of patients who, though have not suffered from stroke or TIA, but found to have significant carotid stenosis on routine screening prior to surgery. Cardiac surgeons and anesthetists want to know the risk of perioperative stroke in such patients and should carotid endarterectomy (CEA) be done along with CABG. In absence of any clear-cut guideline, neurologists often fail to give any specific recommendation.

Aim:

To find out safety and efficacy of synchronous CEA in patients undergoing CABG.

Design:

Retrospective study.

Materials and Methods:

Out of 3,700 patients who underwent CABG, 150 were found to have severe carotid stenosis of >70%. Out of this, 46 patients with >80% stenosis (three symptomatic and 43 asymptomatic) and one patient with >70% symptomatic carotid stenosis (TIA within last 2 weeks) were taken for simultaneous CEA along with CABG. These three symptomatic carotid patients had suffered from stroke within last 6 months.

Results:

One patient with asymptomatic near total occlusion of carotid artery suffered from hyperperfusion syndrome. None suffered from ischemic stroke, myocardial infarction (MI), or death during perioperative period.

Conclusion:

Combining CEA along with CABG is a safe and effective procedure.

Monitoring of brain and systemic oxygenation in neurocritical care patients

Maintenance of adequate oxygenation is a mainstay of intensive care, however, recommendations on the safety, accuracy, and the potential clinical utility of invasive and non-invasive tools to monitor brain and systemic oxygenation in neurocritical care are lacking. A literature search was conducted for English language articles describing bedside brain and systemic oxygen monitoring in neurocritical care patients from 1980 to August 2013. Imaging techniques e.g., PET are not considered. A total of 281 studies were included, the majority described patients with traumatic brain injury (TBI). All tools for oxygen monitoring are safe. Parenchymal brain oxygen (PbtO2) monitoring is accurate to detect brain hypoxia, and it is recommended to titrate individual targets of cerebral perfusion pressure (CPP), ventilator parameters (PaCO2, PaO2), and transfusion, and to manage intracranial hypertension, in combination with ICP monitoring. SjvO2 is less accurate than PbtO2. Given limited data, NIRS is not recommended at present for adult patients who require neurocritical care. Systemic monitoring of oxygen (PaO2, SaO2, SpO2) and CO2 (PaCO2, end-tidal CO2) is recommended in patients who require neurocritical care.

Pathophysiology of Acute Cerebrovascular Syndrome in Patients With Carotid Artery Stenosis

BACKGROUND:

The mechanisms underlying acute cerebrovascular syndrome in patients with carotid artery stenosis remain unclear.

OBJECTIVE:

To assess the relationships among infarct localization, hemodynamics, and plaque components.

METHODS:

This prospective study included 38 patients with acute cerebrovascular syndrome resulting from ipsilateral carotid artery stenosis. Cerebral infarct localization was categorized into 3 patterns (cortical, border zone, and mixed pattern). Carotid plaque components were evaluated with T1-weighted magnetic resonance imaging and time-of-flight imaging. Cerebral blood flow (CBF) and cerebrovascular reactivity (CVR) were also quantified.

RESULTS:

Infarcts were identified in 38 patients with the use of diffusion-weighted magnetic resonance imaging. On the basis of the assessment of hemodynamics, the cortical pattern was seen in 18 of 21 patients with type 1 ischemia (normal CBF, normal CVR), whereas the mixed pattern was seen in 2 patients with type 2 ischemia (normal CBF, impaired CVR) and 12 of 15 patients with type 3 ischemia (impaired CBF, impaired CVR). The plaque components were categorized into fibrous (4 patients), lipid-rich (14 patients), and intraplaque hemorrhage (IPH; 20 patients). Of the patients with fibrous plaque, 2 had border-zone and 2 had mixed-pattern infarcts. Of the patients with lipid-rich plaque, 7 had cortical and 6 had mixed-pattern infarcts. Of patients with intraplaque hemorrhage, 11 had cortical and 9 had mixed-pattern infarcts.

CONCLUSION:

Cortical infarction occurs as a result of vulnerable plaque. Reduced cerebral perfusion induces border-zone infarction. Both factors are implicated in mixed-pattern infarction. Developments in noninvasive diagnostic modalities allow us to explore the mechanisms behind acute cerebrovascular syndrome in carotid artery stenosis and to determine the ideal therapies.

Does preoperative measurement of cerebral blood flow with acetazolamide challenge in addition to preoperative measurement of cerebral blood flow at the resting state increase the predictive accuracy of development of cerebral hyperperfusion after carotid endarterectomy? Results from 500 cases with brain perfusion single-photon emission computed tomography study

The purpose of the present study was to determine whether preoperative measurement of cerebral blood flow (CBF) with acetazolamide in addition to preoperative measurement of CBF at the resting state increases the predictive accuracy of development of cerebral hyperperfusion after carotid endarterectomy (CEA). CBF at the resting state and cerebrovascular reactivity (CVR) to acetazolamide were quantitatively assessed using N-isopropyl-p-[¹²³I]-iodoamphetamine (IMP)-autoradiography method with single-photon emission computed tomography (SPECT) before CEA in 500 patients with ipsilateral internal carotid artery stenosis (≥ 70%). CBF measurement using ¹²³I-IMP SPECT was also performed immediately and 3 days after CEA. A region of interest (ROI) was automatically placed in the middle cerebral artery territory in the affected cerebral hemisphere using a three-dimensional stereotactic ROI template. Preoperative decreases in CBF at the resting state [95% confidence intervals (CIs), 0.855 to 0.967; P = 0.0023] and preoperative decreases in CVR to acetazolamide (95% CIs, 0.844 to 0.912; P < 0.0001) were significant independent predictors of post-CEA hyperperfusion. The area under the receiver operating characteristic curve for prediction of the development of post-CEA hyperperfusion was significantly greater for CVR to acetazolamide than for CBF at the resting state (difference between areas, 0.173; P < 0.0001). Sensitivity, specificity, and positive- and negative-predictive values for the prediction of the development of post-CEA hyperperfusion were significantly greater for CVR to acetazolamide than for CBF at the resting state (P < 0.05, respectively). The present study demonstrated that preoperative measurement of CBF with acetazolamide in addition to preoperative measurement of CBF at the resting state increases the predictive accuracy of the development of post-CEA hyperperfusion.

Intraoperative management of carotid endarterectomy

First reports on surgical treatment of cerebrovascular atherosclerosis date to the early 1950s. With advancements in surgical technique, carotid endarterectomy (CEA) has become the treatment of choice for patients with both symptomatic and asymptomatic severe carotid stenosis. Given the benefits that surgery offers beyond medical management, the number of CEA procedures continues to increase. The intraoperative management of patients undergoing CEA is challenging because of the combination of patient and surgical factors. This article explores and reviews the literature on anesthetic management and considerations of patients undergoing CEA.

Systematic review of near-infrared spectroscopy determined cerebral oxygenation during non-cardiac surgery

Near-infrared spectroscopy (NIRS) is used to monitor regional cerebral oxygenation (rScO₂) during cardiac surgery but is less established during non-cardiac surgery. This systematic review aimed (i) to determine the non-cardiac surgical procedures that provoke a reduction in rScO₂ and (ii) to evaluate whether an intraoperative reduction in rScO₂ influences postoperative outcome. The PubMed and Embase database were searched from inception until April 30, 2013 and inclusion criteria were intraoperative NIRS determined rScO₂ in adult patients undergoing non-cardiac surgery. The type of surgery and number of patients included were recorded. There was included 113 articles and evidence suggests that rScO₂ is reduced during thoracic surgery involving single lung ventilation, major abdominal surgery, hip surgery, and laparoscopic surgery with the patient placed in anti-Tredelenburg's position. Shoulder arthroscopy in the beach chair and carotid endarterectomy with clamped internal carotid artery (ICA) also cause pronounced cerebral desaturation. A >20% reduction in rScO₂ coincides with indices of regional and global cerebral ischemia during carotid endarterectomy. Following thoracic surgery, major orthopedic, and abdominal surgery the occurrence of postoperative cognitive dysfunction (POCD) might be related to intraoperative cerebral desaturation. In conclusion, certain non-cardiac surgical procedures is associated with an increased risk for the occurrence of rScO₂. Evidence for an association between cerebral desaturation and postoperative outcome parameters other than cognitive dysfunction needs to be established.

Cerebral hyperperfusion syndrome following the excision of a mycotic aneurysm with superficial temporal artery-to-middle cerebral artery bypass: case report

The authors report a rare case of cerebral hyperperfusion syndrome (HPS) following the excision of a mycotic aneurysm with superficial temporal artery-to-middle cerebral artery (STA-MCA) bypass. A 74-year-old woman with infective endocarditis presented with progressive cerebral infarction and subarachnoid hemorrhage due to a mycotic aneurysm, which was excised with a STA-MCA bypass. Postoperatively, the patient developed HPS that was considered to be exacerbated by a previous ischemic event. Therefore, cerebral hemodynamics should be evaluated before bypass surgery to prevent subsequent hyperperfusion.

Post-carotid endarterectomy cerebral hyperperfusion syndrome : is it preventable by strict blood pressure control?

Objective

Cerebral hyperperfusion syndrome (CHS) is a serious complication after carotid endarterectomy (CEA). However, the prevalence of CHS has decreased as techniques have improved. This study evaluates the role of strict blood pressure (BP) control for the prevention of CHS.

Methods

All 18 patients who received CEA from February 2009 through November 2012 were retrospectively reviewed. All patients were routinely managed in an intensive care unit by a same protocol. The cerebral perfusion state was evaluated on the basis of the regional cerebral blood flow (rCBF) study by perfusion computed tomography (pCT) and mean velocity by transcranial doppler (TCD). BP was strictly controlled (<140/90 mm Hg) for 7 days. When either post-CEA hyperperfusion (>100% increase in the rCBF by pCT or in the mean velocity by TCD compared with preoperative values) or CHS was detected, BP was maintained below 120/80 mm Hg.

Results

TCD and pCT data on the patients were analyzed. Ipsilateral rCBF was significantly increased after CEA in the pCT (p=0.049). Post-CEA hyperperfusion was observed in 3 patients (18.7%) in the pCT and 2 patients (12.5%) in the TCD study. No patients developed clinical CHS for one month after CEA. Furthermore, no patients developed additional neurological deficits related to postoperative cerebrovascular complications.

Conclusion

Intensive care with strict BP control (<140/90 mm Hg) achieved a low prevalence of post-CEA hyperperfusion and prevented CHS. This study suggests that intensive care with strict BP control can prevent the prevalence of post-CEA CHS.

Hyperperfusion syndrome after stent/coiling of a ruptured carotid bifurcation aneurysm

The authors report a syndrome of regional, symptomatic cerebral hyperperfusion, and edema mimicking infarction in a 54-year-old woman following coiling of a ruptured right carotid bifurcation aneurysm and stenting of the right middle cerebral artery. The patient presented with a Hunt and Hess grade III subarachnoid hemorrhage 7 days after developing thunderclap headache. She underwent successful coiling under general anesthesia of the 1.6 × 1.5 × 1.6 cm aneurysm, but immediately after the coil was placed occlusion of the proximal M1 segment was developed. This occlusion was stented after ~5-min delay, and flow restored without angiographic evidence of distal emboli. Following the procedure, she was extubated and noted to have left hemiparesis, neglect, and mutism without a CT correlate. Cerebral infarction was suspected, but urgent repeat angiography demonstrated patent cerebral vasculature. On the following day, symptoms persisted, and non-contrast head CT now showed cerebral edema localized to the right middle cerebral artery territory mimicking subacute infarction. CT perfusion imaging and angiography showed a widely patent MCA circulation, and suggested a regional hyperperfusion syndrome. The blood pressure was incrementally lowered, with rapid and sustained neurological improvement. Hyperperfusion events following aneurysm repair and related circumstances are reviewed.

Cerebral hemodynamics and baroreflex sensitivity after carotid artery stenting

OBJECTIVES

The long-term hemodynamic effects of carotid angioplasty and stenting (CAS) are unclear. We performed a longitudinal study to investigate the variations in cerebral hemodynamics in patients undergoing CAS.

MATERIALS AND METHODS

We performed prospective evaluation of 63 symptomatic male patients (19 patients had transient ischemic attack and 44 had minor stroke; mean age: 77.3 ± 6.3 years [range: 51-86]). The mean blood flow velocities (MBFV) and pulsatility index (PI) of the middle cerebral arteries (MCA) on both sides were evaluated using transcranial color-coded Doppler (TCCD) ultrasonography. Cardiac autonomic activities were evaluated by measuring baroreflex sensitivity (BRS). All parameters were measured at baseline prior to CAS and at 1, 3, 6, and 12 months after CAS.

RESULTS

The preoperative MBFV and PI of the ipsilateral MCA were significantly lower than those of the contralateral side. However, after CAS, MBFV in the ipsilateral MCA increased significantly until 2 weeks after stenting, after which the MBFV gradually decreased and remained stable for 1 year after CAS. Further, we observed a nonsignificant increase in MBFV in the contralateral MCA after CAS. In contrast to the MBFV, the BRS values decreased significantly 1 month after stenting and returned to baseline levels 6 months after CAS.

CONCLUSIONS

Patients with CAS showed improved global cerebral hemodynamic status. However, the BRS did not normalize initially, and baseline value was achieved at 6 months after stenting.

Effect of propofol on hypoxia re-oxygenation induced neuronal cell damage in vitro*

Propofol may protect neuronal cells from hypoxia re-oxygenation injury, possibly via an antioxidant actions under hypoxic conditions. This study investigated the molecular effects of propofol on hypoxia-induced cell damage using a neuronal cell line. Cultured human IMR-32 cells were exposed to propofol (30 μm) and biochemical and molecular approaches were used to assess cellular effects. Propofol significantly reduced hypoxia-mediated increases in lactate dehydrogenase, a marker of cell damage (mean (SD) for normoxia: 0.39 (0.07) a.u.; hypoxia: 0.78 (0.21) a.u.; hypoxia+propofol: 0.44 (0.17) a.u.; normoxia vs hypoxia, p<0.05; hypoxia vs hypoxia+propofol, p<0.05), reactive oxygen species and hydrogen peroxide. Propofol also diminished the morphological signs of cell damage. Increased amounts of catalase, which degrades hydrogen peroxide, were detected under hypoxic conditions. Propofol decreased the amount of catalase produced, but increased its enzymatic activity. Propofol protects neuronal cells from hypoxia re-oxygenation injury, possibly via a combined direct antioxidant effect along with induced cellular antioxidant mechanisms.

Predictors and clinical features of postoperative hyperperfusion after surgical revascularization for moyamoya disease: a serial single photon emission CT/positron emission tomography study

BACKGROUND AND PURPOSE

Clinical features and pathophysiology of postoperative hyperperfusion in moyamoya disease are still unclear. This study was aimed to clarify the incidence and time course of postoperative hyperperfusion and to determine the independent predictors of postoperative hyperperfusion in moyamoya disease.

METHODS

This prospective study included 41 patients who underwent surgical revascularization for moyamoya disease. Using (15)O-gas positron emission tomography, hemodynamic and metabolic parameters were quantified before surgery. Using single photon emission computed tomography, cerebral blood flow was serially measured just after surgery and on 2 and 7 days postsurgery. A multivariate logistic regression analysis was conducted to test the effect of multiple variables on postoperative hyperperfusion.

RESULTS

Postoperative hyperperfusion was observed in 29 (50.0%) of 58 operated hemispheres. The incidence of both radiological and symptomatic hyperperfusion was significantly higher in adult patients than in pediatric ones (P=0.026 and P=0.0037, respectively). Hyperperfusion just after surgery more often led to subsequent neurological deficits (P=0.033). A multivariate analysis revealed that preoperative cerebral blood volume increase was an independent predictor of both radiological and symptomatic hyperperfusion after surgery in adult moyamoya disease (OR, 6.6 and 12.3, respectively).

CONCLUSIONS

Postoperative hyperperfusion after surgical revascularization is not rare in moyamoya disease. Adult patients with a cerebral blood volume increase may be at high risk for radiological and symptomatic hyperperfusion after surgery. Careful perioperative management would reduce surgical complications and improve long-term outcome in moyamoya disease.

Ischemic events due to intraoperative microemboli developing in the cerebral hemisphere contralateral to carotid endarterectomy in a patient with preoperative cerebral hemodynamic impairment

A 74-year-old man with a history of asymptomatic right internal carotid artery (ICA) occlusion experienced amaurosis fugax in the left eye. Angiography showed left cervical ICA stenosis in addition to right cervical ICA occlusion. The right anterior and middle cerebral artery (MCA) territories were perfused from the left ICA via the anterior communicating artery. Brain perfusion single-photon emission computed tomography revealed reduced cerebral blood flow and reduced cerebrovascular reactivity to acetazolamide only in the right cerebral hemisphere. The patient underwent left carotid endarterectomy (CEA). Transcranial Doppler monitoring showed microembolic signals in the left MCA during dissection of the left ICA, but intraoperative monitoring suggested absence of global hypoperfusion or ischemia in the bilateral cerebral hemispheres during left ICA clamping. Transient and slight motor weakness of the left upper extremity was noted on recovery from anesthesia. Diffusion-weighted magnetic resonance imaging demonstrated the development of new spotty ischemic lesions only in the right cerebral hemisphere. The present case suggests that intraoperative cerebral embolism causing postoperative neurological deficits can develop exclusively in the cerebral hemisphere contralateral to CEA if the hemisphere has preoperative hemodynamic impairment and collateral circulation via the anterior communicating artery from the ICA ipsilateral to CEA.

Intraprocedural prediction of hemorrhagic cerebral hyperperfusion syndrome after carotid artery stenting

Hyperperfusion syndrome (HPS) is a rare but severe complication after carotid artery stenting (CAS). Reliable methods for predicting HPS remain to be developed. We aimed to establish a predictive value of hemorrhagic HPS after CAS. Our retrospective study included 136 consecutive patients who had undergone CAS. We determined the cerebral circulation time (CCT) by measuring the interval between the point of maximal opacification of the terminal portion of the internal carotid artery and the cortical vein. We calculated intraprocedural CCT changes (ΔCCT) by subtracting postprocedural CCT values from preprocedural CCT values. The mean ΔCCT was 0.9 ± 0.9 seconds; 3 patients (2.2%) with prolonged ΔCCT (2.7, 5.4, and 5.8 seconds) developed HPS. The cutoff time of 2.7 seconds predicted hemorrhagic HPS retrospectively with 100% sensitivity and 99% specificity. Our findings suggest that post-CAS HPS can be predicted by using the ΔCCT value obtained by intraprocedural digital subtraction angiography. Patients with a ΔCCT >2.7 seconds require careful intensive hemodynamic and neurologic monitoring after CAS.

Clinical application of arterial spin-labeling MR imaging in patients with carotid stenosis: quantitative comparative study with single-photon emission CT

BACKGROUND AND PURPOSE

Arterial spin-labeling is an emerging technique for noninvasive measurement of cerebral perfusion, but concerns remain regarding the reliability of CBF quantification and clinical applications. Recently, an ASL implementation called QUASAR was proposed, and it was shown to have good reproducibility of CBF assessment in healthy volunteers. This study aimed to determine the utility of QUASAR for CBF assessment in patients with cerebrovascular diseases.

MATERIALS AND METHODS

Twenty patients with carotid stenosis underwent CBF quantification by ASL (QUASAR) within 3 days of performance of (123)I-iodoamphetamine-SPECT. CVR to acetazolamide also was assessed by ASL and SPECT. In surgically treated patients, the respective scans before and after the procedures were compared.

RESULTS

Regional CBF and CVR values measured by ASL were significantly correlated and agreed with those measured by SPECT (r(s) = 0.92 and 0.88, respectively). A Bland-Altman plot demonstrated good agreement between 2 methods in terms of CBF quantification. Furthermore, ASL could detect pathologic states such as hypoperfusion, impaired vasoreactivity, and postoperative hyperperfusion, equivalent to SPECT. However, ASL tended to overestimate CBF values especially in high-perfusion regions.

CONCLUSIONS

ASL perfusion MR imaging is clinically applicable and can be an alternative method for CBF assessment in patients with cerebrovascular diseases.

Significance of Focal Cerebral Hyperperfusion as a Cause of Transient Neurologic Deterioration After Extracranial-Intracranial Bypass for Moyamoya Disease: Comparative Study With Non-Moyamoya Patients Using N-Isopropyl-p-[123I]Iodoamphetamine Single-Photon Emission Computed Tomography

BACKGROUND:

Superficial temporal artery-middle cerebral artery (STA-MCA) anastomosis prevents cerebral ischemic attack by improving cerebral blood flow in patients with occlusive cerebrovascular disease and hemodynamic compromise. Recent evidence suggests that focal cerebral hyperperfusion is a potential complication of this procedure for moyamoya disease.

OBJECTIVE:

To clarify the exact differences in the incidence and clinical manifestations of this phenomenon between patients with and without moyamoya disease.

METHODS:

N-isopropyl-p-[123I]iodoamphetamine single-photon emission computed tomography was performed 1 and 7 days after STA-MCA anastomosis on 121 hemispheres from 86 consecutive patients with moyamoya disease (2–67 years of age; mean, 34.3 years) and on 28 hemispheres from 28 non-moyamoya patients (12–67 years of age; mean, 56.5 years). The incidence of symptomatic hyperperfusion, defined as a significant focal increase in cerebral blood flow at the site of the anastomosis that is responsible for the apparent neurological signs, was compared between groups.

RESULTS:

Symptomatic cerebral hyperperfusion including mild focal neurological signs was seen in 25 patients with moyamoya disease (26 hemispheres, 21.5%) but in none of the patients without moyamoya disease (P = .0069). Multivariate analysis revealed that moyamoya disease was significantly associated with the development of symptomatic cerebral hyperperfusion (P = .0008). All patients with symptomatic hyperperfusion were relieved by intensive blood pressure control, and no patients suffered from permanent neurological deficit caused by hyperperfusion.

CONCLUSION:

Symptomatic cerebral hyperperfusion is a potential complication of STA-MCA anastomosis, especially in patients with moyamoya disease. Accurate diagnosis and adequate management of hyperperfusion are recommended, especially in patients with moyamoya disease.

Intraprocedural changes in angiographic cerebral circulation time predict cerebral blood flow after carotid artery stenting

Changes in the cerebral blood flow (CBF) are important for planning postoperative care in patients treated by carotid artery stenting (CAS). The relationship between intraprocedural changes in the angiographic cerebral circulation time (CCT) and perioperative CBF changes were retrospectively studied in 49 CAS procedures performed in 46 patients with carotid artery stenosis. The CCT, defined as the interval between the timing of maximal opacification at the terminal portion of the internal carotid artery and at the cortical vein, was determined by referring to time-density curves of data obtained from routine intraprocedural digital subtraction angiography. The intraoperative change in CCT (Delta CCT) was calculated for each of the 49 procedures. CBF studies, using dynamic perfusion computed tomography, were performed 10-2 days before and 2-4 days after CAS. Perioperative changes in the ratio of the CBF in the territory of the middle cerebral artery on the affected side to CBF on the contralateral side (%CBF) were calculated by subtracting pre- from postoperative %CBF (Delta%CBF) and the correlation between Delta CCT and Delta%CBF was evaluated. Mean CCT was shortened by 1.1 seconds from 5.3 to 4.2 seconds after CAS. Mean %CBF increased by 11.9% from 91.8% to 103.7% after the procedure. Delta CCT and Delta%CBF showed a significant positive correlation (r = 0.61, p = 0.008). Intraprocedural changes in angiographic CCT are predictive of postoperative CBF in patients with CAS.