Incidence Of Cerebral Hyperperfusion Syndrome Research Articles

Risk Factors for Cerebral Hyperperfusion Syndrome After Combined Revascularization in Adult Patients with Moyamoya Disease.

Cerebral hyperperfusion syndrome (CHS) is known as a complication after bypass surgery for Moyamoya disease (MMD). However, the incidence of CHS has not been accurately reported, and there is no consensus on the risk factors associated with it. The aim of this study was to determine the risk factors associated with postoperative CHS after surgical combined revascularization used to treat adult patients with MMD. To assess the frequency and characteristics of CHS in patients with MMD after revascularization operations. Patients who received combined revascularization from Jan 2021 to Nov 2022 were retrospectively reviewed. Preoperative clinical characteristics and radiographic features were recorded. Postoperative CHS after surgery were examined. Multivariate logistic regression analyses were performed to identify the risk factors for CHS. A total of 133 patients (141 hemispheres) were included in this study. Postoperative CHS were observed in 28 hemispheres (19.8%), including focal cerebral hyperperfusion syndrome (FCHS) in 20 hemispheres (14.2%), hemorrhage in 4 (2.8%) hemispheres, seizures in 4 (2.8%) hemispheres. The results of multivariate logistic regression analysis indicated that preoperative hypertension (OR 4.705, 95% CI 1.323 ~ 12.554, p = 0.014), cerebral hemorrhage onset (OR 5.390, 95% CI 1.408 ~ 20.642, p = 0.014) and higher Hct level (OR 1.171, 95% CI 1.051 ~ 1.305, p = 0.004) were significantly associated with CHS after combined revascularization. Preoperative hypertension, cerebral hemorrhage onset, and higher Hct level were independent risk factors for CHS after combined revascularization.

Clinical effect of a modified superficial temporal artery-middle cerebral artery bypass surgery in Moyamoya disease treatment

BackgroundCerebral extracranial-intracranial (EC-IC) revascularization technique (superficial temporal artery-middle cerebral artery (STA-MCA) bypass grafting) has become the preferred surgical method for the treatment of Moyamoya disease (MMD). We attempted to completely free the two branches of the superficial temporal artery without disconnection. Extracranial and intracranial blood flow reconstruction were then modified by selectively performing a direct bypass technique on one branch and a patch fusion technique on the other of the STA based on the blood flow and the vascular diameter of the intracranial surface blood vessels.MethodsA series of modified STA-MCA bypass surgeries performed consecutively between March 2022 and March 2023 were reviewed and compared to conventional combined bypass surgeries performed during the same period. The following information was collected from all enrolled patients: demographic characteristics, clinical symptoms, and preoperative and postoperative imaging, including Suzuki stage and Matsushima grade. The modified Rankin scale (mRS) was used to assess the changes in neurological status before and after surgery.ResultsA total of 41 patients with Moyamoya disease (MMD) who underwent cerebral revascularization were included in this study, of which 30 were conventional revascularization and 11 were modified revascularization. The mean age was 49.91 years, and 18 (43.9%) of the patients were women. The modified group had a lower incidence of cerebral hyperperfusion syndrome (18.2%) than the conventional group (23.3%). After at least 3 months of follow-up, the bypass patency rate remained 100% in the modified group and 93.3% in the conventional group. All patients in the modified group achieved a better Matsushima grade (A + B), with six (54.5%) having an A and five (45.5%) having a B. In contrast, four patients (13.3%) in the conventional group had a Matsushima grade of C. In all, 72.8% of the modified group had postoperative mRS scores of 0 and 1, which was higher than that of the traditional group (63.3%).ConclusionThe improved STA-MCA bypass could provide blood flow to multiple cerebral ischemic areas, reduce excessive blood perfusion, and ensure blood supply to the scalp, with lower complications and better clinical benefits than the traditional combined bypass.

Risk Factors for Cerebral Hyperperfusion Syndrome following Carotid Revascularization

Cerebral hyperperfusion syndrome (CHS) is a rare but known complication of carotid revascularization that can result in severe postoperative disability and death. CHS is a well-described sequela of carotid endarterectomy (CEA) and, more recently, of transfemoral carotid artery stenting (TFCAS), but its incidence after transcarotid artery revascularization (TCAR) has not been delineated. The aims of this study were to determine the impact of procedure type (CEA versus TCAR versus TFCAS) on the development of CHS as well as to identify perioperative risk factors associated with CHS. The Society for Vascular Surgery Vascular Quality Initiative was queried for patients aged ≥18years who underwent CEA, TCAR, or TFCAS from 2015-2021. Emergent procedures were excluded. The primary outcome was postoperative development of CHS, defined as the presence of postoperative seizures, intracerebral hemorrhage due to hyperperfusion, or both. Bivariate and multivariable logistic regression analyses were performed to identify factors associated with CHS. 156,003 procedures were included (72.7% CEA, 12.4% TCAR, and 14.9% TFCAS). The incidence of CHS after CEA, TCAR, and TFCAS were 0.15%, 0.18%, and 0.53%, respectively. There was no significant difference in risk of CHS after TFCAS compared to CEA (odds ratio [OR]: 1.21; 95% confidence interval [CI] 0.76-1.92; P=0.416), nor was there a difference between TCAR and CEA (OR: 0.91; 95% CI 0.57-1.45; P=0.691). Perioperative risk factors associated with an increased risk of CHS included previous history of transient ischemic attack or stroke (OR: 2.50; 95% CI 1.69-3.68; P<0.0001), necessity for urgent intervention within 48hr (OR: 2.03; 95% CI 1.43-2.89; P<0.0001), treatment of a total occlusion (OR: 3.80; 95% CI 1.16-12.47; P=0.028), and need for postoperative intravenous blood pressure medication (OR: 5.45; 95% CI 3.97-7.48; P<0.0001). Age, preoperative hypertension, degree of ipsilateral stenosis less than or equal to 99%, and history of prior carotid procedures were not statistically associated with an increased risk of CHS. Discharging patients on an angiotensin-converting enzyme inhibitor or angiotensin II receptor blocker was associated with a decreased risk of developing CHS (OR: 0.47; 95% CI 0.34-0.65; P<0.0001). Compared with CEA, TCAR and TFCAS were not statistically associated with an increased risk of postoperative CHS. Patients with a previous history of transient ischemic attack or stroke, who require urgent intervention or postoperative intravenous blood pressure medication, or who are treated for a total occlusion are at a higher risk of developing CHS. Using an angiotensin-converting enzyme inhibitor/angiotensin II receptor blocker on discharge appears to be protective against CHS and should be considered for the highest risk patients.

A flow self-regulating superficial temporal artery-middle cerebral artery bypass based on side-to-side anastomosis for adult patients with moyamoya disease.

Side-to-side (S-S) superficial temporal artery-middle cerebral artery (STA-MCA) bypass was reportedly used to treat a special moyamoya disease (MMD) patient with collaterals arising from the donor STA. However, the S-S technique is not routinely performed to date, and its benefits are still unknown for adult MMD. The purpose of this study was to investigate the possibility of routine use of the S-S technique for adult MMD. The authors retrospectively analyzed the clinical data of 50 adult patients (65 hemispheres, including 30 in the end-to-side [E-S] group and 35 in the S-S group) with MMD who underwent STA-MCA bypass. The patient demographic characteristics, clinical courses, technical details, intraoperative blood flow data, postoperative and preoperative relative cerebral blood flow (rCBF) values, modified Rankin Scale (mRS) scores, and short-term revascularization results were compared between the 2 groups. There were no significant differences observed in terms of the baseline characteristics, bypass patency rates, postoperative/preoperative rCBF values, incidence of cerebral hyperperfusion syndrome (CHS), mRS scores, and short-term revascularization results between the 2 groups (all p > 0.05). Intraoperative blood flow analysis showed that the increase of STA flow in the E-S group was significantly higher than that of proximal STA flow in the S-S group (p = 0.008). Although the increases of proximal and distal recipient flow in the E-S group seemed greater than those in the S-S group, the results were not statistically significant (p = 0.086 for proximal flow and p = 0.076 for distal flow). CHS symptoms in the S-S group were milder and with much shorter duration. The follow-up angiographic data of the representative case demonstrated that both frontal and parietal STA branches and the occipital artery participated in postoperative collateralization. S-S anastomosis can achieve comparable clinical effects to standard E-S construction. S-S anastomosis used in adult MMD demonstrated mild CHS symptoms with short duration and had the potential to arouse all scalp arteries as donor sources for revascularization through the intact distal STA branch via flow self-regulation.

Matching Selection of Donor-Recipient Vessels in Revascularization Surgery Effectively Reduce the Incidence of Postoperative Hyperperfusion Syndrome in Adult Moyamoya Disease: A Retrospective Comparison Study

Introduction: Cerebral hyperperfusion syndrome (CHS) is one of the most serious complications after revascularization surgery in patients with moyamoya disease (MMD). However, there are few effective measures to prevent the occurrence of CHS. Objective: The present study aims to examine the effect of the method about matching selection of donor-recipient vessels during revascularization surgery on the incidence of postoperative CHS in adult MMD patients. Methods: 216 Chinese adult patients with MMD received surgery treatment between January 2018 and December 2019 in our hospital were enrolled in this study. 191 out of 216 patients were included in this study. Matching selection method was defined as follows: (1) blood flow: the direction of blood flow and speed of the donor artery and potential receptor arteries were measured by flow 800 indocyanine green video angiography; (2) vascular diameter: the diameters of the donor artery and potential receptor arteries by a miniature ruler. Only the artery with antegrade flow and with smallest difference in flow speed and diameter with the donor artery will be selected as the receptor artery to perform anastomosis. Matching selection was performed from January 2019. Digital subtraction angiography was performed in all patients for initial MMD diagnosis. Perioperative cerebral perfusion and related clinical symptoms were monitored. Clinical characteristics, contralateral progression, and risk factors were reviewed. The incidence of CHS and the correlation of CHS with baseline characteristics or clinical conditions were analyzed. Results: Of these 191 patients, 82 patients received matching selection of donor-recipient vessels during revascularization surgery and 109 patients without. The postoperative CHS incidence in the matching group was 3.66%, which was much lower than that in the nonmatching group (15.60%). Multivariate analysis did not reveal a significant risk factor between the progression group and the nonprogression group. Correlation analysis revealed only the matching selection method was significantly associated with the reduced postoperative CHS incidence in MMD patients. Conclusions: The matching selection of donor-recipient vessels during revascularization surgery effectively reduces the incidence of postoperative CHS in adult patients with MMD.

Comparative Effectiveness of Preventive and Treatment Interventions for Cerebral Hyperperfusion Syndrome Following Bypass Surgery

Abstract INTRODUCTION Although cerebral hyperperfusion syndrome (CHS) remains a major complication of bypass surgery that can lead to severe neurological morbidity and mortality, data regarding its prevention and treatment have not been assorted until date. Thus, we systematically reviewed the literature, to assess available data and evaluate whether any conclusions can be drawn regarding the effectiveness of utilized interventions on either preventing or treating bypass related CHS. METHODS We systematically reviewed PubMed &amp; Cochrane Library from September 2008 to September 2018 according to PRISMA, to collect data regarding the effectiveness of pharmacologic interventions on the prevention (PRE) and treatment (TRE) of bypass-related CHS. We categorized interventions regarding their class of drugs and their combinations and calculated overall pooled estimates of the proportions of CHS development or improvement through random-effects meta-analyses of proportions using a Freeman-Tukey double arcsine transformation. RESULTS Our search yielded 646 studies of which 40 fulfilled inclusion criteria. Meta-analysis of PRE included 23 studies/2041 cases. In group [A] (BP control) 202 out of 1174 pretreated cases developed CHS (23.3% pooled estimate; 95% CI 9.9-39.4), in group [B] (BP control + Free Radical Scavenger (FRS)) 10/263 pretreated cases developed CHS (0.3%; 95% CI 0.0-14.1), in group [C] (BP control + antiplatelet) 22/204 pretreated cases developed CHS (10.3%; 95% CI 5.1-16.7), and in group [D] (BP control + Postoperative sedation) 29/400 pretreated cases developed CHS (6.8%; 95% CI 4.4-9.6)]. Meta-analysis of TRE included 29 studies/144 cases that developed CHS. Pooled estimates of improvement ranged from 92.1% to 100.0%. CONCLUSION Our data suggest that BP control alone as a pretreatment has not been proven effective in preventing CHS. However, BP control along with either postoperative sedation or an FRS or an antiplatelet agent seem to reduce the incidence of CHS. Once CHS has developed, BP control and/or FRS administration may ameliorate symptoms.

Abstract WP134: Decreased Flow Velocities After General Anesthesia Before Carotid Endarterctomy Are Not Associated with Cerebral Hyperperfusion Syndrome or Perioperative Cerebral Infarction

Introduction: Cerebral Hyperperfusion Syndrome (CHS) is a life threatening complication in about 3% of patients following carotid endarterectomy (CEA). There is a concern that baseline flow velocities typically decrease after general anesthesia (GA) may predispose patients to CHS and other perioperative adverse events. Hypothesis: Patients with decreased flow velocity after GA are at increased risk for CHS using ultrasonographic and clinical diagnostic criteria. Methods: We retrospectively evaluated 920 patients who received CEA from 2006 to 2016 at a major hospital in China. Middle cerebral artery blood flow velocities were measured when patients were awake and after induction of the GA. Ultrasonographic diagnostic criterion of CHS was “100% increase in flow velocity by TCD from the baseline to post-CEA”. Patients were classified into two groups: NORMAL group if flow velocity decreased &lt;30% and LOW group if decreased &gt;=30%. The occurrences of CHS by ultrasonongraphic and clinical criteria, perioperative cerebral infarction were compared using Chi-square test. Results: 399 (43.4%) were classified as LOW and 522 (56.7%) patients as NORMAL. In the LOW group, there were more patients with diabetes, less patients with ICA severe stenosis and opening of anterior/posterior communicating artery. Occurrence of CHS per ultrasonographic criteria was higher in the LOW group (21.3% vs. 15.7%, P=0.03), but similar for clinical CHS criteria group (3.2%, vs 2.1%, p=0.28) and for frequency of perioperative cerebral infarction (5.8% vs.5.0%, p=0.60). Conclusion: Although patients with decreased flow velocities post-GA were more likely to meet ultrasonographic criteria for CHS, there were no differences in clinical CHS criteria. Our results suggest decreased flow velocities post-GA may not associated with incidence of CHS.

Abstract TP123: Efficacy of Staged Angioplasty to Prevent Cerebral Hyperperfusion Syndrome After Endovascular Revascularization for Carotid Artery Stenosis

Background and aim: Cerebral hyperperfusion syndrome (CHS) including intracranial hemorrhage (ICH) is a serious complication after carotid artery stenting (CAS). Staged angioplasty (SAP), undersized-balloon angioplasty followed by delayed CAS, was reported to be a potential preventable method against CHS. The aim of this study was to clarify the efficacy of SAP to prevent CHS after endovascular carotid revascularization for high-risk patients of CHS. Methods: The STOP CHS study is a multicenter, retrospective study which registered 535 high-risk patients of CHS from 45 Japanese centers, who underwent regular CAS, SAP or angioplasty performed by board-certified neurointerventionists between October 2007 and March 2014. Selection of high-risk patients of CHS was based on imaging tests, such as single-photon emission computed tomography with acetazolamide. We investigated the cumulative periprocedural rates of CHS, ICH and major adverse event (MAE: stroke, myocardial infarction and death) of patients scheduled for regular CAS or SAP (intention-to-treat [ITT] population) and the relationship between SAP and the cumulative incidence of CHS in ITT and as-treated (AT) populations (patients who underwent regular CAS or SAP). Results: A total of 525 patients (532 lesions, 74 women, 72.5±7.5 years old) was included. Angiographic stenosis was 86.2±9.2% and 337 lesions were symptomatic. Scheduled procedures were regular CAS in 419 lesions and SAP in 113 lesions, and final procedures were regular CAS in 428 lesions, SAP in 102 lesions and angioplasty in 2 lesions. The cumulative event rates were CHS in 9.2%, ICH in 4.3% and MAE in 11.5%, and these were higher in patients scheduled for regular CAS than in patients scheduled for SAP(10.5 % vs 4.4%, 5.3% vs 0.9% and 12.9% vs 6.2% with each p-value &lt;0.05, respectively). After multivariate adjustment, schedule for SAP was negatively related to the cumulative incidence of CHS (OR, 0.25; 95%CI, 0.09-0.73). Same applied to implementation of SAP in AT population (OR, 0.28; 95%CI, 0.10-0.82). Conclusion: The cumulative periprocedural event rates of high-risk patients of CHS scheduled for regular CAS or SAP were actually high. SAP was a negative predictor of CHS in both ITT and AT populations.

Intraoperative dexmedetomidine and postoperative cerebral hyperperfusion syndrome in patients who underwent superficial temporal artery-middle cerebral artery anastomosis for moyamoya disease: A retrospective observational study.

Dexmedetomidine, a selective α2-agonist, reduces cerebral blood flow and has neuroprotective effects against cerebral ischemia/reperfusion injury in experimental animals. We examined whether intraoperative dexmedetomidine would reduce the incidence of postoperative cerebral hyperperfusion syndrome (CHS) after superficial temporal artery-middle cerebral artery (STA-MCA) anastomosis in patients with moyamoya disease.The electronic medical records of 117 moyamoya patients who underwent STA-MCA anastomosis were reviewed retrospectively. The patients were divided into 2 groups: 48 patients received intraoperative dexmedetomidine (Group D), while 69 patients did not (Group ND). The incidence (primary outcome), onset, and duration of postoperative CHS were noted.The incidence of postoperative CHS was 45.8% and 40.6% in groups D and ND, respectively (P = 0.708). The duration of postoperative CHS was shorter in group D than in group ND (median [Q1–Q3], 5 [3–7] vs 8 [5–10] days, P = 0.021). There was no significant difference in the onset of CHS between group D and group ND (0 [0–2] vs 1 [0–3] days, P = 0.226).In conclusion, intraoperative dexmedetomidine did not reduce the incidence of postoperative CHS, although it reduced the duration of CHS, in patients who had undergone direct revascularization surgery for moyamoya disease.

Usefulness of Early Stenting for Symptomatic Extracranial Carotid Stenosis

While carotid angioplasty and stenting (CAS) have become an established procedure, outcomes of early CAS for symptomatic extracranial carotid stenosis (SECS) remain poorly understood. The present study aimed at determining the effectiveness of early CAS in SECS. Herein, 224 SECS patients underwent elective CAS between January 2008 and June 2015. The study population was stratified based on the time from symptom onset to the procedure (early CAS group: within 14 days; delayed CAS group: later than 14 days). Subgroup analysis (chi-square test, Mantel-Haenszel chi-square test, and analysis of covariance) evaluated the demographics, incidence of periprocedural thromboembolic complications, cerebral hyperperfusion syndrome (CHS), intracranial bleeding, and treatment outcomes on the modified Rankin Scale (mRS). Symptomatic thromboembolic complications and CHS were noted in 2.68% and 0.89% of patients, respectively. The initial National Institutes of Health Stroke Scale (NIHSS) score was significantly higher in patients who underwent early CAS than in those who underwent delayed CAS (2.50 ± 3.97 vs. 0.97 ± 2.08, P= 0.001). After adjusting for age, duration of preprocedural dual antiplatelet therapy, initial NIHSS score, and preprocedural NIHSS score, the groups did not differ significantly regarding the incidence of symptomatic thromboembolic complications (P= 0.195), incidence of CHS (P= 0.950), incidence of intracranial bleeding (P = 0.970), 30-day mRS score (P= 0.124), and mRS score at final follow-up (P= 0.132). For SECS patients who cannot undergo early carotid endarterectomy, early CAS is effective and safe if selectively indicated considering disease severity. Early and delayed CAS provide comparable mRS scores, incidence of symptomatic thromboembolic complications, CHS, and intracranial bleeding.

Abstract T P103: Global Oxygen Extraction Fraction by Blood Sampling to Anticipate Cerebral Hyperperfusion Syndrome Following Carotid Artery Stenting

Background: Cerebral hyperperfusion syndrome (CHS) sometimes occurs after carotid revascularization in patients with severe hemodynamic failure. The incidence of CHS following carotid revascularization is not high. However, once it occurs, it may result in disabled clinical outcome. Therefore, it is very important to anticipate CHS. To anticipate CHS, single-photon emission computed tomography (SPECT) or PET may be useful, but it is impractical for all patients. Purpose: The purpose of our study was to investigate whether or not global oxygen extraction fraction (OEF) by blood sampling anticipated CHS following carotid artery stenting (CAS). Methods: When patients underwent elective CAS from September 2010 to June 2014, we performed blood sampling for OEF calculation before and immediately after elective CAS. Elective CAS was defined as CAS in asymptomatic patients or CAS in patients who experienced a last ischemic attack 30 days or more previously. Data were collected prospectively. OEF was calculated from arteriovenous oxygen difference as follows: OEF = (Ca02-Cv02)/Ca02 where Ca02 is arterial oxygen content and CvO2 is the jugular vein oxygen content. We evaluated baseline features of patients, pre-CAS OEF, post-CAS OEF and the occurrence of CHS. Results: In overall 131 patients, the median pre-CAS OEF was 0.41 (0.37-0.46; IQR), and median post-CAS OEF was 0.42 (0.38-0.47; IQR). Seven patients presented CHS. Between the two groups with and without CHS, there were no differences in patient characteristics. Between the two groups, there were not statistically significant differences of pre-CAS OEF (0.47 vs 0.41). However, patients in CHS group had higher post-CAS OEF than patients in non_CHS group (0.51 vs 0.42) (Mann-Whitney’s U test, p&lt;0.05). Binary logistic regression analysis demonstrated that post-CAS OEF {relative risk; (95%CI); 1.12 (1.01-1.25), p&lt;0.05} was an independent predictor of CHS. The area under the ROC curve for the post-CAS OEF for probable CHS diagnosis was 0.79 and the cut-off value was 50% (sensitivity of 86% and specificity of 88%) for probable CHS. Increase of post-CAS OEF was significantly related to probable CHS. Conclusion: Elevation of blood sampling OEF immediately after CAS anticipated post-CAS CHS.

Hyperperfusion and intracranial haemorrhage after carotid angioplasty with stenting – latest review

The number of endovascular procedures is constantly increasing. As far as the carotid artery is concerned, carotid angio-plasty with stenting (CAS) is an alternative to surgical treatment (carotid endarterectomy; CEA).Two major devastating complications can occur after both procedures – cerebral hyperperfusion syndrome (CHS) and intracranial haemorrhage (ICH).&nbsp;The incidence of CHS and ICH in CAS is fortunately low but overall morbidity and mortality remains high.This latest review re-evaluates the pathogenesis, clinical features, risk factors and diagnostic procedures as well as mana-gement of these two complications.

Intracranial hemorrhage and hyperperfusion syndrome following carotid artery stenting: Risk factors, prevention, and treatment

ObjectivesThe study defined the incidence of cerebral hyperperfusion syndrome and intracranial hemorrhage (ICH) and the risk factors for their development following carotid artery stenting (CAS). BackgroundHyperperfusion syndrome and ICH can complicate carotid revascularization, be it endarterectomy or CAS. Although extensive effort has been devoted to reducing the incidence of ischemic stroke complicating CAS, little is known about the incidence, etiology, and prevention strategies for hyperperfusion and ICH following CAS. MethodsWe retrospectively reviewed the prospective database of 450 consecutive patients who were treated with CAS in our department to identify patients who developed hyperperfusion syndrome and/or ICH. ResultsThe mean age of the patients was 72.7 ± 10.9 years, and the mean diameter narrowing was 84 ± 12.8%. Five (1.1% [95% confidence interval 0.4% to 2.6%]) patients developed hyperperfusion. Three (0.67%) of the five developed ICH. Two of these patients died (0.44%). Symptoms developed within a median of 10 h (range, 6 h to 4 days) following stenting. All five patients had correction of a severe internal carotid stenosis (mean 95.6 ± 3.7%) with a concurrent contralateral stenosis >80% or contralateral occlusion and peri-procedural hypertension. These same risk factors are involved in cerebral hyperperfusion following carotid endarterectomy. The use of platelet glycoprotein IIb/IIIa receptor blockers did not appear to increase the risk ICH. ConclusionsThe hyperperfusion syndrome occurs infrequently following CAS, and ICH occurs in 0.67% of patients. Patients with severe bilateral carotid stenoses may be predisposed to ICH, particularly if there is concurrent arterial hypertension. Patients with these factors may require more intensive hemodynamic monitoring after CAS, including prolongation of hospitalization in some cases.

Cerebral hyperperfusion syndrome after percutaneous transluminal stenting of the craniocervical arteries.

Cerebral hyperperfusion syndrome is a recognized complication of carotid endarterectomy, with a reported incidence of 0.3 to 1.2%. The incidence of cerebral hyperperfusion after endovascular revascularization procedures of the craniocervical arteries remains unknown. We evaluated the incidence of cerebral hyperperfusion syndrome in our endovascular revascularization series. To our knowledge, there are no previous studies evaluating the incidence of hyperperfusion syndrome after percutaneous transluminal angioplasty/stenting. Between March 1996 and February 2000, 140 patients underwent percutaneous transluminal angioplasty/stenting of the craniocervical arteries at our institution. In all patients, selective bilateral arteriography of the carotid and vertebral arteries was performed to document the sites of craniocervical stenosis and collateral blood flow and the results of the endovascular revascularization procedure. We then reviewed all pertinent medical records, arteriographic films, and sectional imaging studies to determine the incidence of cerebral hyperperfusion in this series. Seven patients (5.0%) developed clinical or radiological manifestations of cerebral hyperperfusion. In the target group, percutaneous transluminal stenting achieved a 90 to 100% reduction in stenotic lesions (mean stenosis, 91%) of the carotid (n = 5) and vertebral (n = 2) arteries. All seven patients remained neurologically stable immediately after treatment. There was delayed development of clinical and radiographic findings, suggestive of cerebral hyperperfusion. Six patients showed evidence of ipsilateral hemispheric edema, including two patients who developed intracranial hemorrhage (one parenchymal, one parenchymal and subarachnoid) documented by computed tomographic brain scans. Symptoms resolved within 72 hours in the four patients without hemorrhage. The two patients with hemorrhage recovered during a more protracted period (range, 3 wk to 6 mo). There were no long-term sequelae or deaths during a cumulative follow-up of 84 months (mean follow-up, 12 mo). Hyperperfusion syndrome is an uncommon but potentially serious complication of extracranial and intracranial angioplasty and stenting procedures. The clinical manifestations are similar to hyperperfusion syndrome after carotid endarterectomy; however, the prevalence may be greater in the high-risk cohort commonly referred for endovascular treatment. Our findings suggest that patients undergoing endovascular stenting procedures should be closely monitored for evidence of hyperperfusion, with careful monitoring of blood pressure, heart rate, and anticoagulation. Further research is needed to confirm that cerebral hyperperfusion is the pathogenesis of this condition.