Hemodynamic Compensation via an Excimer Laser-assisted, High-flow Bypass before and after Therapeutic Occlusion of the Internal Carotid Artery

Cerebral revascularization for complex vertebrobasilar artery dissecting aneurysms

Vertebrobasilar artery dissecting aneurysms (VBDAs) are the most surgically challenging type of aneurysm. Cerebral revascularization is the ultimate treatment for complex VBDAs. We retrospectively analysed the characteristics, surgical outcomes and follow-up data of 21 patients who underwent cerebral revascularization to treat complex VBDAs from 2015 to 2022. According to the location of the aneurysm and the anatomic relationship between the VBDA and the PICA, VBDA patients were classified into four groups: aneurysms located at the VA with PICA involvement (10 patients), aneurysms located at the VA without PICA involvement (1 patient), aneurysms located at the basilar apex segment (1 patient) and aneurysms located at the basilar trunk segment (9 patients). A surgical algorithm for complex VBDAs was determined primarily by the location of the aneurysm, the status of the aneurysm and the ability of retrograde blood flow to reach the proximal vertebrobasilar artery. Surgical modalities for patients with aneurysms in the VA with PICA involvement included low-flow (OA-PICA) bypasses with aneurysm trapping, aneurysm excision or reconstructive clip in 8 patients and STA-PCA bypass combined with PICA preservation and aneurysm trapping in 2 patients. In patients with aneurysms in the VA without PICA involvement, aneurysm excision was performed without cerebral bypass. In patients with aneurysms in the basilar apex segment, high-flow bypass (ECA-RA-P2) with aneurysm trapping was performed. In patients with aneurysms in the basilar trunk segment, surgical modalities included high-flow bypasses (ECA-RA-P2 and LVA-RA-P2) with aneurysm trapping or proximal occlusion in 6 patients, ECA-RA-P2 bypass with partial proximal occlusion in 1 patient, ECA-RA-P2 bypass alone in 1 patient, and STA-PCA bypass with R-VA narrowing in 1 patient. Of the 21 patients, 20 experienced clinical improvement or no change, and 17 of 21 patients achieved favourable functional outcomes (mRS ≤ 2). However, one patient died of infarction and respiratory failure postoperatively. Aneurysms were completely obliterated in 13 patients, shrank in 5 patients and stabilized in 2 patients. The median follow-up period was 32.5 months. During the follow-up period, all bypasses were patent, and further clinical improvement was observed in 11 patients. Cerebral revascularization appears to be safe and effective for the treatment of complex VBDAs, and cerebral revascularization could act as a complementary treatment strategy.

Perioperative and long-term complications following therapeutic internal carotid artery occlusion

BACKGROUND

Parent artery occlusion (PAO) is an effective treatment for hemorrhagic diseases associated with the internal carotid artery. There are several reports of long-term cerebral infarction or the formation of de novo cerebral aneurysms following PAO.

MATERIALS AND METHODS

We retrospectively reviewed these complications in 38 patients who underwent PAO for therapeutic treatment. We investigated perioperative cerebral infarctions, long-term cerebral infarctions, and de novo aneurysms.

RESULTS

The mean age of the patients was 64.0 years, and 25 patients (65.8%) were female. The causative diseases were unruptured (n = 19; 50.0%) and ruptured (n = 8; 21.1%) aneurysms. PAO was performed after ischemic tolerance was assessed with balloon test occlusion (BTO), and BTO was performed in 34 patients, of whom 25 (73.5%) had ischemic tolerance. Twenty-six patients (68.4%) were treated with PAO alone, eight (23.5%) with low-flow bypass, and six (17.6%) with high-flow bypass. Perioperative complications occurred in five patients (13.2%): two of the 26 patients (7.7%) who underwent scheduled treatment and three of the 12 patients (25.0%) who underwent emergency treatment. One patient (2.6%) had long-term de novo aneurysm, and none developed cerebral infarction.

CONCLUSIONS

These results showed that the assessment of ischemic tolerance by performing BTO and appropriate revascularization in scheduled treatments are important to reduce perioperative and long-term cerebral infarctions. PAO must be performed with greater caution in emergency treatment.

Vascular responses to abrupt blood flow change after bypass surgery for complex intracranial aneurysms

BACKGROUND

Bypass surgery for complex intracranial aneurysms (IAs) results in drastic blood flow changes in intracranial arteries. The aim of the study was to elucidate how vessels adapt to blood flow changes after bypass surgery with phase-contrast magnetic resonance imaging (PC-MRI).

METHODS

This is a prospective observational study to assess changes of the blood flow in intracranial arteries after bypass surgery for IAs. Flow rates and vessel diameters were measured with PC-MRI in 52 intracranial arteries of 7 healthy volunteers and 31 arteries of 8 IA patients who underwent bypass surgery. Wall shear stress (WSS) was calculated with the Hagen-Poiseuille formula. In 18 arteries of 5 patients, the same measurement was performed 1, 3, and 12 months after surgery.

RESULTS

PC-MRI showed a strong positive correlation between the flow rate and the third power of vessel diameter in both healthy volunteers (r = 0.82, P < 0.0001) and IA patients (r = 0.90, P < 0.0001), indicating the constant WSS. Of the 18 arteries in 5 patients, WSS increased in 7 arteries and decreased in 11 arteries immediately after surgery. In the WSS-increased group, WSS returned to the preoperative value in the third postoperative month. In the WSS-decreased group, WSS increased in the 12th month, but did not return to the preoperative level.

CONCLUSIONS

In a physiological state, WSS was constant in intracranial arteries. Changed WSS after bypass surgery tended to return to the preoperative value, suggesting that vessel diameter and flow rate might be controlled so that WSS remains constant.

Laser application in neurosurgery

BACKGROUND

Technological innovations based on light amplification created by stimulated emission of radiation (LASER) have been used extensively in the field of neurosurgery.

METHODS

We reviewed the medical literature to identify current laser-based technological applications for surgical, diagnostic, and therapeutic uses in neurosurgery.

RESULTS

Surgical applications of laser technology reported in the literature include percutaneous laser ablation of brain tissue, the use of surgical lasers in open and endoscopic cranial surgeries, laser-assisted microanastomosis, and photodynamic therapy for brain tumors. Laser systems are also used for intervertebral disk degeneration treatment, therapeutic applications of laser energy for transcranial laser therapy and nerve regeneration, and novel diagnostic laser-based technologies (e.g., laser scanning endomicroscopy and Raman spectroscopy) that are used for interrogation of pathological tissue.

CONCLUSION

Despite controversy over the use of lasers for treatment, the surgical application of lasers for minimally invasive procedures shows promising results and merits further investigation. Laser-based microscopy imaging devices have been developed and miniaturized to be used intraoperatively for rapid pathological diagnosis. The multitude of ways that lasers are used in neurosurgery and in related neuroclinical situations is a testament to the technological advancements and practicality of laser science.

Current Treatment Strategies for Intracranial Aneurysms: An Overview

Intracranial aneurysm is a leading cause of stroke. Its treatment has evolved over the past 2 decades. This review summarizes the treatment strategies for intracranial aneurysms from 3 different perspectives: open surgery approach, transluminal treatment approach, and new technologies being used or trialed. We introduce most of the available treatment techniques in detail, including contralateral clipping, wrapping and clipping, double catheters assisting coiling and waffle-cone technique, and so on. Data from major trials such as Analysis of Treatment by Endovascular approach of Non-ruptured Aneurysms (ATENA), Internal Subarachnoid Trial (ISAT), Clinical and Anatomical Results in the Treatment of Ruptured Intracranial Aneurysms (CLARITY), and Barrow Ruptured Aneurysm Trial (BRAT) as well as information from other clinical reports and local experience are reviewed to suggest a clinical pathway for treating different types of intracranial aneurysms. It will be a valuable supplement to the current existing guidelines. We hope it could help assisting real-time decision-making in clinical practices and also encourage advancements in managing the disease.

Measurement of Blood Flow in an Intracranial Artery Bypass From the Internal Maxillary Artery by Intraoperative Duplex Sonography

This study explored the hemodynamic characteristics of a subcranial-intracranial bypass from the internal maxillary artery by measuring blood flow on intraoperative duplex sonography. The hemodynamic parameters of the internal maxillary artery (n = 20), radial artery (n = 20), internal maxillary artery-middle cerebral artery bypass (n = 42), and internal maxillary artery-posterior cerebral artery bypass (n = 9) were measured by intraoperative duplex sonography. There was no significant difference in the internal diameters of the internal maxillary and radial arteries (mean ± SD, 2.51 ± 0.34 versus 2.56 ± 0.22 mm; P = .648). The mean radial artery graft length for subcranial-intracranial bypasses was 88.5 ± 12.78 mm (95% confidence interval [CI], 80.8-90.2 mm). Internal maxillary artery-middle cerebral artery bypasses required a shorter radial artery graft than internal maxillary artery-posterior cerebral artery bypasses (77.8 ± 2.47 versus 104.8 ± 4.77 mm; P = .001). The mean flow volumes were 85.3 ± 18.5 mL/min (95% CI, 76.6-93.9 mL/min) for the internal maxillary artery, 72.6 ± 26.4 mL/min (95% CI, 64.3-80.9 mL/min) for internal maxillary artery-middle cerebral artery bypasses, and 45.4 ± 6.7 mL/min (95% CI, 40.7-50.0 mL/min) for internal maxillary artery-posterior cerebral artery bypasses. All grafts were opened after the success of the salvage procedures had been established, and the early patency rates (1 month after the operation) were 95% for internal maxillary artery-middle cerebral artery bypasses and 100% the internal maxillary artery-posterior cerebral artery bypasses. Measurement of blood flow by intraoperative sonography can be helpful in decision making and predicting graft patency and success after neurosurgical bypass procedures.

Internal maxillary artery to intracranial artery bypass: a case series of 31 patients with chronic internal carotid/middle cerebral arterial-sclerotic steno-occlusive disease

OBJECTIVE

To evaluate the effectiveness of internal maxillary artery (IMA) - radial artery graft (RAG) - middle cerebral artery (MCA) bypass surgery for chronic arterial-sclerotic severe stenosis or occlusion of the internal carotid artery (ICA) or MCA.

METHODS

A retrospective study was conducted in 31 patients with ischemic cerebrovascular disease who underwent bypass surgery of the IMA with a RAG of the MCA. Twenty-seven patients had complete occlusion of the ICA or MCA, and four patients had severe stenosis of the M1 segment of the MCA.

RESULTS

Patent IMA-RAG-MCA in 30 (96.8%) patients was confirmed by angiography after surgery. One case developed a new motor aphasia due to unsuccessful bypass. Eleven transient ischemic attacks (TIA) and five ischemic strokes resolved following surgery. The other 14 cases showed some improvement without ischemic events at one month following surgery. Prior to surgery, mean ± SD National Institute of Health Stroke Scale (NIHSS) score was 5.4 ± 1.1 in the ischemic stroke group. In the first month post-procedure, the NIHSS score decreased significantly to 3.8 ± 1.2, (p < 0.01). Perfusion weighted imaging (PWI) or computed tomography perfusion (CTP) indicated improved hemodynamics in 30 patients. In addition, seven patients demonstrated improved glucose metabolism on 18-fluoro-2-deoxy-D-glucose ((18)F-FDG) positron emission tomography (PET) postoperatively. No new neurological deficit occurred in the 30 patients during a 2.19 ± 1.59 years of follow-up.

CONCLUSIONS

By supplying an adequate flow to a larger flow territory of chronically stenotic/occlusive major cerebral arteries, IMA bypass surgery is efficient for restoring hemodynamics in selected patients and improving their neurological deficits.

Selective Arterial Spin Labeling: Techniques and Neurovascular Applications

Knowledge of the distribution of blood flowing from the heart to the brain-feeding arteries is important for the understanding and diagnosis of cerebrovascular diseases. Due to anatomical variations and anomalies within the cerebrovasculature, together with changes caused by various cerebrovascular diseases, there is high variability in the distribution of blood to the parenchyma. This article reviews the various methods that are available for determining the flow territories of the brain-feeding arteries and provides an overview of the different territorial arterial spin labeling (ASL) magnetic resonance imaging (MRI) techniques that have been introduced during the past 2 decades. ASL is a noninvasive method that uses arterial blood as an endogenous contrast agent by magnetically labeling the inflowing blood with radiofrequency pulses. Several selective ASL MRI methods are available to visualize the perfusion territories of individual brain feeding arteries and determine the presence of collateral blood flow pathways. Clinically, these selective perfusion methods may replace more invasive procedures such as catheter angiography for various diseases in which it is of importance to determine the feeding blood vessels, evaluate the presence potential collateral pathways, and monitor the patency of surgical bypasses.

Donor Selection in Flow Replacement Bypass Surgery for Cerebral Aneurysms: Quantitative Analysis of Long-term Native Donor Flow Sufficiency

BACKGROUND:

Graft selection in extracranial-intracranial bypass surgery for cerebral aneurysms has traditionally been based on clinical impression and operator preference. However, decision making can be optimized with a donor selection algorithm based on intraoperative flow data.

OBJECTIVE:

To present long-term follow-up and quantitative assessment of flow sufficiency for native donors selected in this manner.

METHODS:

Patients with bypass for anterior circulation intracranial aneurysms using only a native donor (superficial temporal artery) selected on the basis of an intraoperative flow algorithm over a 10-year period were retrospectively studied. Intracranial hemispheric and bypass flows were assessed preoperatively and postoperatively when available with quantitative magnetic resonance angiography.

RESULTS:

Twenty-two patients with flow data were included (median aneurysm size, 22 mm). The intraoperative flow offer (cut flow) of the superficial temporal artery was sufficient in these cases relative to the flow demand in the sacrificed vessel (59 vs 28 mL/min) to warrant its use. Bypass flow averaged 81 mL/min postoperatively (n = 19). Bypass flows were highest in the immediate postoperative period but remained stable between the intermediate and final follow-up (40 vs 52 mL/min; P = .39; n = 8). Mean ipsilateral hemisphere flows were maintained after bypass (299 vs 335 mL/min; P = .42; n = 7), and remained stable over intermediate and long-term follow-up. Ipsilateral hemispheric flows remained similar to contralateral flows at all time points.

CONCLUSION:

Despite a relative reduction in bypass flow over time, hemispheric flows were maintained, indicating that simple native donors can carry sufficient flow for territory demand long term when an intraoperative flow-based algorithm is used for donor selection.

Training of deep microsurgical skill: Establishment of a high-volume intracranial carotid bypass model

OBJECTIVE

To establish a model for a high-volume intracranial carotid bypass operation.

METHODS

High-volume internal carotid-middle cerebral artery bypass was performed on 9 cadaver heads with arteries of porcine forearms as grafts by 6 residents with no previous experience in vascular anastomosis on cadavers. The intima was dissected immediately after the anastomoses were completed to observe the patency of anastomosis.

RESULTS

After different duration periods of training using this model, 36 vascular anastomoses on 18 sides were successfully performed by the 6 residents with a self-made difficulty regulation device. As the difficulty level increased, the time needed for anastomosis lengthened and patency rate showed a decreasing trend. As the amount of training increased, the residents were able to decrease the amount of time to complete the operation with increasing patency rates.

CONCLUSIONS

The model of high-volume internal carotid-middle cerebral artery bypass with arteries of porcine forearms has the advantages of material similarity, easy access of grafts, better simulation of intraoperative conditions, and adjustable difficulties. Our results suggest that this new procedure has a better simulation-training platform which is closer to the real surgical procedure for surgeons willing to master the technique of a high-volume bypass operation.

Cerebral Blood Flow after Acute Bypass with Parent Artery Trapping in Patients with Ruptured Supraclinoid Internal Carotid Artery Aneurysms

BACKGROUND

Bypass with parent artery trapping is an alternative treatment method for ruptured internal carotid artery (ICA) aneurysms when clipping or coiling is contraindicated. However, the efficacy and safety of this strategy during the acute stage of subarachnoid hemorrhage (SAH) is undetermined.

METHODS

A retrospective review of 955 consecutive patients presenting SAH between 2006 and 2014 identified 17 patients with ruptured ICA aneurysms treated by bypass with parent artery trapping within 72 hours after the bleeding (bypass group). The 26 cases with ruptured posterior communicating artery aneurysms treated with clipping during the same period were defined as a control group (clipping group). Postoperative cerebral blood flow (CBF) was evaluated by single photon emission computed tomography (SPECT). We analyzed the postoperative hemodynamic status, surgical complications, and the clinical outcomes.

RESULTS

Postoperative rebleeding did not occur in any of the cases. CBF in the first postoperative week in the bypass group was lower than that in the clipping group (P = .0165). This CBF decrease improved in the second postoperative week and did not differ from that of the clipping group. The incidence of acute ischemic complications was significantly higher in the bypass group (P = .0284), but the incidence of delayed cerebral ischemia did not differ between the 2 groups. The incidence of favorable outcomes at 6 months was 82.4% in the bypass group and 81% in the clipping group.

CONCLUSIONS

Although the transient CBF decrease with acute ischemic complications should be noted, acute bypass with parent artery trapping is safe and effective for unclippable/uncoilable ruptured ICA aneurysms.

Effect of age and vascular anatomy on blood flow in major cerebral vessels

Measurement of volume flow rates in major cerebral vessels can be used to evaluate the hemodynamic effects of cerebrovascular disease. However, both age and vascular anatomy can affect flow rates independent of disease. We prospectively evaluated 325 healthy adult volunteers using phase contrast quantitative magnetic resonance angiography to characterize these effects on cerebral vessel flow rates and establish clinically useful normative reference values. Flows were measured in the major intracranial and extracranial vessels. The cohort ranged from 18 to 84 years old, with 157 (48%) females. All individual vessel flows and total cerebral blood flow (TCBF) declined with age, at 2.6 mL/minute per year for TCBF. Basilar artery (BA) flow was significantly decreased in individuals with one or both fetal posterior cerebral arteries (PCAs). Internal carotid artery flows were significantly higher with a fetal PCA and decreased with a hypoplastic anterior cerebral artery. Indexing vessel flows to TCBF neutralized the age effect, but anatomic variations continued to impact indexed flow in the BA and internal carotid artery. Variability in normative flow ranges were reduced in distal vessels and by examining regional flows. Cerebral vessel flows are affected by age and cerebrovascular anatomy, which has important implications for interpretation of flows in the disease state.

Impact of cervical internal carotid clamping and radial artery graft bypass on cortical arterial perfusion pressure during craniotomy

Strategic cervical internal carotid occlusion is employed either temporarily or permanently in various neurosurgical procedures. The aim of the present study was to assess changes in cortical arterial pressure during cervical internal carotid cross-clamping before and after the placement of radial artery (RA) graft bypass in the treatment of complex carotid artery aneurysms. Perfusion pressure of the middle cerebral artery (MCA) was assessed in 22 patients with complex carotid aneurysm treated with RA graft bypass. Regional cerebral blood flow was assessed postoperatively using single-photon computed tomography. Mean cortical blood pressure (mcBP) was found to be 48.2 ± 24.2 and 97.0 ± 24.0 % of baseline after clamping the cervical internal carotid artery and opening the RA graft bypass, respectively. Cerebral perfusion pressure estimated by the mcBP failed to sustain a critical limit of greater than 70 mmHg under craniotomy in 16 out of 20 (80 %) patients. There was an inverse correlation in mcBP between the baseline and after the placement of the RA graft bypass (r = 0.66, P < 0.005). Postoperative regional cerebral blood flow in the MCA territory on the ipsilateral side of the aneurysm was 97 ± 7 % of that of the contralateral side after internal carotid artery (ICA) ligation combined with RA graft bypass. Substantial pressure reductions in cerebral cortical arteries were observed during the cervical internal carotid cross-clamping. Perfusion pressure in peripheral cortical arteries after the placement of the RA graft bypass was comparable to the state before ICA clamping.

Detection of intracranial in-stent restenosis using quantitative magnetic resonance angiography

BACKGROUND AND PURPOSE

In-stent restenosis (ISR) after angioplasty/stenting for intracranial stenosis has been reported in up to 25% to 30% of patients. Detection and monitoring of ISR relies primarily on serial catheter angiography, because noninvasive imaging methods are typically hampered by stent-related artifact. We examined the value of serial vessel flow measurements using quantitative magnetic resonance angiography (QMRA) in detection of ISR.

MATERIAL AND METHODS

Records of patients undergoing stenting for intracranial symptomatic stenosis >50% between 2005 and 2009 were retrospectively reviewed. Angiographic images were graded by a blinded neurointerventionalist for stenosis pretreatment, immediately after treatment, and during follow-up. Flow in the affected vessel measured by QMRA was recorded; > 25% reduction in flow was considered indicative of an adverse change. Clinical data regarding neurological outcome were also collected.

RESULTS

Twenty-eight patients underwent stenting during the time interval studied. Of these, 12 patients (mean age, 55.5 years; 8 female) had contemporaneous angiography and QMRA and were analyzed. Median follow-up was 9 months. Six patients (50%) demonstrated angiographic restenosis 2 to 12 months after treatment; all had an analogous decrease in flow in the vessel of interest. Of 3 patients with more severe flow decrement (> 50%), 2 experienced stroke. None of the patients without angiographic ISR demonstrated a flow decrease on QMRA.

CONCLUSIONS

In this preliminary series, flow decrease on QMRA is highly predictive of angiographic ISR. Additionally, the degree of flow decrement correlates with symptomatic ISR. QMRA may provide a useful noninvasive tool for serial monitoring after intracranial stenting.

Associations between total cerebral blood flow and age related changes of the brain

Background and Purpose

Although total cerebral blood flow (tCBF) is known to be related to age, less is known regarding the associations between tCBF and the morphologic changes of the brain accompanying cerebral aging. The purpose of this study was to investigate whether total cerebral blood flow (tCBF) is related to white matter hyperintensity (WMH) volume and/or cerebral atrophy. Furthermore, we investigate whether tCBF should be expressed in mL/min, as was done in all previous MR studies, or in mL/100 mL/min, which yielded good results in precious SPECT, PET and perfusion MRI studies investigating regional cerebral blood flow.

Materials and Methods

Patients were included from the nested MRI sub-study of the PROSPER study. Dual fast spin echo and FLAIR images were obtained in all patients. In addition, single slice phase contrast MR angiography was used for flow measurements in the internal carotids and vertebral arteries. tCBF was expressed in both mL/min and mL/100 mL/min.

Results

We found a significant correlation between tCBF in mL/min and both age (r = −.124; p = p≤.001) and parenchymal volume (r = 0.430; p≤.001). We found no association between tCBF in mL/min and %-atrophy (r = −.077; p = .103) or total WMH volume (r = −.069; p = .148). When tCBF was expressed in mL/100 mL/min the correlation between tCBF and age was no longer found (r = −.001; p = .985). Multivariate regression analyses corrected for age showed a significant correlation between tCBF in mL/100 mL/min and WMH volume (r = −.106; p = .044). No significant association between tCBF in mL/100 mL/min and %-atrophy was found.

Conclusion

From this study we conclude that, when evaluating tCBF alterations due to various pathologies, tCBF should in mL/100 mL/min instead of mL/min. Furthermore, changes or differences in WMH volume should be accounted for.

OCCIPITAL ARTERY-TO-POSTERIOR INFERIOR CEREBELLAR ARTERY BYPASS FOR TREATMENT OF BILATERAL VERTEBRAL ARTERY OCCLUSION: THE ROLE OF QUANTITATIVE MAGNETIC RESONANCE ANGIOGRAPHY NONINVASIVE OPTIMAL VESSEL ANALYSIS

OBJECTIVE

Patients with partial or complete bilateral vertebral artery occlusion often present with signs and symptoms of transient ischemic attacks or infarction. Advances in phase contrast magnetic resonance imaging have led to noninvasive assessment of volumetric blood flow rates and direction that help in the workup and management of these patients.

CLINICAL PRESENTATION

We present the case of a patient with symptoms of vertebrobasilar insufficiency without previous transient ischemic attacks or stroke. Quantitative magnetic resonance angiography (QMRA) demonstrated bilateral vertebral artery occlusion with reversal of flow in the basilar and vertebral arteries to the level of the posterior inferior cerebellar arteries bilaterally. A prominent right posterior communicating artery filled the basilar artery and proximal vertebral arteries.

INTERVENTION

The presence of reversal and diminished flow in the basilar and vertebral arteries suggested that occipital artery-to-posterior inferior cerebellar artery bypass would improve posterior circulation, relieve symptoms, and reduce the risk of infarction. Postoperative QMRA and angiography confirmed revascularization, and QMRA confirmed correction of blood flow direction.

CONCLUSION

This case illustrates the potential of QMRA as part of a comprehensive cerebrovascular assessment, operative planning, and follow-up of patients with vertebrobasilar insufficiency.

Blood blister-like aneurysms of the internal carotid artery trunk causing subarachnoid hemorrhage: treatment and outcome

OBJECT

The object of this study was to evaluate cases of subarachnoid hemorrhage (SAH) from ruptured blood blister-like aneurysms (BBAs) of the internal carotid artery (ICA) trunk.

METHODS

The authors performed a single-center, retrospective study. Data analyzed were patient age, sex, Hunt and Hess grade, Fisher grade, time from SAH to hospitalization, aneurysm size and location, collateral capacity of the circle of Willis, time from hospitalization to aneurysm repair, type of aneurysm repair, complications, and Glasgow Outcome Scale (GOS) score at follow-up.

RESULTS

A total of 211 patients suffered SAH from ICA aneurysms. Of these, 14 patients (6.6%) had ICA trunk BBAs; 6 men and 8 women. The median age was 47.8 years (range 29.9-67.7 years). The Hunt and Hess grade was IV or V in 7 cases, and SAH was Fisher Grade 3 + 4 in 6. All aneurysms were small (< 1 cm), without relation to vessel bifurcations, and usually located anteromedially on the ICA trunk. Three patients were treated with coil placement and 11 with clip placement. Of the 7 patients in whom the ICA was preserved, only 1 had poor outcome (GOS Score 2). In contrast, cerebral infarcts developed in all patients treated with ICA sacrifice, directly postoperatively in 2 and after delay in 5. Six patients died, 1 survived in poor condition (GOS Score 3; p < 0.001).

CONCLUSIONS

Internal carotid BBAs are rare, small, and difficult to treat endovascularly, with only 2 of 14 patients successfully treated with coil placement. The BBAs rupture easily during surgery (ruptured in 6 of 11 surgical cases). Intraoperative aneurysm rupture invariably led to ICA trap ligation. Sacrifice of the ICA within 48 hours of an SAH led to very poor outcome, even in patients with adequate collateral capacity on preoperative angiograms, probably because of vasospasm-induced compromise of the cerebral collaterals.

Sutureless nonocclusive bypass surgery in combination with an expanded polytetrafluoroethylene graft. Laboratory investigation

OBJECT

Cerebral aneurysms that cannot be treated by clip or coil placement can be treated with high-flow bypass surgery using techniques such as the excimer laser-assisted nonocclusive anastomosis (ELANA). To simplify the technique, a sutureless ELANA (SELANA) was developed in combination with an expanded polytetrafluoroethylene (ePTFE) graft.

METHODS

In 18 rabbits a bypass was constructed on the abdominal aorta using the SELANA technique with an ePTFE graft, resulting in 18 bypasses and 36 anastomoses. Short-term effects were analyzed in the first 2 weeks and at 2 and 3 months after the procedure. Patency was evaluated using quantitative ultrasound flowmetry. The anastomotic sites were studied using scanning electron microscopy.

RESULTS

Construction of the bypass using the SELANA technique was easier and faster (15-25 minutes) compared with bypasses made with the ELANA technique (> 90 minutes). At the end of follow-up, 16 of 18 bypasses were patent. Of 36 SELANA anastomoses, 32 could be completed without short temporary occlusion of the recipient vessel. Scanning electron microscopy showed complete coverage of all anastomoses with neointimal repair tissue after 10 days.

CONCLUSIONS

The SELANA technique provides further advantages over the conventional ELANA technique in ease of use and shortening of procedure time. The patency rate in this series was 89% and neointima repair tissue at the anastomosis site was complete after 10 days. Further experimental studies of the long-term patency and safety of this technique are necessary before clinical application.

Emergency extra-intracranial bypass surgery in the treatment of cerebral aneurysms

The need of an emergency bypass in hazardous situations during treatment of intracranial aneurysms has rarely been addressed in the literature. We report our 10 year experience with emergency bypass for aneurysm treatment. We retrospectively analyzed the data of patients who underwent emergency bypass surgery for the treatment of an intracranial aneurysm and compared the results with patients treated with bypass as a planned procedure during the same time period. Three groups were formed: group I, emergency bypass during clipping procedure; group II, emergency bypass for therapy refractory vasospasm; group III, planned bypass surgery. Sixteen patients (35%) out of 46 were treated with emergency bypass. In group I (11 patients) mortality was 37% and a good outcome (GOS 4 & 5) was achieved in 36%. In group II (5 patients) mortality was 20% and good outcome was reached in 60%. In group III (30 patients) mortality was 10% and good outcome was achieved in 86.6%. Outcome was worse in patients with additional SAH. An emergency bypass procedure as part of the aneurysm treatment should be considered in risky situations. Accurate timely decision-making is crucial combined with a fast and secure bypass technique. Treatment of refractory vasospasm with emergency bypasses may help to improve outcome in selected patients.

Evaluation of extracranial-intracranial bypass using quantitative magnetic resonance angiography

OBJECT

To date, angiography has been the primary modality for assessing graft patency following extracranial-intracranial bypass. The utility of a noninvasive and quantitative method of assessing bypass function postoperatively was evaluated using quantitative magnetic resonance (MR) angiography.

METHODS

One hundred one cases of bypass surgery performed over a 5.5-year period at a single institution were reviewed. In 62 cases, both angiographic and quantitative MR angiographic data were available. Intraoperative flow measurements were available in 13 cases in which quantitative MR angiography was performed during the early postoperative period (within 48 hours after surgery). There was excellent correlation between quantitative MR angiographic flow and angiographic findings over the mean 10 months of imaging follow up. Occluded bypasses were consistently absent on quantitative MR angiograms (four cases). The flow rates were significantly lower in those bypasses that became stenotic or reduced in diameter as demonstrated by follow-up angiography (nine cases) than in those bypasses that remained fully patent (mean +/- standard error of the mean, 37 +/- 13 ml/minute compared with 105 +/- 7 ml/minute, p = 0.001). Flows were appreciably lower in poorly functioning bypasses for both vein and in situ arterial grafts. All angiographically poor bypasses (nine cases) were identifiable by absolute flows of less than 20 ml/minute or a reduction in flow greater than 30% within 3 months. Good correlation was seen between intraoperative flow measurements and early postoperative quantitative MR angiographic flow measurements (13 cases, Pearson correlation coefficient = 0.70, p = 0.02).

CONCLUSIONS

Bypass grafts can be assessed in a noninvasive fashion by using quantitative MR angiography. This imaging modality provides not only information regarding patency as shown by conventional angiography, but also a quantitative assessment of bypass function. In this study, a low or rapidly decreasing flow was indicative of a shrunken or stenotic graft. Quantitative MR angiography may provide an alternative to standard angiography for serial follow up of bypass grafts.

Extracranial-intracranial bypass for the treatment of cavernous sinus aneurysms

The optimal management of symptomatic cavernous sinus aneurysms remains controversial. Carotid occlusion is a simple procedure, but carries an ongoing risk of early and late stroke. Cerebral revascularisation is technically demanding and carries a risk of morbidity and mortality of around 10%. Eight patients treated with an extracranial-intracranial vascular bypass graft over a period of 44 months for symptomatic cavernous sinus aneurysms are reviewed. At a mean follow-up of 20 months, seven patients (87.5%) had an excellent outcome (Glasgow Outcome Score 5) while one patient suffered a perioperative stroke. In only one case, where the radial artery had been used, the graft became occluded. The results of this series seem to indicate that cerebral revascularisation is an effective treatment for patients with symptomatic cavernous sinus aneurysms.

Hemodynamic effect of carotid stenting and carotid endarterectomy

BACKGROUND

Carotid angioplasty with stent placement (CAS) may offer an alternative treatment to carotid endarterectomy (CEA). However, in contrast to CEA, which has been shown to normalize impaired cerebral hemodynamics, the effects of CAS remain unclear. To investigate alterations in cerebral hemodynamics, we prospectively studied patients undergoing CAS and compared them with a group of similar patients undergoing CEA.

METHODS

Twenty-three patients undergoing CAS for recently symptomatic internal carotid artery (ICA) stenosis were prospectively studied. Volume flow in the ICAs and basilar artery (BA) were measured with magnetic resonance volume flow quantification before CAS and 1 month after. The results were compared with those in 13 similar patients undergoing CEA and 40 control subjects without ICA stenosis.

RESULTS

After CAS, volume flow in the ipsilateral ICA increased from 114 +/- 17 to 231 +/- 17 mL/min (P < .001), and total volume flow (ICAs plus BA) increased from 495 +/- 24 to 552 +/- 28 mL/min (P < .05). No significant changes were seen in the contralateral ICA and BA after CAS. Total volume flow and flow in the stenosed ICA normalized after CAS compared with control subjects. Volume flow values similarly improved after CEA.

CONCLUSIONS

CAS results in a normalization of impaired cerebral hemodynamics, as assessed by magnetic resonance volume flow measurements. The degree of improvement is similar to that seen after CEA.

Combined use of a radial fore arm free flap for extra-intracranial bypass and for antero-lateral skull base reconstruction--a new technique and review of literature

This article describes a new surgical technique consisting of the combined use of a fascial radial fore arm free flap (RFFF) as vascular graft for extra-intracranial bypass and as dura mater plasty for reconstruction of the antero-lateral skull base. This new technique is illustrated by a case of a complex intracranial meningioma with extracranial extension necessitating resection of internal carotid artery. The technical issues of antero-lateral skull base reconstruction and extra-intracranial bypass are discussed and the literature is reviewed.

Recanalization of long-lasting middle cerebral artery occlusion by a combination of surgical and interventional approaches: technical case report

OBJECTIVE AND IMPORTANCE

In strictly selected cases of middle cerebral artery (MCA) occlusion, revascularization by extracranial-intracranial (EC-IC) bypass can be considered. The interventional recanalization of the occlusion under direct surgical control has not been reported in the literature so far.

CLINICAL PRESENTATION

A 39-year-old Caucasian female patient had experienced an ischemic stroke 15 years before she came to our attention. At that time, occlusion of the right MCA was diagnosed by angiography. Her neurological deficit resolved within 6 months. Fifteen years later, the patient experienced repeated numbness of her left-sided extremities, which was refractory to medical treatment. Angiography revealed an occluded M1 segment of the MCA. Perfusion computed tomography without and after CO2 stimulation disclosed impaired cerebrovascular capacity.

INTERVENTION

The patient was scheduled for EC-IC bypass. The MCA tree was exposed, and the occluded portion was found to be 10 mm long. We then decided to reopen the vessel by balloon dilation under direct visual control. A catheter was advanced to the M1 origin, where a glidewire was passed into the vessel lumen. With only a little help from the surgeon, it was surprisingly easy to direct the glidewire through the occluded segment. At this time, flow through the M1 segment was re-established. Flow through the MCA that had occluded for 15 years was re-established.

CONCLUSION

On the basis of our experience, in nonatherosclerotic occlusions, intravascular intervention may be considered.

ELANA: Excimer Laser-Assisted Nonocclusive Anastomosis for extracranial-to-intracranial and intracranial-to-intracranial bypass: a review

ELANA, excimer laser-assisted nonocclusive anastomosis, is a technique using an excimer laser/catheter system for intracranial bypass surgery of the brain. The technique has been developed over the past 12 years by Tulleken and colleagues at UMC Utrecht in The Netherlands for treatment of primarily untreatable giant aneurysms. We review here the emergence of transplanted conduit bypass as a valuable technique for managing these lesions and the subsequent development of ELANA bypass. The ELANA technique allows the operating surgeon to perform an extracranial-to-intracranial or intracranial-to-intracranial bypass using a transplanted large caliber conduit without occlusion of the recipient artery, thus eliminating intraoperative ischemic insult related to temporary occlusion time. We describe the ELANA technique, illustrate it with intraoperative photos, and review the relevant literature. ELANA is shown to be safe; we discuss its advantages over conventional techniques.

Altered Flow Territories after Extracranial-Intracranial Bypass Surgery

OBJECTIVE:

To prevent stroke after carotid sacrifice and to augment cerebral perfusion in patients with internal carotid artery (ICA) occlusion, high-flow extracranial-intracranial (EC-IC) bypass operations are performed. Although the function and efficacy of the bypass is monitored during surgery, the postoperative flow through the bypass is significantly lower than the flow in the contralateral ICA. Thus far, it is unknown whether decreased bypass flow is caused by a low tissue perfusion or by a relatively small flow territory.

METHODS:

Seven patients, four with an atherosclerotic ICA occlusion and three with a giant aneurysm of the ICA, were investigated; each underwent a high-flow EC-IC bypass and permanent occlusion of the ICA. Cerebral blood flow was measured with arterial spin labeling perfusion magnetic resonance imaging. Separate flow territory mapping of the EC-IC bypass, contralateral ICA, and posterior circulation was performed with selective arterial spin labeling magnetic resonance imaging.

RESULTS:

No significant difference was found in cerebral blood flow between the hemisphere ipsilateral to the EC-IC bypass (70.9 ± 11.3 ml/min/100 g tissue), contralateral to the EC-IC bypass (71.9 ± 14.3 ml/min/100 g tissue), and comparable findings in 50 healthy control participants (69.1 ± 17.5 ml/min/100 g tissue). Paired analysis of the individual flow territories demonstrated a 15% volume reduction (P = 0.018) in flow territory of the EC-IC bypass compared with the contralateral side.

CONCLUSION:

In the present study, we demonstrate the feasibility of selective arterial spin labeling magnetic resonance imaging for clinical follow-up of patients after high-flow EC/IC bypass surgery, providing both information on flow territories and the level of regional cerebral blood flow.

Long-term reendothelialization of excimer laser—assisted nonocclusive anastomoses compared with conventionally sutured anastomoses in pigs

Object. In contrast to conventional anastomosis methods, the excimer laser—assisted nonocclusive anastomosis (ELANA) technique involves a platinum ring and intima—adventitia apposition with a rim of medial and adventitial layers exposed to the bloodstream. The authors assessed the reendothelialization of porcine carotid arteries through ELANA compared with conventional anastomosis by using scanning electron microscopy.

Methods. In 28 pigs a bypass with one ELANA and one conventional anastomosis was made on the left common carotid artery. All patent anastomoses were evaluated intraoperatively with the aid of an ultrasonographic flowmeter and postoperatively by using scanning electron microscopy at 2 weeks, 2 months, 3 months, and 6 months thereafter. Twenty-four of 28 bypasses (48 of 56 end-to-side anastomoses) were fully patent at the time of evaluation. On scanning electron microscopic evaluation of the bypasses, all 48 patent anastomoses showed complete reendothelialization, including all 24 ELANAs in which the endothelium covered the rim and the laser-ablated edge completely. No endothelial difference was observed between conventional anastomoses and ELANAs, aside from the obvious anatomical differences like the platinum ring, which had been completely covered with endothelium. At 6 months postsurgery, remodeling of the ELANA was observed, leaving the ring covered with a layer of endothelium as the most narrow part of the anastomosis.

Conclusions. In long-term experiments, ELANA allows reendothelialization comparable to that achieved with conventional anastomosis. Considering its nonocclusive and high-flow characteristics, the ELANA technique is preferable in cerebral revascularization procedures.

A Novel Minimally Occlusive Microvascular Anastomosis Technique Using a Temporary Intraluminal Shunt: A Prospective Technique to Minimize Brain Ischemia Time during Superficial Temporal Artery-to-Middle Cerebral Artery Bypass

OBJECTIVE:

To describe a new technique of suturing microvessels with persistent perfusion via a temporary intraluminal microshunt.

METHODS:

Experiments were conducted in Wistar rats. Abdominal aorta grafts were explanted from donor rats. A soft silicon microcatheter was introduced into the lumen of this graft. The abdominal aorta of a recipient rat was prepared for end-to-side microvascular anastomosis. Acland clamps (S&T AG, Neuhausen, Switzerland) were applied, and a linear arteriotomy was made. One end of the graft-clad microcatheter was introduced into the lumen and occluded with a fenestrated Acland clamp. At a more distal part, a similar arteriotomy was performed, and the other end of the microcatheter was introduced into the lumen and clamped with a fenestrated Acland clip. This created a temporary shunt through the graft-clad microcatheter. Then, the graft was anastomosed to the arteriotomies at both ends, over the microcatheter, in an end-to-side manner. The microcatheter was explanted from the vessel lumen through an arteriotomy in the middle of the graft. The graft was clipped short to close this arteriotomy. The mean total occlusion time before perfusion was reestablished amounted to 3.7 minutes. This experiment was repeated in 12 animals (6 with and 6 without heparin) without technical complications. As controls, conventional anastomoses were made in 2 animals.

RESULTS:

Suturing microvessels mandates their occlusion during the period of anastomosis. Although ischemia is well tolerated by other tissue types, the brain is quite sensitive to even short windows of ischemia. Nonocclusive anastomotic techniques have been developed recently. These are confined to vessels with luminal diameters greater than 3 mm. We have evolved a novel technique that can be used with microvessels, as pertinent to superficial temporal artery-to-middle cerebral artery bypass.

CONCLUSION:

We have described a new technique for performing microvascular anastomoses over a temporary intraluminal microcatheter shunt.

Distribution of Cerebral Blood Flow in the Circle of Willis

PURPOSE

To prospectively determine the effect of anatomic variations in the circle of Willis on volume flow in the internal carotid arteries (ICAs) and basilar artery (BA).

MATERIALS AND METHODS

Institutional review board approval and informed consent were obtained. Phase-contrast magnetic resonance (MR) angiography was used to measure the volume flow in the BA and ICAs in 208 patients (182 men, 26 women; mean age, 60 years) with symptomatic atherosclerosis or risk factors for atherosclerosis. Patients with steno-occlusive disease were excluded, and flow values were normalized for age. Three-dimensional time-of-flight MR angiograms were used to assess the anatomy of the circle of Willis. Differences in volume flow between a complete circle of Willis, a circle with a missing A1 segment, and a circle with a fetal-type posterior cerebral artery were analyzed (analysis of variance and Scheffe post hoc tests).

RESULTS

The ICA volume flow in subjects with a complete configuration of the circle of Willis was 245 mL/min +/- 65 (standard deviation). Flow in the contralateral ICA was significantly increased (P < .01) in subjects with a missing A1 segment (303 mL/min +/- 56) compared with control subjects and compared with flow on the ipsilateral side (214 mL/min +/- 94; P < .01). In subjects with a unilateral or bilateral fetal-type posterior cerebral artery, the ICA volume flow was increased (P < .01) and the BA volume flow was decreased (P < .01) in comparison with the flow in subjects with no fetal-type circle of Willis.

CONCLUSION

Large asymmetries in volume flow between the right and left ICAs or decreased volume flow in the BA is not necessarily caused by vascular disease but may be caused by variations in the anatomy of the circle of Willis.

Phase-contrast magnetic resonance imaging measurements of cerebral autoregulation with a breath-hold challenge: a feasibility study

BACKGROUND AND PURPOSE

Vasomotor reactivity (VMR) testing can identify patients with hemodynamically critical cerebrovascular disease. The use of VMR has been limited by the invasiveness of most of the available methods and of acetazolamide as VMR stimulus. In the present study, we evaluated a completely noninvasive VMR approach by combining quantitative phase-contrast magnetic resonance imaging (MRI) with a breath-hold challenge.

METHODS

Volume flow rates in the right and left internal carotid artery (ICA), basilar artery (BA), superior sagittal sinus, and sinus rectus were measured on 2-dimensional phase-contrast MR angiograms (MRAs) with a temporal resolution of 4.3 seconds. In 20 healthy control subjects, the VMR was assessed during 2 consecutive 30-second periods of breath-holding.

RESULTS

A flow increase on breath-holding of 66% was found for the left ICA (240+/-54 mL/min to 398+/-120 mL/min; P<0.01), 59% for the right ICA (253+/-98 mL/min to 402+/-159 mL/min; P<0.01), 71% for the BA (107+/-48 mL/min to 184+/-79 mL/min; P<0.01), 62% for the superior sagittal sinus (232+/-75 mL/min to 375+/-130 mL/min; P<0.01), and 65% for the sinus rectus (77+/-30 mL/min to 127+/-38 mL/min; P<0.01). The coefficient of variation for the total volume flow increase in the brain feeding arteries (ICAs and BA) between the first and the second breath-holds was 18%.

CONCLUSIONS

The combination of MRA phase-contrast volume flow measurements and a breath-holding challenge allows for a fast, completely noninvasive, and reproducible assessment of VMR.