Role of intraoperative microvascular Doppler in the microsurgical management of intracranial aneurysms

The Use of Intraoperative Microvascular Doppler in Vascular Neurosurgery: Rationale and Results-A Systematic Review

Surgical treatment of neurovascular lesions like intracranial aneurysms, arteriovenous malformations and arteriovenous dural fistulas is still associated with high morbidity. Several recent studies are providing increasing insights into reliable tools to improve surgery and reduce complications. Inadvertent vessel compromise and incomplete occlusion of the lesion represent the most possible complications in neurovascular surgery. It is clear that direct visual examination alone does not allow to identify all instances of vessel compromise. Various modalities, including angiography, microvascular Doppler and neurophysiological studies, have been utilized for hemodynamics of flow vessels in proper clipping of the aneurysm or complete obliteration of the lesion. We intended to review the current knowledge about the intraoperative microvascular Doppler (iMDS) employment in the most updated literature, and explore the most recent implications not only in intracranial aneurysms but also in neurovascular lesions like arteriovenous malformations (AVMs) and arteriovenous dural fistulas (AVDFs). According to the PRISMA guidelines, systematic research in the most updated platform was performed in order to provide a complete overview about iMDS employment in neurovascular surgery. Twelve articles were included in the present paper and analyzed according to specific research areas. iMDS employment could represent a crucial tool to improve surgery in neurovascular lesions. The safety and effectiveness of the surgical treatment of neurovascular lesions like intracranial aneurysm and other neurovascular lesions like AVMs and AVDFs requires careful and accurate consideration regarding the assessment of anatomy and blood flow. Prognosis may depend on suboptimal or incomplete exclusion of the lesion.

Application of intraarterial superselective indocyanine green angiography in bypass surgery for adult moyamoya disease

Background

Extracranial-intracranial (EC-IC) bypass surgery is the main treatment approach to moyamoya disease, and an accurate assessment of the patency of anastomosis is critical for successful surgery. So far, the most common way to do this is the intraoperative intravenous indocyanine green (ICG) video-angiography. Intra-arterial ICG-VA has been applied to treat peripheral cerebral aneurysms, spinal arteriovenous fistulas, and dural arteriovenous fistulas, but few reports have concerned the use of arterial injection of ICG to evaluate anastomotic patency. This research aims to explore the feasibility and effects of catheter-guided superficial temporal artery injection of ICG in the evaluation of anastomotic patency after bypass surgery.

Methods

In this study, 20 patients with moyamoya disease or syndrome who underwent bypass surgery were divided into two groups, one who received intravenous ICG angiography and the other who received intra-arterial ICG angiography, to compare the two injection methods for vascular anastomosis patency. We conducted conventional intraoperative digital subtraction angiography (DSA) in a hybrid operating room during extracranial-intracranial (EC-IC) bypass surgery, including the additional step of injecting ICG into the main trunk of the superficial temporal artery (STA) through a catheter.

Results

Intra-arterial injection of indocyanine green video-angiography (ICG-VA) indicated good patency of the vascular anastomosis when compared with conventional digital subtraction angiography (DSA) and intravenous ICG-VA, confirming the feasibility of using the arterial injection of ICG for assessing anastomotic patency. And intra-arterial ICG-VA results in faster visualization than intravenous ICG-VA (p < 0.05). Besides, ICG-VA through arterial injection provided valuable information on the vascular blood flow direction after the bypass surgery, and allowed for visual inspection of the range of cortical brain supply from the superficial temporal artery and venous return from the cortex. Moreover, arterial injection of ICG offered a rapid dye washout effect, reducing the repeat imaging time.

Conclusion

This study indicates that intra-arterial ICG-VA has good effects in observing the direction of blood flow in blood vessels and the range of cortical brain supply from the STA, which reflects blood flow near the anastomosis and provides additional information that may allow the postoperative prediction of cerebral hyperperfusion syndrome. However, the procedure of intra-arterial ICG-VA is relatively complicated compared to intravenous ICG-VA.

Application of intraoperative infrared thermography in bypass surgery for adult moyamoya syndrome: A preliminary study

Background and objectives

Cerebral revascularization surgery is the mainstay of treatment for moyamoya syndrome (MMS) today, and intraoperative determination of the patency of the revascularized vessel is a critical factor in the success of the procedure. Currently, major imaging modalities include intraoperative indocyanine green (ICG) videoangiography (ICG-VA), digital subtraction angiography (DSA), and vascular ultrasound Doppler. Infrared thermography is a modern imaging modality with non-contact devices for the acquisition and analysis of thermal data. We aimed to investigate the feasibility and advantages of infrared thermography in determining anastomotic patency during MMS surgery.

Methods

Indocyanine green videoangiography and infrared thermography were performed simultaneously in 21 patients with MMS who underwent bypass surgery. The detection result of vessel patency was compared, and the feasibility and advantages of infrared thermography were assessed.

Results

The patency of the anastomosis was accurately determined in 21 patients using either ICG angiography or infrared thermography. In 20 patients, the results of infrared thermography showed that the vascular anastomosis was unobstructed, and there was an agreement with the subsequent results of ICG-VA. In one patient, we suspected inadequate patency after testing the anastomosis with infrared thermography, and the results of ICG-VA evaluation of the anastomosis confirmed that there was indeed an anastomotic obstruction.

Conclusion

Compared with ICG-VA, infrared thermography might offer an alternative non-invasive, contrast-free option in assessing anastomosis patency compared with ICG-VA, and it is likely to become more widely used in the clinic in the near future.

ASNM and ASN joint guidelines for transcranial Doppler ultrasonic monitoring: An update

Today, it seems prudent to reconsider how ultrasound technology can be used for providing intraoperative neurophysiologic monitoring that will result in better patient outcomes and decreased length and cost of hospitalization. An extensive and rapidly growing literature suggests that the essential hemodynamic information provided by transcranial Doppler (TCD) ultrasonography neuromonitoring (TCDNM) would provide effective monitoring modality for improving outcomes after different types of vascular, neurosurgical, orthopedic, cardiovascular, and cardiothoracic surgeries and some endovascular interventional or diagnostic procedures, like cardiac catheterization or cerebral angiography. Understanding, avoiding, and preventing peri- or postoperative complications, including neurological deficits following abovementioned surgeries, endovascular intervention, or diagnostic procedures, represents an area of great public and economic benefit for society, especially considering the aging population. The American Society of Neurophysiologic Monitoring and American Society of Neuroimaging Guidelines Committees formed a joint task force and developed updated guidelines to assist in the use of TCDNM in the surgical and intensive care settings. Specifically, these guidelines define (1) the objectives of TCD monitoring; (2) the responsibilities and behaviors of the neurosonographer during monitoring; (3) instrumentation and acquisition parameters; (4) safety considerations; (5) contemporary rationale for TCDNM; (6) TCDNM perspectives; and (7) major recommendations.

Giant Aneurysm Management

The treatment of giant aneurysms has always been a challenge in the field of neurovascular disease. Giant aneurysms are larger in size and are associated with thrombosis development and the calcification of the aneurysmal wall and neck, which often interfere with direct clipping. Most giant aneurysms have a wide neck with an incomplete thrombus, making complete embolization almost impossible. Giant aneurysms of different sites have entirely different hemodynamic characteristics. Moreover, aneurysms at the same site may exhibit very different hemodynamics among different individuals. Therefore, careful assessment of each case is required before and during treatment to develop and carry out an individualized treatment plan.

Intraoperative motor-evoked potential monitoring during coil embolization for anterior choroidal artery aneurysms

PURPOSE

Intraoperative motor-evoked potential (MEP) monitoring is widely used in the neck clipping of cerebral aneurysms. Little is known regarding the usefulness of intraoperative MEP monitoring in endovascular aneurysm surgery. The purpose of this study was to validate the feasibility of intraoperative MEP monitoring during the coil embolization of anterior choroidal artery (AChA) aneurysms.

METHODS

Clinical and angiographic data of consecutive patients who underwent coil embolization for unruptured AChA aneurysms with or without intraoperative MEP monitoring between January 2014 and December 2018 at our institute were abstracted and analyzed retrospectively.

RESULTS

Twenty-three unruptured AChA aneurysms were treated. Eleven patients received MEP monitoring, and three of them experienced intraoperative reduction or disappearance of the MEP wave. Even during MEP changes, AChA filling showed no change in any of the three cases. Although one case with MEP monitoring encountered the disappearance of AChA filling, there was no change in MEP. This might be due to retrograde filling of the AChA from the anastomosis with the lateral posterior choroidal artery. AChA blood flow detected by angiography did not always reflect MEP status. When comparing the presence or absence of MEP monitoring, the volume embolization ratio of coiled aneurysms was significantly better in the MEP group.

CONCLUSION

Intraoperative MEP monitoring during endovascular coiling for AChA aneurysms may be feasible. AChA blood flow detected by angiography does not always reflect MEP status.

Kissing Aneurysms: Radiological and Surgical Difficulties in 30 Operated Cases and a Proposed Classification

OBJECTIVE

The first aim of this study is to bring up the radiological and surgical difficulties of kissing aneurysms and to present solutions. The second aim is to develop a classification that can help to predict the difficulties encountered during surgery.

METHODS

The records of 817 patients who were operated on for aneurysm were reviewed retrospectively to identify kissing aneurysms. The radiological and clinical databases of these patients were evaluated in detail.

RESULTS

Kissing aneurysms were detected in 30 patients (3.6%). Radiologically correct diagnosis rate of kissing aneurysms was 80% throughout the series. The most common locations were the anterior communicating artery (12 cases, 40%) and the middle cerebral artery (12 cases, 40.0%). The ruptured aneurysm could not be detected preoperatively in 24% of the patients. Intraoperative rupture occurred in 4 patients (13.3%). Accompanying vascular anomaly/variation was seen in 16 patients (53.3%). As detailed in the text, kissing aneurysms were divided into 3 types according to their position with each other on the parent artery from the surgeon's point of view during surgery: type I (proximal/distal), type II (superior/inferior), and type III (right/left).

CONCLUSIONS

Despite advanced angiographic techniques, even today, kissing aneurysms can be misinterpreted as a single bilobular aneurysm. The ruptured aneurysm may not be detectable preoperatively. These complex aneurysms have a high intraoperative rupture risk. Accompanying vascular anomalies are more common than expected. Clip selection and sequencing are important. Proposed classification helps the surgeon to be aware of intraoperative difficulties that he/she may encounter in advance.

Cerebral venous circulation changes caused by aneurysmal subarachnoid hemorrhage

BACKGROUND

The aneurysmal subarachnoid hemorrhage (aSAH) is an acute severe hemorrhagic stroke with high morbidity and mortality with poor prognosis.

OBJECTIVE

This study aims to analyze the changes of cerebral venous circulation in patients with aneurysmal subarachnoid hemorrhage by digital subtraction angiography (DSA).

MATERIALS AND METHODS

Totally, 57 patients with aSAH, 48 patients with unruptured aneurysms, and 45 patients without aneurysms (control group) were enrolled. The microvascular cerebral circulation time (mCCT), venous cerebral circulation time (vCCT), cerebral arterioles and cortical veins were analyzed by DSA.

RESULTS

There were changes of cerebral microvessels and cortical veins in patients with aSAH. The mCCT (6.15±1.37 s) and vCCT (2.79±0.34 s) of aSAH patients significantly increased compared with control patients (3.74±0.50 s; 2.64±0.32 s) (P < 0.05). However, the mCCT increased more compared with vCCT in aSAH patients (P < 0.001), while the vCCT increased more compared with mCCT in severe aSAH cases (P < 0.01). There was no significant difference in mCCT and vCCT between patients with unruptured aneurysms and controls (P = 0.131; P = 0.621).

CONCLUSIONS

The mCCT increases in acute aSAH patients within 72 hours and vCCT increases in severe aSAH cases.

Prediction of postoperative motor deficits using motor evoked potential deterioration duration in intracranial aneurysm surgery

OBJECTIVE

The study aimed to investigate the predictive value of motor evoked potential (MEP) deterioration duration for postoperative motor deficits in patients undergoing intracranial aneurysm surgery.

METHODS

Data from 587 patients were reviewed and 92 patients with MEP deterioration were enrolled. MEP deterioration duration was compared between patients with and without postoperative motor deficits. Receiver operating characteristic (ROC) curve analysis was performed to define the threshold value for predicting postoperative motor deficit risk. Additionally, the association between MEP deterioration duration and postoperative CT findings was explored.

RESULTS

Patients with postoperative motor deficits had a significantly longer MEP deterioration duration (p < 0.01). An MEP deterioration duration greater than or equal to 13 min was identified as an independent predictor of immediate (p < 0.01), short-term (p < 0.01), and long-term postoperative motor deficits (p < 0.05). There was no significant association between MEP deterioration duration and new CT abnormalities.

CONCLUSION

MEP deterioration duration could be used for predicting intracranial aneurysm surgical outcome.

SIGNIFICANCE

The study first proposed a threshold value of MEP deterioration duration (13 min) for predicting the risk of postoperative motor deficits in patients undergoing intracranial aneurysm surgery.

A pilot study on assessing the role of intra-operative Flow 800 vascular map model in predicting onset of vasospasm following micro vascular clipping of ruptured intracranial aneurysms

Objective To ascertain the predictive value of intra-operative FLOW 800 vascular map model in predicting onset of post-operative clinical vasospasm and delayed cerebral ischemia among patients undergoing micro-vascular clipping of ruptured intracranial aneurysms.  Material and methods A total of 40 patients were enrolled in the study and their variables such as age, World Federation of Neurological Surgeons (WFNS) grade at presentation, Computerized Tomography (CT) Fisher grading, location of the aneurysms, and Indocyanine Green (ICG) flow status were compared and statistically analyzed along with differences in Absorption Intensities (AI) and difference in time lag values obtained from the FLOW 800 vascular map studies for predicting onset of vasospasm.  Results The Receiver Operating curve (ROC) of the model for predicting post-operative vasospasm was highest (.892) for difference in the AI followed by CT Fisher grading (.778), difference in time lag (.700) and WFNS grading (.699).Analysis of variance for different variables studied in our model for predicting vasospasm was significant for all except for age (.991) and the ICG flow through the parent vessel (.079).Multivariate analysis done for predicting the vasospasm was significant for all variables except for age (.869) and ICG main flow (.196) Conclusion Our study confirmed the role of FLOW 800 study model in predicting clinical vasospasm. Inclusion of this entity would therefore help in taking timely and correct therapeutics measures to ensure better patient outcomes.

Early retreatment after surgical clipping of ruptured intracranial aneurysms

BACKGROUND

Although a rerupture after surgical clipping of ruptured intracranial aneurysms is rare, it is associated with high morbidity and mortality. The causes for retreatment and rupture after surgical clipping are not clearly defined.

METHODS

From a prospectively maintained database of 244 patients who had undergone surgical clipping of ruptured intracranial aneurysms, we selected patients who experienced retreatment or rerupture within 30 days after surgical clipping. Aneurysm occlusions were examined by microvascular Doppler ultrasonography and indocyanine green video-angiography. Indications for retreatment included rerupture and partial occlusion. We analyzed the characteristics and causes of early retreatment.

RESULTS

Six patients (2.5%, 95% CI 0.9 to 5.3%) were retreated within 30 days after surgical clipping, including two patients (0.8%, 95% CI 0.1 to 2.9%) who experienced a rerupture. The retreated aneurysms were found in the anterior communicating artery (AcomA) (n = 5) and basilar artery (n = 1). Retreatment of the AcomA (7.5%) was performed significantly more frequently than that of other arteries (0.56%) (p < 0.01). A laterally projected AcomA aneurysm (17.4%) was more frequently retreated than were other aneurysm types (2.3%). Cases of laterally projecting AcomA aneurysms tended to result from an incomplete clip placed using a pterional approach from the opposite side of the aneurysm projection.

CONCLUSIONS

Despite developments, the rates of retreatment and rerupture after surgical clipping remain similar to those reported previously. Retreatment of the AcomA was significantly more frequent than was retreatment of other arteries. Patients underwent retreatment more frequently when they were originally treated for lateral type aneurysms using a pterional approach from the opposite side of the aneurysm projection. The treatment method and evaluation modalities should be considered carefully for AcomA aneurysms in particular.

The Clinical Importance of Perforator Preservation in Intracranial Aneurysm Surgery: An Overview with a Review of the Literature

Clipping for intracranial aneurysms is done to achieve complete occlusion of the aneurysm without a remnant sac. Despite modern advancements of neurosurgical techniques, morbidity related to the clipping of intracranial aneurysms still exists. Clip occlusion of a parent artery or small hidden perforators commonly leads to permanent neurological deficits, and is a serious and unwanted complication. Thus, preserving blood flow in the branches and perforators of a parent artery is very important for successful surgery without postoperative morbidity and mortality. The aim of this review article is to discuss the consequences of perforator injury and how to avoid this phenomenon in aneurysm surgeries using intraoperative monitoring devices.

Intraoperative Combined Use of Somatosensory Evoked Potential, Microvascular Doppler Sonography, and Indocyanine Green Angiography in Clipping of Intracranial Aneurysm

Background

The aim of this study was to evaluate the effect of combining application of somatosensory evoked potential (SEP), microvascular Doppler sonography (MDS), and indocyanine green angiography (ICGA) in intracranial aneurysm clipping surgery.

Material/Methods

A total of 158 patients undergoing an intracranial aneurysm clipping operation were recruited. All patients were evaluated with intraoperative SEP and MDS monitoring, and 28 of them were evaluated with intraoperative combined monitoring of SEP, MDS, and ICGA.

Results

The SEP waves dropped during temporary occlusion of arteries in 19 cases (12.0%), and returned to normal after the clips were repositioned. After aneurysms were clipped, the vortex flow signals were detected by MDS in 6 cases. The aneurysm neck remnants were detected by ICGA in 2 cases of olfactory artery (OA) and in 1 case of middle cerebral artery (MCA), which disappeared after the clips were repositioned. Postoperative CTA or DSA showed that aneurysms were clipped completely and parent arteries and perforating vessels were patent. GOS at 1 month after the surgery was good in 111 cases (70.3%), mild disability in 22 cases (13.9%), severe disability in 14 cases (8.9%), vegetative state in 5 cases (3.2%), and death in 6 cases (3.8%).

Conclusions

Intraoperative combining application of SEP, MDS, and ICGA can reduce brain tissue ischemia and damage and disability and mortality rate after effective clipping of intracranial aneurysms, thereby improving surgical outcomes.

Results of re-exploration because of compromised distal blood flow after clipping unruptured intracranial aneurysms

BACKGROUND

One of the major causes for performing unplanned re-exploration of a craniotomy after microsurgery for unruptured intracranial aneurysms (UIAs) is compromised distal blood flow after clipping. Therefore, it is important to identify the causes of compromised distal blood flow after clipping and the factors that influence the prognosis for re-exploration in order to decrease ischemic complications related to clipping UIAs.

METHOD

Between January 2007 and December 2013, 1954 patients underwent microsurgery for UIAs. In this cohort, 20 patients (1.0%) required unplanned re-exploration of the craniotomy for several reasons, and 11 patients (0.6%) underwent unplanned re-exploration with clip repositioning or changing of the previous clip because of compromised distal blood flow after clipping. Patient characteristics, aneurysm properties, intraoperative findings, annual incidence and prognosis were analyzed in these 11 patients.

RESULTS

The annual incidence of re-exploration has gradually decreased since the introduction of several intraoperative monitoring techniques. In total, 3.0% of UIAs in the M1 trunk, 0.8% of UIAs at the origin of the anterior choroidal artery (AchA) and 0.5% of UIAs at the bifurcation of the middle cerebral artery (MCA) required re-exploration. Here, all 11 UIAs had broad necks, and atherosclerosis was identified around 10 UIAs. Six patients with compromised MCA flow demonstrated relatively better outcomes following re-exploration than five patients with a compromised lenticulostriate artery (LSA) or AchA flow. Four patients with delayed ischemic symptoms demonstrated relatively better outcomes than the seven patients who developed ischemic symptoms immediately postoperatively.

CONCLUSION

Clinicians need to be more careful not to compromise distal blood flow when clipping UIAs at the MCA and AchA origin. Various intraoperative monitoring techniques can help reduce the incidence of compromised distal blood flow after clipping.

Re-exploration of the craniotomy after surgical treatment of unruptured intracranial aneurysms

BACKGROUND

Unplanned re-exploration of the craniotomy after surgical treatment of unruptured intracranial aneurysms (UIAs) is sometimes required, but the underlying causes and rates of these procedures are seldom reported. This study retrospectively analyzed the causes of such re-explorations to identify methods for decreasing their necessity.

METHOD

From January 2000 to December 2011, 1,720 patients with a total of 1,938 UIAs underwent surgical treatment at our institution. From this cohort, 26 patients (1.5 %) with 38 UIAs required re-exploration. Clinical data, aneurysm characteristics, treatment methods, and the incidence and causes of re-exploration of the craniotomy were analyzed for these 26 patients.

RESULTS

Several causes of re-exploration were identified: compromised distal blood flow (eight patients, 0.47 %), hemorrhagic venous infarction (four patients, 0.23 %), brain retraction injury (three patients, 0.17 %), newly identified aneurysms (three patients, 0.17 %), bleeding from an incompletely clipped aneurysm (two patients, 0.12 %), epidural hematoma (two patients, 0.12 %), failed aneurysm clipping (two patients, 0.12 %) and other causes (two patients, 0.12 %). Annual re-exploration incidence rates ranged from 0 to 3.1 %. Annual incidence rates gradually decreased following the introduction of several intraoperative monitoring systems.

CONCLUSIONS

Precise surgical planning and careful operative techniques can reduce the incidence of unplanned re-exploration of the craniotomy. The introduction of various intraoperative monitoring systems can also contribute to a reduction in this incidence.

Microsurgical clipping of previously coiled aneurysms

OBJECTIVE

This study sought to show and analyze the main authors' experience (P.R. and J.M.C.) in previously coiled aneurysm surgery as an emerging challenge in today's neurosurgical practice.

METHODS

Twelve female and 8 male patients, whose ages ranged from 32 to 56 years (average 43.5), underwent surgery between April 2009 and September 2012 in 2 centers. Reasons for surgery were 13 partially occluded aneurysms and 7 recanalized aneurysms.

RESULTS

There was no mortality in this series. Aneurysmal sites were 5 anterior communicating artery aneurysms, 5 posterior communicating artery aneurysms, 3 middle cerebral artery aneurysms, 6 paraclinoid carotid artery aneurysms, and 1 aneurysm in the pericallosal artery. A patient sustained a postsurgical frontal infarction with mild neurological deficit. One of the aneurysms presented with an arterial branch at the level of the aneurysmal neck; therefore, partial clipping and packing was required. Microsurgical clipping in the remaining patients was performed successfully. Eight cases required partial coil removal before clipping.

CONCLUSIONS

Surgical management of previously coiled aneurysms is an emerging challenge in neurosurgery. Incomplete or ineffective embolizations pose an increased risk for the patient, thus requiring surgical treatment. Although not advisable, coil removal might be necessary when in the vicinity of the aneurismal neck in order to place the clip correctly. The authors believe that adequate patient selection and careful preoperative planning are essential to reduce the incidence of patients with unsuccessful coils who will later need surgical treatment.

The role of intraoperative micro-Doppler ultrasound in verifying proper clip placement in intracranial aneurysm surgery

INTRODUCTION

Aneurysmal subarachnoid hemorrhage constitutes a clinical entity associated with high mortality and morbidity. It is widely accepted that improper clip placement may have as a result of incomplete aneurysm occlusion and/or partial or complete obstruction of an adjacent vessel. Various modalities, including intraoperative or postoperative digital subtracting angiography, near-infrared indocyanine green angiography, micro-Doppler ultrasonography (MDU), and neurophysiological studies, have been utilized for verifying proper clip placement. The aim of our study was to review the role of MDU during aneurysmal surgery.

METHODS

A literature search was performed using any possible combination of the following terms: "aneurysm," "brain," "cerebral," "clip," "clipping," "clip malpositioning," "clip repositioning," "clip suboptimal positioning," "Doppler," "intracranial," "microsurgery," "micro-Doppler," "residual neck," "ultrasonography," "ultrasound," and "vessel occlusion". Additionally, reference lists from the retrieved articles were reviewed for identifying any additional articles. Case reports and miniseries were excluded.

RESULTS

A total of 19 series employing intraoperative MDU during aneurysmal microsurgery were retrieved. All studies demonstrated that MDU accuracy is extremely high. The highest reported false-positive rate of MDU was 2 %, while the false-negative rate was reported as high as 1.6 %. It has been demonstrated that the presence of subarachnoid hemorrhage, specific anatomic locations, and large size may predispose to improper clip placement. Intraoperative MDU's technical limitations and weaknesses are adequately identified, in order to minimize the possibility of any misinterpretations.

CONCLUSION

Intraoperative MDU constitutes a safe, accurate, and low cost imaging modality for evaluating blood flow and for verifying proper clip placement during microsurgical clipping.

Monitoring techniques for prevention of procedure-related ischemic damage in aneurysm surgery

OBJECTIVE

To describe the application of intraoperative monitoring techniques during aneurysm surgery and to discuss the advantages and limitations of these techniques in prevention of postoperative neurologic deficits.

METHODS

Articles found in the literature through PubMed for the time frame 1980-2011 and the authors' personal files were reviewed.

RESULTS

Various techniques for detection of vascular insufficiency are available, including direct methods to measure cerebral blood flow and indirect methods to evaluate the integrity of neurologic pathways.

CONCLUSIONS

The choice of monitoring modality should be governed by the vessel and by the vascular territory most at risk during the planned procedure with proper awareness of the potential limits related to each technique. Aneurysm surgery monitoring should help to address issues of continuity and provide a morphologic and functional assessment. Although the use of monitoring devices is still not routine in aneurysm surgery and no standards have been established, combining different monitoring techniques is crucial to optimize aneurysm surgery and avoid or minimize complications.