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

Laser speckle contrast imaging versus microvascular Doppler sonography in aneurysm surgery: A prospective study

Objective

This study aimed to compare microvascular Doppler sonography (MDS) and laser speckle contrast imaging (LSCI) for assessing vessel patency and aneurysm occlusion during microsurgical clipping of intracranial aneurysms.

Methods

MDS and LSCI were used after clip placement during six neurovascular procedures including six patients, and agreement between the two techniques was assessed. LSCI was performed in parallel or right after MDS evaluation. The Doppler response was assessed through listening while flow in the LSCI videos was evaluated by three blinded neurovascular surgeons after the surgery. Statistical analysis determined the agreement between the techniques in assessing flow in 18 regions of interest (ROIs).

Results

Agreement between MDS and LSCI in assessing vessel patency was observed in 87 % of the ROIs. LSCI accurately identified flow in 93.3 % of assessable ROIs, with no false positive or negative measurements. Three ROIs were not assessable with LSCI due to motion artifacts or poor image quality. No complications were observed.

Conclusions

LSCI demonstrated high agreement with MDS in assessing vessel patency during microsurgical clipping of intracranial aneurysms. It provided continuous, real-time, full-field imaging with high spatial resolution and temporal resolution. While MDS allowed evaluation of deep vascular regions, LSCI complemented it by offering unlimited assessment of surrounding vessels.

Intraoperative Neurophysiological Monitoring in Neurosurgery

Intraoperative neurophysiological monitoring (IONM) is a crucial advancement in neurosurgery, enhancing procedural safety and precision. This technique involves continuous real-time assessment of neurophysiological signals, aiding surgeons in timely interventions to protect neural structures. In addition to inherent limitations, IONM necessitates a detailed anesthetic plan for accurate signal recording. Given the growing importance of IONM in neurosurgery, we conducted a narrative review including the most relevant studies about the modalities and their application in different fields of neurosurgery. In particular, this review provides insights for all physicians and healthcare professionals unfamiliar with IONM, elucidating commonly used techniques in neurosurgery. In particular, it discusses the roles of IONM in various neurosurgical settings such as tumoral brain resection, neurovascular surgery, epilepsy surgery, spinal surgery, and peripheral nerve surgery. Furthermore, it offers an overview of the anesthesiologic strategies and limitations of techniques essential for the effective implementation of IONM.

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.

Decibel Decisions: The Concept of Intracranial Aneurysm Surgery With a Decibel Meter on Two Surgical Cases

The present cases were used to investigate the reliability of the intraoperative decibel meter as an objective method of clipping efficiency in cerebral aneurysm surgery and to assess the impact of this method on the surgical procedure itself. Different methodologies have been developed and applied to directly or indirectly evaluate the placement of a clip, for example, intraoperative digital subtraction angiography (DSA), intraoperative micro-Doppler ultrasonography, and, more recently, indocyanine green (ICG). We included two patients with a previously non-treated unruptured brain aneurysm. In both patients, intraoperative micro-Doppler was used in combination with a decibel meter app. Here, we present the cases of two patients. In patient one, the pre-clipping average sound level/equivalent continuous sound pressure level (Avg/Leq) was 96.7 dB, while the post-clipping Avg/Leq was 94.4 dB, indicating a reduction in sound level after clipping. Similarly, the pre-clipping time-weighted average noise level (TWA) was 1.2%, while the post-clipping TWA was 0.5%, indicating a decrease in exposure dose after clipping. In patient two, the average sound level for the post-clipping measurement (94.2 dB) was higher than the pre-clipping measurement (93.5 dB), but the difference was not statistically significant. These cases indicate the potential for using sound measurements as a reliable indicator of adequate aneurysm occlusion during clipping procedures. Further research is needed to confirm these findings.

Enhance Safety in Aneurysm Surgery: Strategies for Prevention of Intraoperative Vascular Complications

Complications during surgery for intracranial aneurysms can be devastating. Notorious pitfalls include premature rupture, parent vessel occlusion, local cerebral injury and brain contusion, and incomplete neck obliteration. These unfavorable intraoperative events can result in major neurological deficits with permanent morbidity and even mortality. Herein, the author highlights the relevant surgical strategies used in his daily practice of aneurysm surgery (e.g., aneurysm clipping with adenosine-induced temporary cardiac arrest), application of which may help prevent vascular complications and enhance surgical safety through reduction of the associated risks, thus allowing improvement of postoperative outcomes. Overall, all described methods and techniques should be considered as small pieces in the complex puzzle of prevention of vascular complications during aneurysm surgery.

Endoscope-assisted microneurosurgery for intracranial aneurysms: A systematic review and meta-analysis

BACKGROUND

In the surgical approach to treat deep-seated intracranial lesions, endoscopes can be used to assist microsurgical operations and improve outcomes. This technique is often called endoscope-assisted microneurosurgery (EAM). This systematic review and meta-analysis aimed to evaluate the feasibility, safety, and effectiveness of EAM.

METHODS

We performed a meta-analysis of relevant articles identified using PubMed, Embase, and the Cochrane Central Register to assess the efficacy of EAM according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) criteria. Primary outcomes were repositioning of the definitive clip, better surgical field, the overall and endoscope-related complication rates, mortality, and the rate of follow up.

RESULTS

A total of 10 studies of 1,432 patients with 1,717 aneurysms treated with EAM were included. EAM led to repositioning of the definitive clip in 13% (95% CI, 9%-17%; I₂ = 72.61%; p < 0.001); 77% of aneurysms treated with endoscopically assisted vision and information had a better outcome than that with standard surgery (95% CI, 52%-95%; I₂ = 97.63%; p < 0.001). There was an overall complication rate of 6% (95% CI, 1%-13%; I₂ = 91.39%; p < 0.001). The incidence of endoscope-related complications was 0% (95% CI, 0%-1%; I₂ = 64%; p < 0.001). The mortality was 0% (95% CI, 0-1%; I₂ = 0.0%); and 94% of patients had an excellent to good recovery and good outcome (95% CI, 88%-98%; I₂ = 88.42%; p < 0.001).

CONCLUSIONS

Our comprehensive study showed that EAM for intracranial aneurysms is feasible, the safety of the surgery is good, and the patients have a good prognosis, Therefore, we think EAM can be more widely adopted in the future.

Continuous blood flow visualization with laser speckle contrast imaging during neurovascular surgery

Significance: Laser speckle contrast imaging (LSCI) has emerged as a promising tool for intraoperative cerebral blood flow (CBF) monitoring because it produces real-time full-field blood flow maps noninvasively and label free. Aim: We aim to demonstrate the ability of LSCI to continuously visualize blood flow during neurovascular procedures. Approach: LSCI hardware was attached to the surgical microscope and did not interfere with the normal operation of the microscope. To more easily visualize CBF in real time, LSCI images were registered with the built-in microscope white light camera such that LSCI images were overlaid on the white light images and displayed to the neurosurgeon continuously in real time. Results: LSCI was performed throughout each surgery when the microscope was positioned over the patient, providing the surgeon with real-time visualization of blood flow changes before, during, and after aneurysm clipping or arteriovenous malformation (AVM) resection in humans. LSCI was also compared with indocyanine green angiography (ICGA) to assess CBF during aneurysm clipping and AVM surgery; integration of the LSCI hardware with the microscope enabled simultaneous acquisition of LSCI and ICGA. Conclusions: The results suggest that LSCI can provide continuous and real-time CBF visualization without affecting the surgeon workflow or requiring a contrast agent. The results also demonstrate that LSCI and ICGA provide different, yet complementary information about vessel perfusion.

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.

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.

Microsurgical Clipping of Carotid-Ophthalmic Tandem Aneurysms: Case Report and Surgical Nuances

Tandem intracranial aneurysms (TandIAs) are rare but inherently complex, and special technical considerations are required for their surgical management. The present case highlights the key surgical aspects of two carotid-ophthalmic TandIAs incidentally found in a 60-year-old female. Both the aneurysms were superiorly projecting, regular in size, and involved the left ophthalmic segment of the internal carotid artery (ICA). The minimum distance between the necks was 3 mm. The patient underwent microsurgery because of the reported major complications rate of the endovascular treatment in the case of a very short minimum distance between the TandIAs. After cervical ICA exposure, both the aneurysms were excluded through a pterional approach. Intradural anterior clinoidectomy and unroofing of the optic canal allowed the mobilization of the left optic nerve. The more distal aneurysm was clipped before the opening of the distal dural ring of the ICA. The proximal aneurysm was clipped with two straight clips stacked perpendicular to the ICA. A small remnant was intentionally left to avoid the stenosis of the ophthalmic artery. Postoperative angiography showed the exclusion of both the aneurysms with a small dog-ear of the more proximal one. The patient was discharged neurologically intact and, after one year, the remnant remained stable. Microsurgical clipping is a definitive and durable treatment for carotid-ophthalmic TandIAs. In the case of a very short minimum distance between the aneurysms, the distal one should be clipped first to make the anterior clinoidectomy, opening of the distal dural ring of the ICA, and clipping of the more proximal aneurysm easier.

Application of the Endoscopic Micro-Inspection Tool QEVO® in the Surgical Treatment of Anterior Circulation Aneurysms-A Technical Note and Case Series

Introduction: The application of neuro-endoscopes in cerebral aneurysm surgery may help to avoid unintended aneurysm remnants and the accidental clipping of perforating arteries and aid the detection of blood collecting in the subdural spaces. Here, we present our experience with the novel endoscopic micro-inspection tool QEVO® (Carl Zeiss Meditec, Germany) in aneurysm surgery.

Materials and Equipment: In all patients the surgical microscope KINEVO® (Carl Zeiss Meditec, Germany) and the Microinspection tool QEVO® were applied.

Methods: The case series comprises 22 unruptured cerebral aneurysms of the anterior circulation. All aneurysms were treated surgically. All patients routinely underwent computed tomography and digital subtraction angiography within 10 days after surgery.

Results: No aneurysm remnants, cerebral ischemic deficits, or subdural hematomas were detected.

Discussion: In this technical note, we discuss the benefits and limitations of the QEVO® tool and illustrate the major paradigms by means of intraoperative photographs.

Adverse intraoperative events during surgical repair of ruptured cerebral aneurysms: a systematic review

Compared with endovascular techniques, clipping of ruptured cerebral aneurysms has been shown to associate with increased morbidity in several studies. Despite this, clipping remains the preferred option for many aneurysms. The objective of this study is to describe the reported adverse events of open repair of ruptured cerebral aneurysms and their impact on patient outcome. The PubMed, Embase and Cochrane databases were searched between June 1999 and June 2019 to identify original studies of at least 100 patients undergoing surgical repair of ruptured cerebral aneurysms and in which adverse event rates were reported. Thirty-six studies reporting adverse events in a total of 12,410 operations for repair of ruptured cerebral aneurysms were included. Surgical adverse events were common with 36 event types reported including intraoperative rupture (median rate of 16.6%), arterial injury (median rate of 3.8%) and brain swelling (median rate 5.6%). Only 6 surgical events were statistically shown to associate with poor outcomes by any author and for intraoperative rupture (the most frequently analysed), there was an even split between authors finding a statistical association with poor outcome and those finding no association. Even with modern surgical techniques, the technical demands of surgical aneurysm repair continue to lead to a high rate of intraoperative adverse events. Despite this, it is not known which of these intraoperative events are the most important contributors to the poor outcomes often seen in these patients. More research directed towards identifying the events that most drive operative morbidity has the potential to improve outcomes for these patients.

Association Between Flow Acceleration in the Carotid Artery and Intracranial Aneurysms

OBJECTIVES

In physiologic pulsatile flow, velocity acceleration is an independent factor determining wall shear stress experienced by the vascular endothelium. The purpose of this study was to evaluate Doppler indices of systolic velocity acceleration in extracranial cerebral vessels and the occurrence of intracranial aneurysms.

METHODS

We reviewed medical records and 3.0-T brain magnetic resonance imaging with 3-dimensional time-of-flight magnetic resonance angiography of 1323 adults who underwent health checkups from June 2006 to November 2011, in whom 53 intracranial aneurysms were identified in 45 patients. Doppler ultrasound parameters of the carotid and vertebral arteries were analyzed in these 45 patients with aneurysms and compared with another 45 control participants matched for age and sex. We defined the maximum systolic acceleration (ACC_max ) as the maximum slope of the early phase of systolic acceleration on the Doppler waveform and the maximum acceleration index (AI_max ) as the ratio of the ACC_max and peak systolic velocity.

RESULTS

The Doppler analysis showed a significantly increased AI_max and ACC_max in the common carotid artery (CCA), internal carotid artery, and vertebral artery in the aneurysm group. A cutoff 13.89 s^-1 for the AI_max of the CCA had sensitivity of 80% with a negative predictive value of 99% for intracranial aneurysms.

CONCLUSIONS

This study suggests that the AI_max of the CCA with a cutoff of 13.89 s^-1 may be an alternative to 3-dimensional time-of-flight magnetic resonance angiography or computed tomographic angiography as a screening tool for intracranial aneurysms. Further prospective studies are needed to validate the diagnostic performance and cost-effectiveness of these indices for screening.

Real-Time Ultrasound Doppler Enhances Precision in Image-Guided Approaches to the Cerebellopontine Angle

OBJECTIVE

To evaluate efficacy and reliability of intraoperative Doppler sonography in localizing the transverse and sigmoid sinuses during lateral suboccipital craniotomy.

METHODS

A 16-Mhz intraoperative micro-Doppler ultrasound (16Mhz, Multi-Dop pro, Compumedics, Singen, Germany) was applied to detect the medial border of the sigmoid sinus and the inferior border of the transverse sinus in 25 patients. Micro-Doppler measurements were compared with magnetic resonance- and computed tomography-based image guidance (Kolibri, Brainlab, Munich, Germany). Visual detectability of the sinuses with the operating microscope was also documented.

RESULTS

Inadvertent incision of the transverse or sigmoid sinuses did not occur in any patient when the 2 localizing methods have been used in combination. The mean mismatch of image-guided system and micro-Doppler was 2.64 mm (range, 0-6 mm; standard deviation, 1.55 mm). With the microscope the transverse sinus was invisible in 7 patients, the sigmoid sinus was visually undetectable in 1 case. The micro-Doppler indicated blood flow outside the visible borders of the sinuses in 5 patients.

CONCLUSIONS

A combination of image-guidance and micro-Doppler enhances the accuracy in localizing the margins of the transverse and sigmoid sinuses using the retrosigmoid approach, thus preventing inadvertent injury. The method could potentially be applied during other craniotomies involving the exposure of a venous sinus.

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.

Intraoperative cerebral blood flow imaging of rodents

Intraoperative monitoring of cerebral blood flow (CBF) is of interest to neuroscience researchers, which offers the assessment of hemodynamic responses throughout the process of neurosurgery and provides an early biomarker for surgical guidance. However, intraoperative CBF imaging has been challenging due to animal's motion and position change during the surgery. In this paper, we presented a design of an operation bench integrated with laser speckle contrast imager which enables monitoring of the CBF intraoperatively. With a specially designed stereotaxic frame and imager, we were able to monitor the CBF changes in both hemispheres during the rodent surgery. The rotatable design of the operation plate and implementation of online image registration allow the technician to move the animal without disturbing the CBF imaging during surgery. The performance of the system was tested by middle cerebral artery occlusion model of rats.

Intraoperative laser speckle contrast imaging with retrospective motion correction for quantitative assessment of cerebral blood flow

Although multiple intraoperative cerebral blood flow (CBF) monitoring techniques are currently available, a quantitative method that allows for continuous monitoring and that can be easily integrated into the surgical workflow is still needed. Laser speckle contrast imaging (LSCI) is an optical imaging technique with a high spatiotemporal resolution that has been recently demonstrated as feasible and effective for intraoperative monitoring of CBF during neurosurgical procedures. This study demonstrates the impact of retrospective motion correction on the quantitative analysis of intraoperatively acquired LSCI images. LSCI images were acquired through a surgical microscope during brain tumor resection procedures from 10 patients under baseline conditions and after a cortical stimulation in three of those patients. The patient's electrocardiogram (ECG) was recorded during acquisition for postprocess correction of pulsatile artifacts. Automatic image registration was retrospectively performed to correct for tissue motion artifacts, and the performance of rigid and nonrigid transformations was compared. In baseline cases, the original images had [Formula: see text] noise across 16 regions of interest (ROIs). ECG filtering moderately reduced the noise to [Formula: see text], while image registration resulted in a further noise reduction of [Formula: see text]. Combined ECG filtering and image registration significantly reduced the noise to [Formula: see text] ([Formula: see text]). Using the combined motion correction, accuracy and sensitivity to small changes in CBF were improved in cortical stimulation cases. There was also excellent agreement between rigid and nonrigid registration methods (15/16 ROIs with [Formula: see text] difference). Results from this study demonstrate the importance of motion correction for improved visualization of CBF changes in clinical LSCI images.

The utility and limitations of intraoperative near-infrared indocyanine green videoangiography in aneurysm surgery

OBJECTIVE

To analyze the clip repositioning rate and the correlation between indocyanine green (ICG) videoangiography and conventional postoperative digital subtraction angiography for completeness of aneurysm occlusion and parent and branching vessel compromise.

METHODS

This retrospective study included 112 patients with 126 aneurysms who underwent microsurgical clipping and ICG videoangiography during aneurysm surgery at a single center from January 2008 to June 2013. Age, gender, aneurysm size, location, and rupture status were included in the model for analysis.

RESULTS

In 10 patients (8%), ICG videoangiography resulted in clip repositioning during surgery. Discordance between ICG videoangiography and postoperative angiography was observed in 5 patients (4%). There was no significant difference of ICG videoangiography-postoperative angiography discordance between ruptured and unruptured aneurysms (P = 0.56). On multivariate analysis, patient age, gender, aneurysm size, and rupture status did not reach significance. Ophthalmic internal carotid artery aneurysms were more likely to have discordance compared with all other aneurysms (P = 0.04; odds ratio, 10.8; confidence interval, 1.5-75.94).

CONCLUSIONS

ICG videoangiography is a very useful modality for intraoperative assessment of the adequacy of aneurysmal obliteration and patency of parent and perforating vessels. However, ICG videoangiography is not absolutely reliable as a stand-alone method during clipping of ophthalmic artery aneurysms and can be complemented with intraoperative digital subtraction angiography. ICG videoangiography can be used either as an alternative or as a complementary technique to intraoperative digital subtraction angiography during aneurysm surgery.

Directional Intraoperative Doppler Ultrasonography During Surgery on Cranial Dural Arteriovenous Fistulas

BACKGROUND:

Directional intraoperative Doppler (dioDoppler) ultrasonography is well established as a tool in the surgery of intracranial aneurysms and cerebral arteriovenous malformations. The literature provides little information about the possible usefulness of this method during surgery on cranial dural arteriovenous fistulas (dAVFs).

OBJECTIVE:

To present our experience with the use of dioDoppler during surgery on cranial dAVFs.

METHODS:

All patients undergoing craniotomy for cranial dAVF from January 2007 to October 2012 in which dioDoppler was used were included in the study. We reviewed patient records, operating protocols, radiological images, dioDoppler files, and intraoperative videos.

RESULTS:

During the study period, 12 patients with cranial dAVFs underwent surgical treatment facilitated by dioDoppler. Four patients were operated on acutely for cerebral bleeds, and 8 patients were treated for various cerebral symptoms and the assumption of a significant risk for intracranial bleed. Three advantages of dioDoppler were unequivocal identification of veins with cortical/deep venous reflux from the fistula, verification of completeness of occlusion of the fistula, and identification of dural arterial feeders not visualized under the microscope.

CONCLUSION:

Reviewing our experience, we found that dioDoppler sonography is an easy, safe, effective, reliable, and instantaneous tool during surgery on cranial dAVFs.

Patterns in neurosurgical adverse events: open cerebrovascular neurosurgery

OBJECT

As part of a project to devise evidence-based safety interventions for specialty surgery, we sought to review current evidence concerning the frequency of adverse events in open cerebrovascular neurosurgery and the state of knowledge regarding methods for their reduction. This review represents part of a series of papers written to consolidate information about these events and preventive measures as part of an ongoing effort to ascertain the utility of devising system-wide policies and safety tools to improve neurosurgical practice.

METHODS

The authors performed a PubMed search using search terms "cerebral aneurysm", "cerebral arteriovenous malformation", "intracerebral hemorrhage", "intracranial hemorrhage", "subarachnoid hemorrhage", and "complications" or "adverse events." Only papers that specifically discussed the relevant complication rates were included. Papers were chosen to be included to maximize the range of rates of occurrence for the reported adverse events.

RESULTS

The review revealed hemorrhage-related hyperglycemia (incidence rates ranging from 27% to 71%) and cerebral salt-wasting syndromes (34%-57%) to be the most common perioperative adverse events related to subarachnoid hemorrhage (SAH). Next in terms of frequency was new cerebral infarction associated with SAH, with a rate estimated at 40%. Many techniques are advocated for use during surgery to minimize risk of this development, including intraoperative neurophysiological monitoring, but are not universally used due to surgeon preference and variable availability of appropriate staffing and equipment. The comparative effectiveness of using or omitting monitoring technologies has not been evaluated. The incidence of perioperative seizure related to vascular neurosurgery is unknown, but reported seizure rates from observational studies range from 4% to 42%. There are no standard guidelines for the use of seizure prophylaxis in these patients, and there remains a need for prospective studies to support such guidelines. Intraoperative rupture occurs at a rate of 7% to 35% and depends on aneurysm location and morphology, history of rupture, surgical technique, and surgeon experience. Preventive strategies include temporary vascular clipping. Technical adverse events directly involving application of the aneurysm clip include incomplete aneurysm obliteration and parent vessel occlusion. The rates of these events range from 5% to 18% for incomplete obliteration and 3% to 12% for major vessel occlusion. Intraoperative angiography is widely used to confirm clip placement; adjuncts include indocyanine green video angiography and microvascular Doppler ultrasonography. Use of these technologies varies by institution.

DISCUSSION

A significant proportion of these complications may be avoidable through development and testing of standardized protocols to incorporate monitoring technologies and specific technical practices, teamwork and communication, and concentrated volume and specialization. Collaborative monitoring and evaluation of such protocols are likely necessary for the advancement of open cerebrovascular neurosurgical quality.

Hemodynamics and changes after STA-MCA anastomosis in moyamoya disease and atherosclerotic cerebrovascular disease measured by micro-Doppler ultrasonography

Moyamoya disease (MMD) and atherosclerotic cerebrovascular disease (ACVD) differ in angiographic appearance and probably hemodynamics. Pediatric MMD (PMMD) usually presents with cerebral ischemia, while intracranial hemorrhage is more common in adult MMD (AMMD), suggesting differences in cerebral hemodynamics. We analyzed the cortical flow velocity and direction of recipient arteries using micro-Doppler ultrasonography to evaluate the cortical circulation before and after anastomosis in MMD and ACVD. Twenty-eight patients with adult MMD (AMMD), 7 with pediatric MMD (PMMD), 16 with ACVD, and 12 control patients were studied. A micro-Doppler probe was applied on the cortical recipient artery (A4 or M4) before and after anastomosis. Systolic maximum flow velocity (V max) and blood flow direction were investigated at proximal and distal parts of anastomosed sites in recipient arteries. Pre- and postoperative regional cerebral blood flow was measured by cold xenon-computed tomography (Xe-CT). Before anastomosis, retrograde cortical flow was significantly more common in PMMD patients, and V max in cortical artery was significantly lower in AMMD patients. Bypass surgery changed the direction of blood flow from the anastomosis site to proximal and distal sites of the recipient artery in most patients, but pre-anastomosis flow direction was preserved more frequently in PMMD patients. The rate of V max increase after anastomosis was significantly higher in AMMD than in PMMD (11.6 ± 9.8 vs. 3.9 ± 1.8; P = 0.01). Micro-Doppler ultrasonography identified differences in cortical circulation among AMMD, PMMD, and ACVD. In AMMD, significantly low velocity in the cortical artery was observed before anastomosis, and bypass surgery reversed the flow and significantly increased flow velocity. The data of PMMD showed unique hemodynamics of the cortical artery before anastomosis, characterized by a higher frequency of retrograde flow and preserved velocity. The V max increase rate was significantly higher in patients with postoperative cerebral hyperperfusion on Xe-CT, and further study is warranted to validate the clinical use of intraoperative micro-Doppler monitoring to predict postoperative hyperperfusion.

Image guidance for transcranial Doppler ultrasonography

BACKGROUND

Transcranial Doppler (TCD) ultrasonography is an important tool for noninvasive detection and monitoring of vasospasm and other pathological conditions of the intracranial vessels.

OBJECTIVE

To demonstrate that image-guided TCD allows rapid identification and blood-flow analysis of specific sections of the vascular anatomy and provides excellent orientation, also allowing diagnostic procedures on pathological vascular structures.

METHODS

Three patients who underwent computed tomographic angiography scanning for reasons not related to this study were examined by neuronavigated image-guided TCD. The Doppler probe was fitted with reflective markers and tracked by a commercially available Kolibri image guidance system.

RESULTS

Image-guided TCD allowed identification of all major intracranial vessels. Unilateral acquisition of reliable Doppler signals for the internal carotid artery, carotid T, middle cerebral artery, middle cerebral artery bifurcation, and anterior cerebral artery required 14 ± 6 minutes. Preregistration of these targets and detection by neuronavigation alone shortened examination times significantly to 8 ± 2 minutes. Registering the optimal examination trajectories on the neuronavigational device and applying navigational pilot software shortened times for repetitive examination further to 4 ± 1 minutes and ensured that the examination was done at the exact same spot under the same angle as in previous examinations.

CONCLUSION

Image guidance can be applied easily and efficiently to TCD. It provides anatomic orientation and may help to standardize investigation protocols, define pathological vascular territories for repeat investigations, and thus reduce interinvestigator variations. Image guidance may also extend the use of TCD to situations of a pathological or variant vascular anatomy.

Intraoperative handheld optical coherence tomography forward-viewing probe: physical performance and preliminary animal imaging

A prototype intraoperative hand-held optical coherence tomography (OCT) imaging probe was developed to provide micron resolution cross-sectional images of subsurface tissue during open surgery. This new ergonomic probe was designed based on electrostatically driven optical fibers, and packaged into a catheter probe in the form factor of clinically accepted Bayonet shaped neurosurgical probes. Optical properties of the probe were measured to have a ~20 μm spot size, 5 mm working distance and 4 mm field of view. Feasibility of this probe for structural and Doppler shift imaging was tested on porcine femoral blood vessel imaging.

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.

Surgical treatment of unruptured intracranial aneurysms in a low-volume hospital--outcome and review of literature

BACKGROUND

The aim of this study was to evaluate surgical outcome of unruptured intracranial aneurysms (UIAs) in a low-volume hospital and compare the results with the recent literature.

METHODS

A retrospective review of all consecutive craniotomies for UIA from July 1999 through June 2009 was performed. Morbidity was defined as modified Rankin Scale (mRS) ≥ 3 and evaluated six weeks after surgery. Cognitive function was evaluated at rehabilitation-to-home discharge. A PubMed database search (2001-2011) seeking retrospective, single-center studies reporting on surgical outcome of UIAs was performed.

RESULTS

There were 47 procedures performed in 42 patients to treat 50 UIAs (mean of 5 annual craniotomies). The mean age was 54.7 ± 12.1 years and mean aneurysm size was 7.6 ± 4.0mm. Favorable outcome (mRS 0-2) at six weeks after surgery was achieved in 45 of 47 procedures (95.7%). Aneurysm size ≥ 12 mm was statistically significant related to adverse outcome defined as mRS change ≥ 1 (71% vs. 29%; p = 0.018). Five patients (10.6%) with favorable neurological outcome (mRS 2) presented with cognitive impairment at rehabilitation-to-home discharge. There was no significant difference in overall morbidity and mortality comparing low- and high-volume hospitals (4.0% vs. 4.8%; p = 0.85).

CONCLUSIONS

Low-volume hospitals may achieve good results for surgical treatment of UIAs. The results indicate that defining numeric operative volume thresholds is not feasible to guide centralization of aneurysm treatment.

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.

Prospective Comparison of Intraoperative Vascular Monitoring Technologies During Cerebral Aneurysm Surgery

BACKGROUND:

Microscope integrated intraoperative near-infrared indocyanine green angiography (ICGA) provides assessment of the cerebral vasculature in the operating field.

OBJECTIVE:

To prospectively compare the value of ICGA-derived information during cerebral aneurysm surgery with data simultaneously generated from other intraoperative monitoring and vascular imaging techniques.

METHODS:

Data from 104 patients with 123 cerebral aneurysms who were operated on were prospectively recorded. Results of intraoperative vascular monitoring and descriptions of how this information influenced intraoperative decision making were analyzed.

RESULTS:

Clip repositioning was necessary in 30 of 123 aneurysms (24.4%) treated. Parent artery occlusion was documented by microvascular Doppler ultrasound in 4 aneurysms. ICGA disclosed parent artery stenoses not detected by sonography in 7 cases. Neuroendoscopy was used in 13 cases of midline aneurysms to confirm perforator patency after clipping, and disclosed aneurysm misclipping undetected by ICGA and digital subtraction angiography in 1 aneurysm. The information from DSA and ICGA corresponded in 120 of 123 aneurysms operated on (97.5 %). In 1 patient, ICGA underestimated a relevant parent artery stenosis detected by digital subtraction angiography. In 2 patients with relevant aneurysmal misclipping, digital subtraction angiography and ICGA led to conflicting results that could be clarified only when both methods were used and interpreted together.

CONCLUSION:

The intraoperative monitoring and vascular imaging methods compared were complementary rather than competitive in nature. None of the devices used were absolutely reliable when used as a stand-alone method. Correct intraoperative assessment of aneurysm occlusion, perforating artery patency, and parent artery reconstruction was possible in all patients when these techniques were used in combination.

Intraoperative computed tomography angiography with computed tomography perfusion imaging in vascular neurosurgery: feasibility of a new concept

OBJECT

In vascular neurosurgery, there is a demand for intraoperative imaging of blood vessels as well as for rapid information about critical impairment of brain perfusion. This study was conducted to analyze the feasibility of intraoperative CT angiography and brain perfusion mapping using an up-to-date multislice CT scanner in a prospective pilot series.

METHODS

Ten patients with unruptured aneurysms underwent intraoperative scanning with a 40-slice sliding-gantry CT scanner. Multimodal CT acquisition was obtained in 8 patients consisting of dynamic perfusion CT (PCT) scanning followed by intracranial CT angiography. Two of these patients underwent CT angiography and PCT 2 times in 1 session as a control after repositioning cerebral aneurysm clips. In another 2 patients, CT angiography was performed alone. The quality of all imaging obtained was assessed in a blinded consensus reading performed by an experienced neurosurgeon and an experienced neuroradiologist. A 6-point scoring system ranging from excellent to insufficient was used for quality evaluation of PCT and CT angiography.

RESULTS

In 9 of 10 PCT data sets, the quality was rated excellent or good. In the remaining case, the quality was rated insufficient for diagnostic evaluation due to major streak artifacts induced by the titanium pins of the head clamp. In this particular case, the quality of the related CT angiography was rated good and sufficient for intraoperative decision making. The quality of all 12 CT angiography data sets was rated excellent or good. In 1 patient with an anterior communicating artery aneurysm, PCT scanning led to a repositioning of the clip because of an ischemic pattern of the perfusion parameter maps due to clip stenosis of an artery. The subsequent PCT scan obtained in this patient revealed an improved perfusion of the related vascular territory, and follow-up MR imaging showed only minor ischemia of the anterior cerebral artery territory.

CONCLUSIONS

Intraoperative CT angiography and PCT scanning were shown to be feasible with short acquisition time, little interference with the surgical workflow, and very good diagnostic imaging quality. Thus, these modalities might be very helpful in vascular neurosurgery. Having demonstrated their feasibility, the impact of these methods on patients' outcomes has now to be analyzed prospectively in a larger series.