Blood flow disturbance in perforating arteries attributable to aneurysm surgery

Prognostic Risk Factors of One-stage Surgical Clipping in aSAH Elderly Patients with MIAs

OBJECTIVE

To discuss the prognostic factors affecting the prognosis of 1-stage surgical clipping in aneurysmal subarachnoid hemorrhage (aSAH) elderly patients with multiple intracranial aneurysms (MIAs).

MATERIALS AND METHODS

A total of 84 elderly patients with aSAH who had MIAs and underwent 1-stage surgical clipping were retrospectively analyzed. Follow-up was conducted with patients 30 days after discharge using the Glasgow Outcome Scale (GOS). A GOS score of 1 to 3 was defined as a poor outcome, and a GOS score of 4 to 5 was defined as a good outcome. General information (gender, age, size of aneurysm, location of rupture of the responsible aneurysm, H-H grade, CT characteristics of aSAH, number of subarachnoid hemorrhages, operation opportunity, postoperative complications, and intraoperative rupture) and complications（cerebral infarction, hydrocephalus, electrolyte disturbance, and encephaledema）were recorded. Univariate analysis and multivariate regression analysis were used to analyze factors that may affect outcomes.

RESULTS

Univariate analysis showed that the number of SAH events ( P =0.005), intraoperative rupture ( P =0.048) and postoperative complications ( P =0.002) were associated with the prognosis of aSAH elderly patients with MIAs undergoing 1-stage surgery. Multivariate analysis showed that the number of SAH events (odds ratio [OR] 4.740, 95% confidence interval [CI] 1.056 to 21.282, P =0.042) and postoperative complications (OR 4.531, 95% CI 1.266 to 16.220, P =0.020) were independently associated with the prognosis of aSAH elderly patients with MIAs undergoing 1-stage surgery.

CONCLUSIONS

The number of SAH events and postoperative complications are independent risk factors for the prognosis of aSAH elderly patients with MIAs undergoing 1-stage surgery. These factors contribute to the timely treatment of potentially related patients.

Usefulness of Transcranial Motor Evoked Potential in Clipping Surgery for Cerebral Aneurysms-Introduction of a New Protocol for Stable Monitoring

The usefulness of transcranial motor evoked potentials (Tc-MEPs) in clipping surgery has been reported. However, numerous false positive and false negative cases were reported. We report the usefulness of a new protocol compared with direct cortical MEP (Dc-MEP).Materials were 351 patients who underwent aneurysmal clipping under simultaneous monitoring of Tc- and Dc-MEPs. A total of 337 patients without hemiparesis and 14 with hemiparesis were separately analyzed. Intraoperative changes of Tc-MEP thresholds were examined in the first 50 patients without hemiparesis. The stimulation strength of Tc-MEP was set at +20% of the stimulation threshold. As thresholds changed intraoperatively, thresholds were examined every 10 min and changed stimulation strength.Stimulation thresholds of Tc-MEP were significantly decreased after craniotomy and significantly increased after CSF aspiration. The recording ratios of Tc- and Dc-MEPs were 98.8% and 90.5%, respectively. Out of 304 patients without MEP change, 5 patients developed transient or mild hemiparesis with infarction of the territory of the perforating artery arising from the posterior communicating artery. Out of 31 patients whose MEP transiently disappeared, 3 patients developed transient or mild hemiparesis. The other two patients without MEP recovery manifested persistent hemiparesis. In 14 patients with preoperative hemiparesis, 3 patients whose healthy/affected ratio of Tc-MEP was large developed severe persistent hemiparesis.We clarified the intraoperative changes of Tc-MEP thresholds for the first time. A new protocol of Tc-MEP that followed thresholds and changed stimulation strength to +20% of thresholds is useful for stable monitoring. The usefulness of Tc-MEP is the same as that or better than that of Dc-MEP.

Endoscope-assisted microsurgical clipping and reduction of post-clipping cerebral infarction: historical comparison using diffusion-weighted images

Endoscopic assistance for aneurysm clipping and its possible benefits have been suggested in previous studies, but its clinical significance has not been fully elucidated. This study aimed to present the efficacy of endoscopy-assisted clipping in reducing post-clipping cerebral infarction (PCI) and clinical outcomes via a historical comparison of patients in our institution from January 2020 to March 2022. A total of 348 patients were included, 189 of whom underwent endoscope-assisted clipping. The overall incidence of PCI was 10.9% (n = 38); it was 15.7% (n = 25) before applying endoscopic assistance and decreased to 6.9% (n = 13) after endoscope application (p = 0.010). The application of a temporary clip (odds ratio [OR]: 2.673, 95% confidence interval [CI]: 1.291-5.536), history of hypertension (OR: 2.176, 95% CI: 0.897-5.279), history of diabetes mellitus (OR: 2.530, 95% CI: 1.079-5.932), and current smoker (OR: 3.553, 95% CI: 1.288-9.802) were independent risk factors of PCI, whereas endoscopic assistance was an independent inverse risk factor (OR: 0.387, 95% CI: 0.182-0.823). Compared to the location of the unruptured intracranial aneurysms, internal carotid artery aneurysms showed a significant decrease in the incidence of PCI (5.8% vs. 22.9%, p = 0.019). In terms of clinical outcomes, PCI was a significant risk factor for longer admission duration, intensive care unit stay, and poor clinical outcomes. However, endoscopic assistance itself was not a significant risk factor for clinical outcomes on the 45-day modified Rankin Scale. In this study, we noted the clinical significance of endoscope-assisted clipping in preventing PCI. These findings could reduce the incidence of PCI and improve the understanding of its mechanisms of action. However, a larger and longer-term study is required to evaluate the benefits of endoscopy on clinical outcomes.

Variations of perforating arteries of anterior communicating artery in cases with anterior communicating artery aneurysms: a cadaveric anatomical study

PURPOSE

In terms of postoperative morbidity and mortality, preservation of the perforating arteries branching from the anterior communicating artery (ACoA) during clipping is particularly imperative in patients with ACoA aneurysm. In the present study, we aimed to investigate whether perforating arteries originated from ACoA were pushed away in a different location in patients with ACoA aneurysm. Furthermore, if they did so, we aimed to identify the direction in which they were dislocated and how the perforating arteries could be preserved during clipping.

METHODS

Herein, we categorized 40 brains obtained from cadavers into two groups. The first (n = 26) and second (n = 14) groups included cases without and with ACoA aneurysms, respectively. After completing the preparation procedure, the brains were dissected using surgical microscope and the relevant anatomical region was examined and photographed. Finally, statistical analyses were performed on the data and the results were documented.

RESULTS

In the aneurysms with posterior and superior projections, the perforators appeared to be pushed away inferiorly and were frequently noted at the anteroinferior part of the aneurysm neck. Most of the cases, where one of the A1s was larger at one side, the perforating arteries arose from the larger A1 side.

CONCLUSION

The mortality and morbidity associated with damage to the perforators can be reduced by approaching the patient from the dominant A1 side and pursuing the perforators primarily at the anteroinferior part of the aneurysm neck in the aneurysms with superior and posterior projections.

Utility of evoked potentials during anterior cerebral artery and anterior communicating artery aneurysm clipping

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For anterior cerebral artery aneurysm clipping dual SSEPs and tcMEPs enhance detection of lower extremity deficits.

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Evoked potentials have limited utility in predicting upper extremity deficits related to subcortical ischemia.

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Four-extremity dual-modality monitoring can also detect pathogenetic mechanisms that are remote from the surgical site.

Objective

To investigate the optimal combination of somatosensory- and transcranial motor-evoked potential (SSEP/tcMEP) modalities and monitored extremities during clip reconstruction of aneurysms of the anterior cerebral artery (ACA) and its branches.

Methods

A retrospective review of 104 cases of surgical clipping of ruptured and unruptured aneurysms was performed. SSEP/tcMEP changes and postoperative motor deficits (PMDs) were assessed from upper and lower extremities (UE/LE) to determine the diagnostic accuracy of each modality separately and in combination.

Results

PMDs were reported in 9 of 104 patients; 7 LE and 8 UE (3.6% of 415 extremities). Evoked potential (EP) monitoring failed to predict a PMD in 8 extremities (1.9%). Seven of 8 false negatives had subarachnoid hemorrhage. Sensitivity and specificity in LE were 50% and 97% for tcMEP, 71% and 98% for SSEP, and 83% and 98% for dual-monitoring of both tcMEP/SSEP. Sensitivity and specificity in UE were 38% and 99% for tcMEP, and 50% and 97% for tcMEP/SSEP, respectively.

Conclusions

Combined tcMEP/SSEP is more accurate than single-modality monitoring for LE but is relatively insensitive for UE PMDs.

Significance

During ACA aneurysm clipping, multiple factors may confound the ability of EP monitoring to predict PMDs, especially brachiofacial hemiparesis caused by perforator insufficiency.

Prediction of Cerebral Aneurysm Hemodynamics With Porous-Medium Models of Flow-Diverting Stents via Deep Learning

The interventional treatment of cerebral aneurysm requires hemodynamics to provide proper guidance. Computational fluid dynamics (CFD) is gradually used in calculating cerebral aneurysm hemodynamics before and after flow-diverting (FD) stent placement. However, the complex operation (such as the construction and placement simulation of fully resolved or porous-medium FD stent) and high computational cost of CFD hinder its application. To solve these problems, we applied aneurysm hemodynamics point cloud data sets and a deep learning network with double input and sampling channels. The flexible point cloud format can represent the geometry and flow distribution of different aneurysms before and after FD stent (represented by porous medium layer) placement with high resolution. The proposed network can directly analyze the relationship between aneurysm geometry and internal hemodynamics, to further realize the flow field prediction and avoid the complex operation of CFD. Statistical analysis shows that the prediction results of hemodynamics by our deep learning method are consistent with the CFD method (error function <13%), but the calculation time is significantly reduced 1,800 times. This study develops a novel deep learning method that can accurately predict the hemodynamics of different cerebral aneurysms before and after FD stent placement with low computational cost and simple operation processes.

Impact of the weekend effect on outcome after microsurgical clipping of ruptured intracranial aneurysms

BACKGROUND

The "weekend effect" describes the assumption that weekend and/or on-call duty admission of emergency patients is associated with increased morbidity and mortality rates. For aneurysmal subarachnoid hemorrhage, we investigated, whether presentation out of regular working hours and microsurgical clipping at nighttime correlates with worse patient outcome.

METHODS

This is a retrospective review of consecutive patients that underwent microsurgical clipping of an acutely ruptured aneurysm at our institution between 2010 and 2019. Patients admitted during (1) regular working hours (Monday-Friday, 08:00-17:59) and (2) on-call duty and microsurgical clipping performed during (a) daytime (Monday-Sunday, 08:00-17:59) and (b) nighttime were compared regarding the following outcome parameters: operation time, treatment-related complications, vasospasm, functional outcome, and angiographic results.

RESULTS

Among 157 enrolled patients, 104 patients (66.2%) were admitted during on-call duty and 48 operations (30.6%) were performed at nighttime. Admission out of regular hours did not affect cerebral infarction (p = 0.545), mortality (p = 0.343), functional outcome (p = 0.178), and aneurysm occlusion (p = 0.689). Microsurgical clipping at nighttime carried higher odds of unfavorable outcome at discharge (OR: 2.3, 95%CI: 1.0-5.1, p = 0.039); however, there were no significant differences regarding the remaining outcome parameters. After multivariable adjustment, clipping at nighttime did not remain as independent prognosticator of short-term outcome (OR: 2.1, 95%CI: 0.7-6.2, p = 0.169).

CONCLUSIONS

Admission out of regular working hours and clipping at nighttime were not independently associated with poor outcome. The adherence to standardized treatment protocols might mitigate the "weekend effect."

Usefulness of Intraoperative Neurophysiological Monitoring During the Clipping of Unruptured Intracranial Aneurysm: Diagnostic Efficacy and Detailed Protocol

Background: Intraoperative neurophysiological monitoring (IONM) has been widely applied in brain vascular surgeries to reduce postoperative neurologic deficit (PND). This study aimed to investigate the effect of IONM during clipping of unruptured intracranial aneurysms (UIAs).

Methods: Between January 2013 and August 2020, we enrolled 193 patients with 202 UIAs in the N group (clipping without IONM) and 319 patients with 343 UIAs in the M group (clipping with IONM). Patients in the M group were intraoperatively monitored for motor evoked potentials (MEPs) and somatosensory evoked potentials (SSEPs). Irreversible evoked potential (EP) change was defined as EP deterioration that did not recover until surgery completion. Sustained PND was defined as neurological symptoms lasting for more than one postoperative month.

Results: Ten (3.1%) and 13 (6.7%) in the M and N groups, respectively, presented with PND. Compared with the N group, the M group had significantly lower occurrence rates of sustained PND [odds ratio (OR) = 0.36, 95% confidence interval (CI) = 0.13–0.98, p = 0.04], ischemic complications (OR = 0.39, 95% CI = 0.15–0.98, p = 0.04), and radiologic complications (OR = 0.40, 95% CI = 0.19–0.82, p = 0.01). Temporary clipping was an independent risk factor for ischemic complications (ICs) in the total patient group (OR = 6.18, 95% CI = 1.75–21.83, p = 0.005), but not in the M group (OR = 5.53, 95% CI = 0.76–41.92, p = 0.09). Regarding PND prediction, considering any EP changes (MEP and/or SSEP) showed the best diagnostic efficiency with a sensitivity of 0.900, specificity of 0.940, positive predictive value of 0.321, negative predictive value (NPV) of 0.997, and a negative likelihood ratio (LR) of 0.11.

Conclusion: IONM application during UIA clipping can reduce PND and radiological complications. The diagnostic effectiveness of IONM, specifically the NPV and LR negative values, was optimal upon consideration of changes in any EP modality.

Cautionary findings for motor evoked potential monitoring in intracranial aneurysm surgery after a single administration of rocuronium to facilitate tracheal intubation

Administration of rocuronium to facilitate intubation has traditionally been regarded as acceptable for intraoperative motor evoked potential (MEP) monitoring because of sufficiently rapid spontaneous neuromuscular blockade recovery. We hypothesized that residual neuromuscular blockade, in an amount that could hinder optimal neuromonitoring in patients undergoing intracranial aneurysm clipping, was still present at dural opening. We sought to identify how often this was occurring and to identify factors which may contribute to prolonged blockade. Records of 97 patients were retrospectively analyzed. Rocuronium was administered to facilitate intubation with no additional neuromuscular blockade given. Prolonged spontaneous recovery time to a train-of-four (TOF) ratio of 0.75 after rocuronium administration was defined as 120 min, which was approximately when dural opening and the setting of baseline MEPs were occurring. Logistic regression analysis was used to identify factors related to prolonged spontaneous recovery time. Prolonged spontaneous recovery time to a TOF ratio of 0.75 was observed in 44.3% of patients. Multivariable analysis showed that only the dosage of rocuronium based on ideal body weight had a positive correlation with prolonged spontaneous recovery time (P = 0.01). There was no significant association between dosage of rocuronium based on total body weight, age, sex, or body temperature and prolonged recovery time. This study demonstrates that the duration of relaxation for MEP monitoring purposes is well-beyond the routinely recognized clinical duration of rocuronium. Residual neuromuscular blockade could result in lower amplitude MEP signals and/or lead to higher required MEP stimulus intensities which can both compromise monitoring sensitivity.

Impact of aneurysm shape and neck configuration on cerebral infarction during microsurgical clipping of intracranial aneurysms

OBJECTIVE

Cerebral infarction is a significant cause of morbidity and mortality related to microsurgical clipping of intracranial aneurysms. The objective of this study was to determine the impact of aneurysm shape and neck configuration on cerebral infarction after aneurysm surgery.

METHODS

The authors retrospectively reviewed consecutive cases of ruptured and unruptured aneurysms treated with microsurgical clipping at their institution between 2010 and 2018. Three-dimensional reconstructions from preoperative computed tomography and digital subtraction angiography were used to determine aneurysm shape (regular/complex) and neck configuration (regular/irregular). Morphological and procedure-related risk factors for cerebral infarction were identified using univariate and multivariate statistical analyses.

RESULTS

Among 243 patients with 252 aneurysms (148 ruptured, 104 unruptured), the overall cerebral infarction rate was 17.1%. Infarction tended to occur more often in aneurysms with complex shape (p = 0.084). Likewise, aneurysms with an irregular neck had a significantly higher rate of infarction (37.5%) than aneurysms with regular neck configuration (10.1%, p < 0.001). Aneurysms with an irregular neck were associated with a higher rate of intraoperative rupture (p = 0.003) and temporary parent artery occlusion (p = 0.037). In the multivariate analysis, irregular neck configuration was identified as an independent risk factor for infarction (OR 4.2, 95% CI 1.9-9.4, p < 0.001), whereas the association between aneurysm shape and infarction was not significant (p = 0.966).

CONCLUSIONS

Irregular aneurysm neck configuration represents an independent risk factor for cerebral infarction during microsurgical clipping of both ruptured and unruptured aneurysms.

Comprehensive analysis of perforator territory infarction on postoperative diffusion-weighted imaging in patients with surgically treated unruptured intracranial saccular aneurysms

OBJECTIVE

Perforator territory infarction (PTI) is still a major problem needing to be solved to achieve good outcomes in aneurysm surgery. However, details and risk factors of PTI diagnosed on postoperative MRI remain unknown. The authors aimed to investigate the details of PTI on postoperative diffusion-weighted imaging (DWI) in patients with surgically treated unruptured intracranial saccular aneurysms (UISAs).

METHODS

The data of 848 patients with 1047 UISAs were retrospectively evaluated. PTI was diagnosed on DWI, which was performed the day after aneurysm surgery. Clinical and radiological characteristics were compared between UISAs with and without PTI. Poor outcome was defined as an increase in 1 or more modified Rankin Scale scores at 12 months after aneurysm surgery.

RESULTS

Postoperative DWI was performed in all cases, and it revealed PTI in 56 UISA cases (5.3%). Forty-three PTIs occurred without direct injury and occlusion of perforators (43 of 56, 77%). Poor outcome was more frequently observed in the PTI group (17 of 56, 30%) than the non-PTI group (57 of 1047, 5.4%) (p < 0.0001). Thalamotuberal arteries (p < 0.01), lateral striate arteries (p < 0.01), Heubner's artery (p < 0.01), anterior median commissural artery (p < 0.05), terminal internal carotid artery perforators (p < 0 0.01), and basilar artery perforator (p < 0 0.01) infarctions were related to poor outcome by adjusted residual analysis. On multivariate analysis, statin use (OR 10, 95% CI, 3.3-31; p < 0.0001), specific aneurysm locations (posterior communicating artery [OR 4.1, 95% CI 2.1-8.1; p < 0.0001] and basilar artery [OR 3.1, 95% CI 1.1-8.9; p = 0.031]), larger aneurysm size (OR 1.1, 95% CI 1.1-1.2; p = 0.043), and permanent decrease of motor evoked potential (OR 38, 95% CI 3.1-468; p = 0.0045) were related to PTI.

CONCLUSIONS

Despite efforts to avoid PTI, it occurred even without direct injury, occlusion of perforators, or evoked potential abnormality. Therefore, surgical treatment of UISAs, especially with the aforementioned risk factors of PTI, should be more carefully considered. The evaluation of PTI in the territory of the above-mentioned perforators could be useful in helping predict the clinical course in patients after aneurysm surgery.

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.

Intraoperative use of transcranial motor/sensory evoked potential monitoring in the clipping of intracranial aneurysms: evaluation of false-positive and false-negative cases

OBJECTIVE

Somatosensory and motor evoked potentials (SEPs and MEPs) are often used to prevent ischemic complications during aneurysm surgeries. However, surgeons often encounter cases with suspicious false-positive and false-negative results from intraoperative evoked potential (EP) monitoring, but the incidence and possible causes for these results are not well established. The aim of this study was to investigate the efficacy and reliability of EP monitoring in the microsurgical treatment of intracranial aneurysms by evaluating false-positive and false-negative cases.

METHODS

From January 2012 to April 2016, 1514 patients underwent surgery for unruptured intracranial aneurysms (UIAs) with EP monitoring at the authors' institution. An EP amplitude decrease of 50% or greater compared with the baseline amplitude was defined as a significant EP change. Correlations between immediate postoperative motor weakness and EP monitoring results were retrospectively reviewed. The authors calculated the sensitivity, specificity, and positive and negative predictive values of intraoperative MEP monitoring, as well as the incidence of false-positive and false-negative results.

RESULTS

Eighteen (1.19%) of the 1514 patients had a symptomatic infarction, and 4 (0.26%) had a symptomatic hemorrhage. A total of 15 patients showed motor weakness, with the weakness detected on the immediate postoperative motor function test in 10 of these cases. Fifteen false-positive cases (0.99%) and 8 false-negative cases (0.53%) were reported. Therefore, MEP during UIA surgery resulted in a sensitivity of 0.10, specificity of 0.94, positive predictive value of 0.01, and negative predictive value of 0.99.

CONCLUSIONS

Intraoperative EP monitoring has high specificity and negative predictive value. Both false-positive and false-negative findings were present. However, it is likely that a more meticulously designed protocol will make EP monitoring a better surrogate indicator of possible ischemic neurological deficits.

A Novel Intraoperative Laser Light Imaging System to Simultaneously Visualize Visible Light and Near-Infrared Fluorescence for Indocyanine Green Videoangiography

Background

Intraoperative indocyanine green videoangiography (ICG-VA) has been reported to be utilized in various cerebrovascular surgeries, wherein the blood flow is noticeably shown in white with a black background. ICG flow alone, but not other structures, can be observed using ICG-VA. We developed a novel high-resolution intraoperative imaging system using laser light source for simultaneously visualizing both visible light and near-infrared (NIR) fluorescence images of ICG-VA.

Methods

We used a novel system for 14 cerebrovascular cases. The operative field was illuminated via an operating microscope using a novel laser light source with four bands at 464 (blue), 532 (green), 640 (red), and 785 nm (NIR region). The observed light from the operative field was split using a beam splitter cube into visible (420– 660 nm) and NIR fluorescence emission light (832–900 nm). Images from the color video and NIR fluorescence emission windows were merged for visualization on a monitor screen simultaneously. Laser light was compared with xenon light, and both setups were tested for cerebrovascular surgeries.

Results

Laser light has numerous advantages over xenon light. The present setup clearly visualized the color operative field with enhanced blood flow. Complete clipping or incomplete clipping with neck remnant or remnant flow into an aneurysm was confirmed in aneurysm surgeries. Feeding arteries and draining veins were easily distinguished in case of arteriovenous malformation.

Conclusions

Using the present setup, we can observe the color operative field and enhanced blood flow using ICG in real time. This setup could facilitate various cerebrovascular surgeries.

Bilateral Infarction of the Recurrent Arteries of Heubner Following Clipping of an Anterior Communicating Artery Aneurysm

A 50-year-old woman reported to the emergency department with thunderclap headache and vomiting. Non-enhanced brain computed tomography (CT) showed a subarachnoid hemorrhage of Hunt-Hess Grade II and Fisher Grade III. Brain angiography CT and transfemoral cerebral angiography (TFCA) revealed an aneurysm of the anterior communicating artery. A direct neck clipping was performed using the pterional approach. The post-operation CT was uneventful. Six days postoperatively, the patient became lethargic. The mean velocity (cm/s) of the middle cerebral artery peaked at 173 cm/s on the right side and 167 cm/s on the left. A TFCA revealed decreased perfusion in both recurrent arteries of Heubner (RAH), but no occlusion in either. Intra-arterial nimodipine injection was administered. On the 7th postoperative day, CT demonstrated a newly developed low-density lesion in the RAH territory bilaterally. The cause of the infarction was attributed to decreased perfusion caused by cerebral vasospasm. The patient was discharged with no definite neurologic deficit except for mild cognitive disorder.

Open-cell stent and use of cone-beam CT enables a safe and effective coil embolization of true ophthalmic artery and anterior choroidal artery aneurysms with preservation of parent vessel: Clinical and angiographic results

Background Treatment of true ophthalmic artery (OA) or anterior choroidal artery (AChA) aneurysms with preservation of the parent vessel may be challenging. Flow diverters have limitations when dealing with branch vessels arising from the aneurysm sac. Visual loss or AChA territory infarcts have been reported both for surgical and endovascular treatment. Methods We evaluated the safety and efficacy of an open-cell design, laser-cut, self-expanding Nitinol stent, and use of cone-beam computed tomography (CBCT) for stent-assisted coil embolization. Results A total of seven patients with unruptured OA or AChA aneurysms were enrolled in this prospective small case study and the data were analyzed retrospectively. A complete obliteration was achieved in all aneurysms immediately post-intervention or at six-month follow-up without any evidence for recanalization at up to three-year follow-up. All patients tolerated the procedure well and there was no change in baseline modified Rankin Scale. Conclusions Our study suggests that specific features of an open-cell stent allow a safe and effective treatment of OA or AChA aneurysms with a high technical success rate and excellent mid-term angiographic and clinical outcome. CBCT is a useful intraoperative imaging tool.

Symptomatic and silent cerebral infarction following surgical clipping of unruptured intracranial aneurysms: incidence, risk factors, and clinical outcome

Cerebral infarction (CI) associated with clipping of unruptured intracranial aneurysms (UIAs) has not been completely studied. The role of individual and operative characteristics is not known, and the risk of silent CI has not been well described. To determine the incidence, risk factors, and clinical outcome of postoperative CI, we retrospectively analyzed 388 consecutive patients undergoing clipping of UIAs between January 2012 and December 2015. We reviewed the pre- and postoperative computed tomography (CT) images of each patient. Postoperative CI was defined as a new parenchymal hypodensity in the vascular territory of treated artery. Patient-specific, aneurysm-specific, and operative variables were analyzed as potential risk factors. Functional outcome at discharge was assessed with the modified Rankin Scale (mRS). Postoperative CI was found in 49 (12.6%) patients, 29 of whom manifested neurological deficits. The incidences of symptomatic stroke and silent CI were 7.5 and 5.2%, respectively. Multivariate analysis showed that larger aneurysm size and history of hypertension were significantly associated with CI. Disability (mRS > 2) rate was 42.9% among patients with CI, which was substantially higher than that among patients without (0.9%). In conclusion, the incidence of CI following clipping of UIAs was not low. Larger aneurysm size and history of hypertension were independent risk factors. Postoperative symptomatic stroke correlated with an extremely high risk of disability. Silent CI was seemingly nondisabling, but the possible cognitive consequence is pending.

Monitoring cerebral ischemia during cerebrovascular surgery

Patients undergoing intracranial cerebrovascular surgery under general anesthesia are at risk of cerebral ischemia due to the nature of the surgery and/or the underlying cerebrovascular occlusive disease. It is thus imperative to reliably and continuously monitor cerebral perfusion during this type of surgery to timely reverse ischemic processes. The aim of this review is to discuss the techniques currently available for monitoring cerebral ischemia during cerebrovascular surgery with a focus on the advantages and disadvantages of each technique.

Intraoperative neuromonitoring during brain arteriovenous malformation microsurgeries and postoperative dysfunction: A retrospective follow-up study

To evaluate the effectiveness of intraoperative neuromonitoring (IONM) during arteriovenous malformation (AVM) surgery, we retrospectively analyzed neurologic dysfunction in patients who underwent AVM surgery with (IONM group) and without IONM (non-IONM group). The sensitivity and specificity of short-term neurologic dysfunction were calculated in the IONM group. IONM parameters were obtained in all patients. There was no significant difference in neurologic dysfunction between patients in the IONM and non-IONM groups. The short-term hemiplegia ratio among grade III patients in the IONM group was significantly lower than the non-IONM group. The sensitivity of IONM for predicting short-term neurologic dysfunction in the IONM group was 86.7% with a specificity of 100%. Of the different parameters monitored intraoperatively, the somatosensory-evoked potential (SEP), maximum expiratory pressure (MEP), and brain auditory-evoked potential (BAEP) may be beneficial in grade III and IV patients. The BAEP complemented the SEP and MEP. Electromyography and the visual-evoked potential have promise in preserving cranial nerve and visual function. For grades I and II patients, no SEP monitoring was safe. For grade V patients, further investigation is required to prevent neurologic dysfunction because of highly related risks for disability and postoperative complications. Moreover, a larger sample size is required to demonstrate the usefulness of IONM during awake craniotomies.

Electrophysiological influence of temporal occlusion of the parent artery during aneurysm surgery

Intraoperative monitoring of the motor evoked potential (MEP) during cerebral aneurysm surgery has been widely used to confirm surgical safety. In this study, we retrospectively analyzed the influence of the MEP amplitude resulting from temporal occlusion of the parent artery, and appropriate judgement in the surgery was discussed. Ten patients underwent temporal occlusion of the parent artery during aneurysm surgery, and five of these patients showed a decrease in the MEP amplitude following temporal arterial occlusion. Clinical factors in patients with and without MEP decrease were compared. The time gap between the surgical procedure and the MEP change and recovery was then investigated. A decrease in the MEP amplitude caused by temporal occlusion had a significantly higher occurrence compared with permanent clip failure. The time from the release procedure to MEP amplitude recovery was relatively longer than the time from the occlusion procedure to the decrease in MEP amplitude. The time from release procedure to MEP amplitude recovery showed a weak correlation with the parent artery occlusion time. There is a time gap between releasing the temporal arterial occlusion and MEP recovery that is similar to temporal parent arterial occlusion and the MEP decrease. The cause of MEP amplitude should be judged carefully, and influence of parent artery temporal occlusion should be taken into consideration during aneurysm clipping.

The Diagnostic Accuracy of Evoked Potential Monitoring Techniques During Intracranial Aneurysm Surgery for Predicting Postoperative Ischemic Damage: A Systematic Review and Meta-Analysis

OBJECTIVE

To investigate the diagnostic accuracy of various evoked potential monitoring techniques in predicting postoperative neurologic deficit in intracranial aneurysm surgery.

METHODS

A literature search of the MEDLINE, Embase, and Cochrane databases was conducted for English language articles published between March 31, 1983 and March 31, 2016. Original studies that reported the use of evoked potential monitoring during intracranial aneurysm surgery in predicting postoperative neurologic damage were selected, and their relevant reference lists were hand searched. Test performance characteristics were summarized using hierarchic summary receiver operating characteristic (ROC) curves and bivariable random-effects models.

RESULTS

Thirteen qualifying studies (1597 patients; 1689 aneurysms) from 6 countries were identified. Eight studies investigated the use of the somatosensory evoked potential (SSEP) monitoring technique, 5 investigated transcranial motor evoked potential (TcMEP) and another 5 investigated direct cortical motor evoked potential (DMEP). Bivariable pooled sensitivity and specificity were 48% (95% confidence interval [CI], 30.7-65.0) and 92% (CI, 88%-94.4%), respectively, for SSEP; 73% (CI, 21.0%-96.7%) and 94% (CI, 87.1%-97.5%) for TcMEP; and 97% (CI, 74.43%-99.99%) and 89% (CI, 84.0%-94.5%) for DMEP. ROC curve analysis showed that TcMEP had the highest accuracy (area under ROC curve 0.95; 95% CI, 0.93-0.97), followed by DMEP (0.91, 0.89-0.94) and SSEP (0.88, 0.85-0.91).

CONCLUSIONS

TcMEP and DMEP have higher diagnostic accuracy than SSEP in predicting postoperative neurologic deficit. The type of anesthetic agent, the use of neuromuscular blocking drugs, and the choice of diagnostic criteria for significant change in cerebral blood flow during aneurysm surgery affect the diagnostic accuracy of evoked potential techniques in predicting postoperative neurologic deficit.

Treatment of Large and Giant Middle Cerebral Artery Aneurysms: Risk Factors for Unfavorable Outcomes

OBJECTIVE

This study aimed to assess the clinical and radiologic outcomes after neurosurgical treatment of large and giant aneurysms of the middle cerebral artery (MCA). In addition, we aimed to identify risk factors for unfavorable outcomes.

METHODS

This retrospective study included 105 patients with 106 large or giant MCA aneurysms treated with neurosurgical methods, including microsurgery and endovascular treatment, over a 15-year period.

RESULTS

The mean aneurysm size was 15.3 ± 7.1 mm. Ten (9.4%) were giant aneurysms. The MCA bifurcation was the most common aneurysm site, followed by the MCA trunk and distal MCA. Aneurysm clipping was the most common treatment method, followed by clipping or trapping with bypass surgery and endovascular treatment. However, acute cerebral infarction was the most common complication (16.0%), poor outcomes (modified Rankin Scale score, 3-6) developed in 12.3% of aneurysms after treatment, and 6.6% of treated aneurysms needed retreatment. Multivariate analysis showed that independent risk factors for acute cerebral infarction after treatment were aneurysms located on the MCA trunk and 2 or more underlying diseases. Initial presentation with subarachnoid hemorrhage and complications during treatment were independent risk factors for poor outcomes. In addition, endosaccular coiling was an independent risk factor for retreatment.

CONCLUSIONS

Neurosurgical management should be considered a priority for large and giant MCA aneurysms because of the high rupture rate and clinical symptoms. However, treatment outcomes remain unsatisfactory. Therefore, tailored management with consideration of risk factors for unfavorable outcomes should be implemented.

Development of and Clinical Experience with a Simple Device for Performing Intraoperative Fluorescein Fluorescence Cerebral Angiography: Technical Notes

To perform intraoperative fluorescence angiography (FAG) under a microscope without an integrated FAG function with reasonable cost and sufficient quality for evaluation, we made a small and easy to use device for fluorescein FAG (FAG filter). We investigated the practical use of this FAG filter during aneurysm surgery, revascularization surgery, and brain tumor surgery. The FAG filter consists of two types of filters: an excitatory filter and a barrier filter. The excitatory filter excludes all wavelengths except for blue light and the barrier filter passes long waves except for blue light. By adding this FAG filter to a microscope without an integrated FAG function, light from the microscope illuminating the surgical field becomes blue, which is blocked by the barrier filter. We put the FAG filter on the objective lens of the operating microscope correctly and fluorescein sodium was injected intravenously or intra-arterially. Fluorescence (green light) from vessels in the surgical field and the dyed tumor were clearly observed through the microscope and recorded by a memory device. This method was easy and could be performed in a short time (about 10 seconds). Blood flow of small vessels deep in the surgical field could be observed. Blood flow stagnation could be evaluated. However, images from this method were inferior to those obtained by currently commercially available microscopes with an integrated FAG function. In brain tumor surgery, a stained tumor on the brain surface could be observed using this method. FAG could be performed with a microscope without an integrated FAG function easily with only this FAG filter.

Ischemic Event and Risk Factors of Embolic Stroke in Atherosclerotic Cerebral Aneurysm Patients Treated with a New Clipping Technique

BACKGROUND

We would like to know the exact rate of ischemic event and the risk factors associated with embolic stroke by treatment of atherosclerotic cerebral aneurysm with a new technique.

METHODS

This is a retrospective cohort study in patients diagnosed as unruptured atherosclerotic cerebral aneurysm who underwent microsurgical clipping between January 2012 and August 2014. All intraoperative video recordings were reviewed and chosen in patients who were identified as atherosclerotic lesion on the dome, neck, or parent artery of the aneurysm. The demographic, radiographic, operative, and postoperative data were collected. The primary end point was the incidence of cerebral infarction and the neurologic outcomes using the discharge modified Rankin Scale (mRS) score at postoperation time. A statistical analysis of the factors associated with embolic stroke was done by Fisher exact and Wilcoxon rank-sum tests. The individual surgical technique was demonstrated as an illustration for use as a guide.

RESULTS

Among 103 atherosclerotic cerebral aneurysms, only 3 patients (2.9%) were associated with postoperative cerebral infarction and 1 of them had permanent neurologic deficit. A good mRS score (0-2) was found in 99% of patients and only 1% had a fair mRS score (3-4). A factor associated with ischemic outcome was duration of operation (P = .046). The differences in the atherosclerotic location showed no statistical significance.

CONCLUSIONS

We found a very low incidence of embolic infarction after clipping of an atherosclerotic cerebral aneurysm with our new technique. Only duration of the operation time was a dependent risk factor for embolic infarction.

Development of a new high-resolution intraoperative imaging system (dual-image videoangiography, DIVA) to simultaneously visualize light and near-infrared fluorescence images of indocyanine green angiography

BACKGROUND

Intraoperative indocyanine green videoangiography (ICG-VA) has been widely used in vascular surgery, where vessels are clearly shown as white on a black background. However, other structures cannot be observed during ICG-VA. We have developed a new, high-resolution intraoperative imaging system (dual-image VA [DIVA]) to simultaneously visualize both light and near-infrared (NIR) fluorescence images from ICG-VA, allowing observation of other structures.

METHODS

The operative field was illuminated via an operating microscope by halogen and xenon lamps with a filter to eliminate wavelengths over 780 nm. In the camera unit, visible light was filtered to 400-700 nm and NIR fluorescence emission light was filtered to 800-900 nm using a special sensor unit with an optical filter. Light and NIR fluorescence images were simultaneously visualized on a single monitor.

RESULTS

Our system clearly visualized the operative field together with fluorescence-enhanced blood flow. In aneurysm surgeries, we could confirm incomplete clipping with the neck remnant or with remnant flow into the aneurysm. In cases of arteriovenous malformation or arteriovenous fistula, feeding arteries and draining veins were easily distinguished.

CONCLUSIONS

This system allows observation of the operative field and enhanced blood flow by ICG together in real time and may facilitate various types of neurovascular surgery.

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.

Microgravity environment and compensatory: Decompensatory phases for intracranial hypertension form new perspectives to explain mechanism underlying communicating hydrocephalus and its related disorders

The pathogenesis underlying communicating hydrocephalus has been centered on impaired cerebrospinal fluid (CSF) outflow secondary to abnormal CSF pulsation and venous hypertension. Hydrodynamic theory of hydrocephalus fares better than traditional theory in explaining the possible mechanisms underlying communicating hydrocephalus. Nonetheless, hydrodynamic theory alone could not fully explain some conditions that have ventriculomegaly but without hydrocephalus. By revisiting brain buoyancy from a fresher perspective, called microgravity environment of the brain, introducing wider concepts of anatomical and physiological compensatory–decompensatory phases for a persistent raise in intracranial pressure, and along with combining these two concepts with the previously well-accepted concepts of Monro–Kellie doctrine, intracranial hypertension, cerebral blood flow, cerebral perfusion pressure, brain compliance and elasticity, cerebral autoregulation, blood–brain and blood–CSF barriers, venous and cardiopulmonary hypertension, Windkessel phenomenon, and cerebral pulsation, we provide plausible explanations to the pathogenesis for communicating hydrocephalus and its related disorders.

Visualization of lenticulostriate arteries at 3T: Optimization of slice-selective off-resonance sinc pulse-prepared TOF-MRA and its comparison with flow-sensitive black-blood MRA

RATIONALE AND OBJECTIVES

To optimize visualization of lenticulostriate artery (LSA) by time-of-flight (TOF) magnetic resonance angiography (MRA) with slice-selective off-resonance sinc (SORS) saturation transfer contrast pulses and to compare capability of optimal TOF-MRA and flow-sensitive black-blood (FSBB) MRA to visualize the LSA at 3T.

MATERIALS AND METHODS

This study was approved by the local ethics committee, and written informed consent was obtained from all the subjects. TOF-MRA was optimized in 20 subjects by comparing SORS pulses of different flip angles: 0, 400°, and 750°. Numbers of LSAs were counted. The optimal TOF-MRA was compared to FSBB-MRA in 21 subjects. Images were evaluated by the numbers and length of visualized LSAs.

RESULTS

LSAs were significantly more visualized in TOF-MRA with SORS pulses of 400° than others (P < .003). When the optimal TOF-MRA was compared to FSBB-MRA, the visualization of LSA using FSBB (mean branch numbers 11.1, 95% confidence interval (CI) 10.0-12.1; mean total length 236 mm, 95% CI 210-263 mm) was significantly better than using TOF (4.7, 95% CI 4.1-5.3; 78 mm, 95% CI 67-89 mm) for both numbers and length of the LSA (P < .0001).

CONCLUSIONS

LSA visualization was best with 400° SORS pulses for TOF-MRA but FSBB-MRA was better than TOF-MRA, which indicates its clinical potential to investigate the LSA on a 3T magnetic resonance imaging.

Relationship between the morphology of A-1 segment of anterior cerebral artery and anterior communicating artery aneurysms

BACKGROUND

The anterior communicating artery (ACoA) is one of the most frequent sites for cerebral aneurysm. The peculiar directions of projection of aneurysms offer great challenges to clinical treatment.

OBJETIVES

To establish the relationship between morphology of A-1 segment of anterior cerebral artery (ACA) and aneurismal projection.

METHODS

Randomly selected digital subtraction angiography data of 264 anterior communicating artery aneurysms (ACoAA) cases and 296 cases of other cerebral vascular diseases in the same period were retrospectively analyzed.

RESULTS

Among 264 ACoAA patients, the morphology of A-1 segment showed type 1a in 158 sides, type 1b in 11, type 2a in 35, type 1 2b in 87, type 3 in 171 and absence in 66. The morphology of A-1 segment in 296 patients with other cerebral vascular diseases displayed type 1a in 195 sides, type 1b in 20, type 2a in 47, type 2b in 74, type 3 in 217 and absence in 39. The non-visualization of A-1 segment in the group of ACoAA occurred more than in the control group (χ(2)=11.482, p=0.001). The classifications of ACoAAs in 264 patients were confirmed as anterior-superior type in 121 cases, anterior-inferior type in 105, complicated type in 16, posterior-inferior type in 12 and posterior-superior type in 10. The correlation between morphology of A-1 segment of ACA and classifications of ACoAA was significant (p=0.000; C=0.619, p=0.000). The direction of ACoAA was downward when the A-1 segment of ACA was Type 1a or Type 2a, and was upward when it was Type 1a or Type 2a and was upward or downward or complicated when it was Type 3.

CONCLUSION

The relationship between morphology of A-1 segment of ACA and classification of ACoAA is clarified in the present study, which is helpful to surgical treatment.

Intra-arterial fluorescence angiography with injection of fluorescein sodium from the superficial temporal artery during aneurysm surgery: technical notes

Intra-arterial fluorescence angiography from a catheter inserted into the external carotid artery (ECA) via the superficial temporal artery (STA) allowed us to satisfactorily evaluate cerebral arterial and venous blood flow. We report this novel method that allowed for repeated angiography within minutes with a low risk of complications due to catheter placement from the STA. The STA was secured at the edge of the standard skin incision during cerebral aneurysm surgery. A 3 Fr catheter was inserted approximately 5 cm to 10 cm into the STA. After manual injection of 5 ml of 20 times diluted 10% fluorescein sodium (fluorescein), fluorescein reached the intracranial internal carotid artery (ICA) through the common carotid artery or anastomoses between the ECA and ICA. Fluorescence emission from the cerebral arteries, capillaries, and veins was clearly observed through the microscope and results were recorded. Quick dye clearance makes it possible to reexamine within 1 minute. In addition, we made a graph of the fluorescence emission intensity in the arteries, capillaries, and veins using fluorescence analysis software. With intravenous fluorescence angiography, dye remains in the vessels for a long time. When repeated examinations are necessary, intervals of approximately 10 minutes are required. There were some cases we could not correctly evaluate with intravenous injection due to weak fluorescence emission. Fluorescence angiography with intra-arterial injection from a catheter inserted into the carotid artery or another major vessel, like conventional angiography, has a risk of procedure-related complications. We report our new method since it solved these problems and is useful.

The significance of intraoperative monitoring of muscle motor evoked potentials during unruptured large and giant cerebral aneurysm surgery

The goal of this study was to characterize the utility of muscle motor evoked potentials (MMEPs) elicited by direct cortical stimulation as a means of monitoring during unruptured large and giant cerebral aneurysm surgery. This analysis focused on intraoperative changes in MMEPs and their relationship to postoperative motor function. The study population consisted of 50 patients who underwent surgery for large (n = 31) or giant (n = 19) cerebral aneurysms. Intraoperative MMEPs were continuously and successfully obtained in muscles belonging to the vascular territory of interest. There was no postoperative motor paresis in 31 (62%) patients in whom intraoperative MMEPs remained unchanged. Transient MMEP change occurred in 15 (30%) of the 50 patients, but 9 of those patients had no postoperative motor deficits, 5 had transient motor deficits, and 1 suffered permanent motor deficits resulting from postoperative delayed blood flow insufficiency due to arteriosclerosis of the parent artery. Permanent MMEP loss occurred in 4 (8%) of 50 patients, all of whom developed severe and permanent postoperative motor deficits. MMEP is a useful monitoring modality in patients undergoing surgery for large or giant cerebral aneurysms. This strategy can help predict functional prognosis or guide the neurosurgeon intraoperatively in an effort to promote better outcomes.

A case of thrombosed giant aneurysm of the azygos anterior cerebral artery: clipping under monitoring of motor evoked potentials of the lower extremities

Giant aneurysms of the distal anterior cerebral artery (ACA), especially the azygos ACA, are rare. We treated a patient with giant aneurysm of the azygos ACA who underwent aspiration of thrombus and clipping under monitoring of motor evoked potentials of the lower extremities (L-MEPs), resulting in remarkable recovery of motor and intellectual function. A 72-year-old male was admitted with left motor weakness persisting for 2 weeks. Neurologically, disorientation and intellectual impairment were also noted. Imaging disclosed a 60-mm diameter aneurysm with heterochronous thrombi arising from the distal bifurcation of the azygos ACA. One month after the onset, radical surgery was scheduled. The azygos ACA was secured and the aneurysm was dissected, and the distal parts of the azygos ACA were confirmed. After removal of the thrombus, the neck was reconstructed with eight clips. L-MEPs disappeared due to occlusion of the azygos ACA for 20 minutes but reappeared after 22 minutes and normalized 78 minutes after reperfusion. Motor weakness improved entirely with mini-mental state examination score of 29 points at 1 month after surgery. One year later, Wechsler Adult Intelligence Scale-Third Edition and Wechsler Memory Scale-Revised scores reached normal levels. Review of reported cases found this aneurysm tends to occur in males in their 50s to 70s presenting with mass sign. Decompression of the aneurysm in the frontal lobe and monitoring of L-MEPs during temporary occlusion of the ACA are important.

Endoscopic indocyanine green video angiography in aneurysm surgery: an innovative method for intraoperative assessment of blood flow in vasculature hidden from microscopic view

Recently, intraoperative fluorescence video angiography using indocyanine green (ICG) has been widely used in aneurysm surgery. This is a simple and useful method to confirm complete occlusion of the aneurysm lumen and preservation of blood flow in the arteries around the aneurysm. However, the observation field of ICG video angiography is limited under a microscope, making it difficult to confirm the flow in the arteries behind the parent arteries or aneurysm. The authors developed a new technique of intraoperative endoscopic ICG video angiography to assess the blood flow in perforating arteries hidden by the parent arteries or aneurysm. The endoscope emits excitation light with a wavelength of approximately 800 nm, and video images were obtained through a cut filter. The authors used this ICG fluorescence endoscope in treating 3 patients with unruptured cerebral aneurysms. During clip placement, the endoscope was inserted to confirm aneurysm occlusion. Then, ICG was intravenously administered, and the fluorescence in the vessels was observed via the endoscope as well as under the microscope. The blood flow in the perforating arteries was clearly identified, and no procedural complication occurred. The authors conclude that the technique is very useful and facilitates intraoperative real-time assessment of the patency of perforating arteries behind parent arteries or aneurysms.

Ischemia changes and tolerance ratio of evoked potential monitoring in intracranial aneurysm surgery

OBJECTIVE

We assessed the relationship between cerebral ischemia-induced changes in evoked potentials and the degree of ischemia tolerance.

METHODS

47 patients underwent somatosensory evoked potential (SEP) and motor evoked potential (MEP) monitoring in intracranial aneurysm surgery. Three duration parameters (time) were recorded: Time 1, from the starting of temporary occlusion unavoidable in aneurysm surgery to the time the evoked potentials decrease from basal level to reaching the warning criterion; Time 2, from evoked potentials reaching the warning criterion to the time the blood flow was resumed; Time 3, after resuming the blood flow, the time it took the evoked potentials to recover to baseline. All three times can be reliably calculated in the SEP recording, but not in the MEP recording which consisted of either unchanged amplitudes or abruptly changing amplitudes, making it impossible to obtain Time 1. The ischemic tolerance ratio (ITR) was calculated as ITR=time 2/time 1×100%. New decreasing myodynamia and fresh infarction after the surgery were employed for evaluating neurological deficits postoperatively, and their correlations with the ischemia-induced changes of evoked potentials recorded during the surgery were analyzed.

RESULTS

We found a change in SEPs in 12 patients whose cerebral ischemia was induced by temporary occlusion of the aneurysm's parent artery. We also found the development of postoperative neurological deficits in 4 patients whose ischemic tolerance ratio (ITR) reached over 80%, while no deficits were found in the other 8 patients whose ITR was less than 50%. MEP changes were seen in 4 patients whose cerebral ischemia was caused by accidentally clamping the perforating branches, causing the development of postoperative neurological deficits but not necessarily leading to significant SEP changes.

CONCLUSION

The Ischemia tolerance ratio (ITR) in SEP recordings is valuable to predicting postoperative neurological deficits caused by temporary occlusion of aneurysm's parent artery. Maintaining the ITR under 50% during operation can effectively avoid postoperative neurological deficits, while an ITR above 80% reliably forecasts postoperative neurological deficits. Complementary to SEPs, MEP recordings are particularly valuable in monitoring ischemic effects caused by accidentally clamping perforating branches. Taken together, this system of monitoring makes it possible to promptly adjust surgery procedures and minimize postoperative neurological deficits.

Impact of Changes in Intraoperative Somatosensory Evoked Potentials on Stroke Rates After Clipping of Intracranial Aneurysms

BACKGROUND:

Somatosensory evoked potential (SSEP) monitoring is used during intracranial aneurysm surgery to track the effects of anesthesia, surgical manipulation, and temporary clipping.

OBJECTIVE:

To present the outcomes of 663 consecutive patients (691 cases) treated surgically for intracranial aneurysms who underwent intraoperative SSEP monitoring and to analyze the sensitivity and specificity of significant SSEP changes in predicting postoperative stroke.

METHODS:

Of 691 surgeries analyzed, 403 (391 anterior circulation, 12 posterior circulation) were unruptured aneurysms and 288 (277 anterior, 11 posterior) were ruptured. Postoperatively, symptomatic patients underwent computed tomography imaging. Positive predictive value, negative predictive value, sensitivity, and specificity were calculated with a Fisher exact test (2-tailed P value).

RESULTS:

Changes in SSEP occurred in 45 of 691 cases (6.5%): 16 of 403 (4.0%) in unruptured aneurysms and 29 of 288 (10%) in ruptured aneurysms. In unruptured aneurysms, reversible SSEP changes were associated with a 20% stroke rate, but irreversible changes were associated with an 80% stroke rate. In ruptured aneurysms, however, reversible changes were associated with a 12% stroke rate, and irreversible changes were associated with a 42% stroke rate. The overall accuracy of SSEP changes in predicting postoperative stroke was as follows: positive predictive value, 30%; negative predictive value, 94%; sensitivity, 25%; and specificity, 95%.

CONCLUSION:

Intraoperative SSEP changes are more reliable in unruptured aneurysm cases than in ruptured cases. Whereas irreversible changes in unruptured cases were associated with an 80% stroke rate, such changes in ruptured cases did not have any adverse ischemic sequelae in 58% of patients. This information is helpful during the intraoperative assessment of reported SSEP changes.

Multiple intraoperative monitoring-assisted microneurosurgical treatment for anterior circulation cerebral aneurysm

This study investigated the efficacy of multiple intraoperative monitoring techniques including indocyanine green angiography (ICGA), somatosensory evoked potential (SSEP) and motor evoked potential (MEP) in the clinical outcome of microneurosurgical treatment for anterior circulation cerebral aneurysm. Fifty-two anterior circulation cerebral aneurysms (Hunt and Hess [H&H] grades 0, 1 or 2) from 45 Chinese in-patients were completely clipped. In one patient, ICGA directed neurosurgeons to readjust aneurysmal clips in order to eliminate a residual aneurysm and restore patency of a branching artery. SSEP/MEP directed neurosurgeons to implement intervention measures in 12 patients for recovery of SSEP/MEP changes, and SSEP/MEP changes partially/totally recovered in 11 of these 12 patients (91.6%). Postoperative motor deficits were observed in three patients, two of which were Glasgow Outcome Scale level 3 (4.4%). In conclusion, for patients with anterior circulation cerebral aneurysm (H&H grade < 3), multiple intraoperative monitoring was beneficial for finding residual aneurysms, detecting ischaemic events in the perforating arteries and reducing severe postoperative motor deficiency.

Bypass or not? Adjustment of surgical strategies according to motor evoked potential changes in large middle cerebral artery aneurysm surgery

OBJECTIVE

To report the use of neuroelectrophysiologic monitoring to alter the course in aneurysm surgery to minimize postoperative infarction and bypass-related adverse events.

METHODS

Two patients with large middle cerebral artery (MCA) aneurysms were admitted to the authors' hospital. Direct clipping seemed to be difficult, and postoperative paralysis was not rare in the authors' experience owing to prolonged temporal occlusion of the parent artery. Balloon test occlusion (BTO) was positive in one patient, who developed paralysis and aphasia 3 minutes after balloon occlusion of the feeding M1 artery. A bypass procedure seemed to be inevitable in both patients. Motor evoked potentials (MEPs) and sensory evoked potentials (SEPs) were used for monitoring during the operation.

RESULTS

For the patient with a positive BTO result, MEP waves did not change until 17 minutes after temporary clip placement. The aneurysm was clipped, and the occlusion time was 24 minutes. MEP waves recovered quickly after reperfusion. In the other patient, there were early changes in MEP waves after temporary clipping. After bypass construction from the temporal artery to the inferior M2 trunk, the time window of safe occlusion was prolonged to 7-8 minutes. Both the aneurysm and the bypassed branch were obliterated, and the clip reconstruction was done to preserve the flow from M1 to the superior M2 trunk. Permanent postoperative disability did not occur in either patient.

CONCLUSIONS

Intraoperative physiologic monitoring is a complementary method to preoperative BTO to evaluate the window of safe occlusion with high reliability.

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.

The use of motor evoked potential monitoring during cerebral aneurysm surgery to predict pure motor deficits due to subcortical ischemia

Subcortical infarcts are most commonly the consequence of perforating artery occlusion and pure motor deficit is the most frequent syndrome resulting from an interruption of the corticospinal tract at the level of the corona radiate, the internal capsule or the brainstem. Motor evoked potential (MEP) monitoring is used as an adjunct to surgery as somatosensory evoked potentials (SEP) have been found to be insensitive to these lesions. Two different techniques have been used for monitoring MEPs during aneurysm surgery: transcranial electrical stimulation (TES) and direct cortical stimulation (DCS). TES may result in patient movement, interfering with microdissection. There is also concern that TES MEP may not detect subcortical motor pathway ischemia by stimulating deeper subcortical structures and may thereby bypass the ischemic area. DCS produces focal muscle activation, less movement and more superficial stimulation that should detect cortical and superficial subcortical ischemia, hence avoiding false-negatives. However, this technique also has disadvantages including subdural bleeding and injury to the brain. Using close-to-motor-threshold stimulation and focal stimulating electrode montages, TES and DCS MEPs do not vary significantly in their capacity to detect lesions of the motor cortex or its efferent pathways. Both techniques are prone to interference by anesthetic agents.

Role of calcification in the outcomes of treated, unruptured, intracerebral aneurysms

PURPOSE

This study examined clinical and aneurysm characteristics in patients with unruptured aneurysms, treated with either coiling or clipping at a single institution, with the primary outcome-Glasgow Outcome Score (GOS)-measured at 6 months after treatment.

METHODS

Data was obtained by a retrospective review of a prospective registry of consecutive cases of unruptured intracranial aneurysms treated at a single institution from 2002 to mid 2007. Demographic data, number, location, and size of aneurysms, calcification, mode of treatment, ASA score, presence of a stroke on post-op imaging, and GOS were recorded. Medical 9.4 for PC was utilized for statistical analysis.

RESULTS

There were 225 procedures performed in 208 patients to treat 252 aneurysms. The mean age was 54.6 years, 74.5% were female, the mean ASA score was 2.45, and 72.2% were smokers. Mean aneurysm size was 8.6 mm. A total of 157 (70%) craniotomies and 68 (30%) coiling procedures were performed. Coiling was utilized more frequently in the posterior circulation [18/32 (56%) posterior circulation, 50/193 (29.9%) anterior circulation, p < 0.001 Chi-square]. Length of hospital stay averaged 5.3 days [6.2 vs. 3.2 clip/coil, p < 0.001, Mann-Whitney]. Overall favorable outcome of GOS 4-5 measured at 6 months post-procedure was 93.3% [145/157 (92.3%) clip, 66/68 (97%) coil, p = 0.3 Chi-square], with a single mortality in the coil group. There was radiographic evidence of a post-procedure stroke on CT in 31 (13.8%) [28/157 (17.8%) clip, 3/68 (4.4%) coil, p < 0.001, Chi-square], but only 11(35%) were symptomatic. All long-term morbidity was attributable to stroke except for one case of late hydrocephalus. Utilizing a logistic regression multivariate analysis (forward), none of the examined factors (age, ASA score, sex, surgeon, posterior circulation, number of aneurysms treated at one sitting, size of aneurysm, smoking status, or type of therapy) related to outcome except calcified aneurysm [20/25 (80%) calcified, 191/200 (95.5%) non-calcified, p < 0.01 Chi-square] with an OR = 7.8 (2.2-28.4, 95% C.I.). Although a univariate analysis of aneurysm size versus outcome achieves statistical significance [p = 0.05, logistic regression (forced)], when the calcified cases are removed from consideration, it does not [p = 0.55, OR = .95, (.82-1.1), 95% C.I.]. Excluding patients with calcified aneurysms resulted in the following calculation of favorable outcome: 94.2% (130/138) clip and 98.4% (61/62) coil [p = 0.33, Chi-square].

CONCLUSIONS

In this study, the presence of calcification in an aneurysm was the sole marker of adverse outcome. Larger aneurysms tended to be more likely to be calcified. Size by itself did not have an adverse affect on outcome. Clipping or clip reconstruction of calcified aneurysms is a significant source of morbidity in the treatment of unruptured aneurysms (Odds ratio 7.8).

The Impact of Minimizing Brain Retraction in Aneurysm Surgery: Evaluation Using Magnetic Resonance Imaging

BACKGROUND:

Recent advances in skull base and microsurgical techniques minimize the need for brain retraction.

OBJECTIVE:

We studied the impact of such techniques in 36 patients (51 aneurysms) using magnetic resonance imaging (MRI).

METHODS:

Preoperative and 24 hours postoperative MR imaging was performed in patients undergoing microsurgical clipping of intracranial aneurysms. Images were evaluated for parenchymal signal changes. During surgery, use and time of brain retraction were recorded. The degree of cortical injury was quantified using a 0 to 3 scale (grade 0 = normal surface; 1 = pial/arachnoidal damage; 2 = gray matter injury; 3 = contusion/necrosis).

RESULTS:

Brain retraction by use of a brain spatula was used in all patients. Retraction times ranged from 14 to 290 minutes (mean, 84.1). Cortical surface changes were grade 0 in 86% and grade 1 in 14%; none showed grade 2 or 3 changes. In the postoperative MRI, 4 patients presented with parenchymal alterations, 4 with edema (11.1%), and 1 patient had additional contusion (2.8%). All lesions were confined to the temporal pole. The grade of cortical surface changes was not related to lesions found on MR imaging. No patients showed retraction-related neurological deficits.

CONCLUSION:

The incidence of evident mechanical parenchymal injury (infarction or contusion) is very low when appropriate microsurgical and skull base techniques are used. Minor pia-arachnoid injury should nevertheless continue to be attended through future advances.

Angiographic characteristics of unruptured middle cerebral artery aneurysms predicting perforator injuries

PURPOSE

The aim of the present study was to delineate preoperative factors that may predict perforator injuries following open surgery for an unruptured middle cerebral artery (MCA) aneurysm.

METHODS

The authors conducted a retrospective review of 85 consecutive patients who underwent surgical clipping of 91 unruptured MCA aneurysms. In addition to demographic profiles, angiographic characteristics of aneurysms, which included the side, size, projection, height from the origin of the ophthalmic artery, and distance between the internal carotid artery (ICA) bifurcation and the aneurysm origin, were analysed and correlated with perforator injuries. Compared with the preoperative CT and/or MRI, any newly-developed infarctions in the striatocapsular area were regarded as perforator injuries even if they were very small and asymptomatic.

RESULTS

A perforator injury was found in 14 out of 91 cases (15%). Although the majority of them remained asymptomatic, neurological deterioration occurred in four patients. Of the analysed variables, both the height (from the origin of the ophthalmic artery) and the distance (between the ICA bifurcation and the aneurysm origin) were significantly associated with perforator injuries. A stepwise increment of the risk was observed as the position of aneurysms became higher or as the distance to the ICA bifurcation became shorter.

CONCLUSIONS

These results would be helpful in estimating surgical risks for an unruptured MCA aneurysm, one of the most commonly encountered aneurysms in the neurosurgical field.

The efficacy of motor-evoked potentials on cerebral aneurysm surgery and new-onset postoperative motor deficits

Surgical clipping may cause stenosis of parent arteries or occlusion of perforating arteries in cerebral aneurysm surgery. To prevent postoperative motor deficits, motor-evoked potentials (MEPs) have been used. This enables to detect cerebral ischemia. However, the rate of false negatives (motor deficits with preserved MEP) has been relatively higher than in aortic surgery. We hypothesized that postoperative motor deficits with preserved intraoperative MEP do not always represent false negatives. We reviewed medical records of patients for cerebral aneurysms surgery with transcranial MEP monitoring from September 2003 to March 2009. We reviewed aneurysm location and size, abnormal computed tomography findings, and clinical outcome. Motor status was evaluated immediately after extubation and anytime when the symptom of motor deficits was found. One hundred and eleven patients underwent cerebral aneurysm clipping with transcranial MEP. Ninety-eight patients manifested no intraoperative MEP changes and no postoperative motor deficits. Six patients showed intraoperative MEP changes, resulting in no motor deficits in 4 patients with MEP recovery and hemiparesis in 2 without MEP recovery. Four patients of 6 had aneurysm in anterior choroidal artery (AchA). Other 6 patients showed postoperative motor deficits despite preserved intraoperative MEP. Two of 6 patients showed no motor deficits just after extubation, but developed deficits 5 hours after coming out of anesthesia. Only 1 of the 6 patients had aneurysm in AchA. In AchA aneurysm surgery, intraoperative MEP monitoring seems to be useful. False negative in MEP monitoring may include new-onset hemiparesis despite preserved intraoperative MEP.