A patient-specific circle of Willis blood flow model in predicting outcomes of balloon test occlusion.

BACKGROUND AND PURPOSE: Balloon test occlusion (BTO) evaluates cerebral ischemic tolerance before internal carotid artery (ICA) sacrifice but carries risks like dissection and thrombosis. This study introduces a new approach using a patient-specific circle of Willis (COW) blood flow model, based on non-invasive quantitative MR angiography (qMRA) measurements, to predict the outcomes of BTO. METHODS: We developed individualized COW blood flow models for 43 patients undergoing BTO. These models simulated blood flow and pressure under normal conditions and with the ICA occlusion. We then compared the model's predictions of blood flow changes due to the simulated ICA occlusion to actual qMRA measurements before the BTO. RESULTS: For all 31 BTO failures, the ipsilateral hemisphere showed an average flow decrease of 15 ± 10% (mean ± standard deviation), compared to 3 ± 2% in the contralateral hemisphere. In all 12 BTO passes, these figures were 6 ± 3% and 1 ± 0.8%, respectively. Notably, all BTO passes had less than a 10% reduction in the ipsilateral hemisphere. In contrast, 65% of BTO failures and 67% single-photon emission computed tomography (SPECT) failures exhibited a decrease of 10% or more in the same region. CONCLUSION: Blood flow reduction exceeding 10% in the ipsilateral hemisphere during BTO is a strong predictor of failure in both BTO and SPECT. Our patient-specific COW blood flow models, incorporating detailed flow and arterial geometry data, offered valuable insights for predicting BTO outcomes. These models are especially beneficial for situations where conducting BTO or SPECT is clinically impractical.

Superficial Temporal Artery-Middle Cerebral Artery Bypass Combined with Internal Carotid Ligation in Treating Complex Internal Carotid Aneurysms. The Willis Polygon Score is an Effective Solution for Developing Countries.

OBJECTIVE: Internal carotid complex aneurysms (ICCAs) management is challenging. Ligating the internal carotid artery (ICA) combined with Superficial Temporal Artery-Middle Cerebral Artery (STA-MCA) anastomosis is an effective treatment option. Balloon test occlusion (BTO) assessments for preoperative decision-making are unaffordable in developing countries. This article discusses the study of Willis polygon (WP) segments as an option and suggests a score for decision-making. Herein, we report the outcomes of a series of patients treated for ICCA aneurysms at a single institution. METHODS: From September 2016 to December 2020, we conducted a retrospective cohort study that analyzed data from patients with ICCAs. Among them, 9 patients received treatment involving ICA ligation combined with STA-MCA anastomosis. Partial or total carotid ligation was determined by using the WP score (WPS). RESULTS: All Patients underwent STA-MCA anastomosis, in addition to total ICA ligation in 7 patients and partial ICA ligation in 2 patients with a WPS of 7 and 5, respectively. Patients with partially ligated carotid arteries were referred to an overseas neurointerventional center 12 months after surgery. As the BTO test was negative, they underwent ICA occlusion by coiling. Postoperative clinical outcomes did not change in 8/9 patients. In 1 patient, we reported a minor parietal stroke; the patient recovered completely after 6 months. Total aneurysm exclusion by thrombosis was achieved in 7/9 patients after total ICA ligation alone and in 2/9 patients after partial ICA ligation combined with coiling. CONCLUSIONS: Limited access to endovascular assessment techniques such as BTO poses challenges in managing ICCAs. The WPS for decision-making appears to be a simple and safe option. In addition to STA-MCA bypass surgery, total or partial ICA ligation may be proposed depending on the WPS. After 12 months, patients with low WPS who underwent partial ICA ligation combined with bypass had postoperative normal BTO.

Preoperative percutaneous Onyx embolization of carotid body paragangliomas with balloon test occlusion.

Objectives: The study aims to analyze our first experience with direct percutaneous embolization of carotid body tumors (CBTs) using ethylene-vinyl alcohol copolymer (Onyx) along with balloon test occlusion (BTO). Methods: A retrospective preliminary single-center study was conducted at the Otorhinolaryngology and Head and Neck Surgery Department and the Medical Imaging Department of the University Teaching Hospital. A consecutive series of three patients with CBTs was treated at the local institution between October 2018 and June 2019. All three patients underwent preoperative percutaneous embolization using ethylene-vinyl alcohol copolymer (Onyx 18) with the addition of BTO. Outcome measures were the percentage of tumor devascularization, intraoperative blood losses, and operation times. BTO was evaluated by clinical neurological examination and neurosonological transcranial Doppler examination of the middle cerebral artery (MCA). Results: Devascularization of all three tumors was complete or near complete. All three tumors were surgically extirpated with excellent surgical outcomes. The blood losses were minimal, and the average operation time was 2 h and 8 min. BTO was positive in one patient, which was valuable additional information on carotid branches ligation limitations. The other two patients showed negative BTOs with the result of safety of eventual carotid arteries ligations. Conclusion: Preoperative direct percutaneous embolization of CBT with Onyx is a highly effective procedure that significantly facilitates surgery. BTO provides valuable additional information on the most appropriate and safe surgical approach.

Venous balloon test occlusion for pulsatile tinnitus assessment: A clinical feasibility study.

BACKGROUND: Pulsatile tinnitus (PT) can have huge impact on the patients' quality of life and can be associated with curable vascular anomalies. In the present study, we aim firstly to describe our protocol for venous BTO and secondly to report possible predictors for a positive BTO test. METHODS: All consecutive PT patients undergoing BTO for the purpose of determining eligibility for venous neuro-intervention were included. We recommend BTO for patients when there is uncertainty in the association of the venous pathology identified on non-invasive cross-sectional imaging (CTV or MRV) and the patient's symptoms. RESULTS: Between May 2016 and October 2022, we recorded 29 venous balloon test occlusions fulfilling our inclusions criteria. Over the 29 procedures scheduled, 8 finally did not lead to a successful balloon test occlusion. The main reason was that the patient did not hear the PT on the day the angiogram was performed. Two patients could not have the BTO due to difficulties in venous navigation. After BTO, only four patients of our cohort were scheduled for an endovascular treatment. CONCLUSION: We describe a technique and present a single cohort of venous BTO in severe PT patients with unclear anatomical cause. This angiographic test was useful to exclude patients from endovascular surgery and discuss the most probable cause of the PT. Complexity of vascular PT should support a patient-based approach when discussing interventional treatment.

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

BACKGROUND: Parent artery occlusion (PAO) is an effective treatment for hemorrhagic diseases associated with the internal carotid artery. There are several reports of long-term cerebral infarction or the formation of de novo cerebral aneurysms following PAO. MATERIALS AND METHODS: We retrospectively reviewed these complications in 38 patients who underwent PAO for therapeutic treatment. We investigated perioperative cerebral infarctions, long-term cerebral infarctions, and de novo aneurysms. RESULTS: The mean age of the patients was 64.0 years, and 25 patients (65.8%) were female. The causative diseases were unruptured (n = 19; 50.0%) and ruptured (n = 8; 21.1%) aneurysms. PAO was performed after ischemic tolerance was assessed with balloon test occlusion (BTO), and BTO was performed in 34 patients, of whom 25 (73.5%) had ischemic tolerance. Twenty-six patients (68.4%) were treated with PAO alone, eight (23.5%) with low-flow bypass, and six (17.6%) with high-flow bypass. Perioperative complications occurred in five patients (13.2%): two of the 26 patients (7.7%) who underwent scheduled treatment and three of the 12 patients (25.0%) who underwent emergency treatment. One patient (2.6%) had long-term de novo aneurysm, and none developed cerebral infarction. CONCLUSIONS: These results showed that the assessment of ischemic tolerance by performing BTO and appropriate revascularization in scheduled treatments are important to reduce perioperative and long-term cerebral infarctions. PAO must be performed with greater caution in emergency treatment.

Emergency extra-intracranial bypass surgery in a patient with neurologic deficit after an accident in carotid occlusive test: A case report.

OBJECTIVE: BTO is the procedure performed to assess the collateral circulation within the Willis circle in a giant ICA aneurysm. An ICA occlusion after BTO is very rare. We present a case of an internal carotid artery occlusion as a complication of BTO that required urgent revascularization surgery. CASE PRESENTATION: A 56-year-old female with a history of transient ischemic attacks for one year was diagnosed with multiple aneurysms: a giant aneurysm of the left supra-clinoid ICA, two small ones on left MCA and right ophthalmic. A BTO was performed to assess collateral supply and determine whether bypass surgery should be necessary. During the procedure, the balloon was detached while insufflating, and the patient had a subsequent neurological decline consistent with an MCA syndrome. EC-IC bypass surgery was performed with an end-to-side anastomosis of STA-MCA by trapping the giant aneurysm and clipping the ipsilateral MCA aneurysm. The patient had a reversal of neurological symptoms and made an uneventful recovery. DISCUSSION: We discuss the epidemiology of giant ICA aneurysms, the indications for BTO, and its complication. Emergency intracranial and extracranial bypass surgery in case of acute ICA injury is also discussed. We also highlighted the attributable factors to treatment strategies under restrictive conditions in Vietnam. CONCLUSIONS: ICA occlusion due to insufflated balloon detachment is an unreported complication in literature. Emergency bypass surgery is a potential treatment choice for this unusual iatrogenic complication.

Complex Intracranial Aneurysms.

Complex intracranial aneurysms remain challenging to treat using standard microsurgical or endovascular techniques. These aneurysms often require a combination of deconstructive and reconstructive procedures, such as parent artery occlusion, flow alteration, and blind-alley formation with or without bypass surgery, for effective and enduring therapeutic effects. It is important to determine the type of bypass based on the site of occlusion of the patent artery, anatomical features of the distal vessels, and expected adequate blood flow. In this chapter, we describe the "Standards," "Advances," and "Controversies" in the context of a microsurgical treatment strategy for complex intracranial aneurysms. "Standards" include a combination of frequent and commonly used procedures that have been gathering a certain consensus on their effectiveness. "Advances" include infrequent, demanding, and/or uncertain surgical procedures that are currently under debate. Finally, "Controversies" discuss a number of unsolved issues.

Super-selective balloon test occlusion with electrophysiological monitoring to occlude angiographically invisible posterior communicating artery perforators with unruptured aneurysm.

Balloon test occlusion (BTO) can predict the ischemic complication risk associated with arterial occlusion. We present a case of an unruptured, broad-necked internal carotid artery-posterior communicating artery (PcomA) aneurysm that was successfully embolized after super-selective BTO of fetal PcomA with electrophysiological monitoring. The proximal portion of the PcomA was internally occluded without causing major neurological deficits, although we observed a small new infarction in the ipsilateral anterior thalamus postoperatively. We recognized small perforators arising from the proximal PcomA during a previous clipping surgery. Super-selective BTO with electrophysiological monitoring could be useful for functional preservation after infarction from angiographically invisible perforators.

A novel endovascular treatment for true ophthalmic aneurysms: A case report.

Introduction: Cerebral aneurysms located along the internal carotid artery at the origin of the ophthalmic artery can be treated through open surgery or endovascular technique. The former affords more certainty of aneurysm obliteration, while the latter poses less risk to vision. Flow diversion is an increasingly accepted treatment for side-wall carotid aneurysms, although location at the branch point of the ophthalmic artery is known to moderate occlusion outcomes. Case presentation: We present a case of a middle-aged female patient with a morphologically irregular 4-mm ophthalmic artery aneurysm (OphA) and a smaller superior hypophyseal artery (SHA) aneurysm whose successful and uncomplicated obliteration by flow diversion with adjunctive coiling was predicted via a balloon test occlusion (BTO). BTO was employed prior to stent placement to confirm a) ophthalmic artery distal collateralization with external carotid artery (ECA) branches and b) preserved arterial flow in the retina visualized via fundoscopy. At 1 year following angiography, the patient had no postoperative deficits and benefitted from complete occlusion of the OphA and SHA. Conclusion: OphAs constitute a complex surgical disease that is historically associated with high visual morbidity. We present a novel advanced endovascular technique of BTO followed by flow diversion with adjunctive coiling that successfully obliterated an OphA while preserving vision.

Virtual test occlusion for assessing ischemic tolerance using computational fluid dynamics.

BACKGROUND: Ischemic tolerance has been evaluated by the balloon test occlusion (BTO) for cerebral aneurysms and tumors that might require parent artery occlusion during surgery. However, because of its invasiveness, a non-invasive evaluation method is needed. In this study, we assessed the possibility of virtual test occlusion using computational fluid dynamics (CFD) as a non-invasive alternative to BTO for evaluating ischemic tolerance. METHODS: Twenty-one patients who underwent BTO were included in the study. Virtual test occlusion was performed using CFD analysis, and the flow rate (FR) and wall shear stress (WSS) of the middle cerebral artery on the occlusion side were calculated. The correlations between these parameters and examination data including the parameters of computed tomography perfusion during BTO were assessed and the cutoff value of CFD parameters for detecting the good collateral group was calculated. RESULTS: The FR was strongly correlated with mean transit time (MTT) during BTO and moderately correlated with collateral flow grade based on angiographic appearance. The WSS was moderately correlated with collateral flow grade, mean stump pressure (MSP), and MTT. Furthermore, the FR and WSS were strongly correlated with the total FR and the diameters of the inlet vessels. The cutoff value of FR for detecting the good collateral group was 126.2 mL/min, while that of the WSS was 4.54 Pa. CONCLUSION: The parameters obtained through CFD analysis were correlated with collateral flow grade and MSP in addition to MTT. CFD analysis may be useful to evaluate ischemic tolerance as a non-invasive alternative to BTO.

Balloon Test Occlusion of Internal Carotid Artery in Recurrent Nasopharyngeal Carcinoma Before Endoscopic Nasopharyngectomy: A Single Center Experience.

OBJECTIVES: Endoscopic nasopharyngectomy (ENPG) is a promising way in treating recurrent nasopharyngeal carcinoma (rNPC), but sometimes may require therapeutic internal carotid artery (ICA) occlusion beforehand. Balloon test occlusion (BTO) is performed to evaluate cerebral ischemic tolerance for ICA sacrifice. However, absence of neurological deficits during BTO does not preclude occur of delayed cerebral ischemia after permanent ICA occlusion. In this study, we evaluate the utility of near-infrared spectroscopy (NIRS) regional cerebral oxygen saturation (rSO2) monitoring during ICA BTO to quantify cerebral ischemic tolerance and to identify the valid cut-off values for safe carotid artery occlusion. This study also aims to find out angiographic findings of cerebral collateral circulation to predict ICA BTO results simultaneously. MATERIAL AND METHODS: 87 BTO of ICA were performed from November 2018 to November 2020 at authors' institution. 79 angiographies of collateral flow were performed in time during BTO and classified into several Subgroups and Types according to their anatomic and collateral flow configurations. 62 of 87 cases accepted monitoring of cerebral rSO2. Categorical variables were compared by using Fisher exact tests and Mann-Whitney U tests. Receiver operating characteristic curve analysis was used to determine the most suitable cut-off value. RESULTS: The most suitable cut-off △rSO2 value for detecting BTO-positive group obtained through ROC curve analysis was 5% (sensitivity: 100%, specificity: 86%). NIRS rSO2 monitoring wasn't able to detect BTO false-negative results (p = 0.310). The anterior Circle was functionally much more important than the posterior Circle among the primary collateral pathways. The presence of secondary collateral pathways was considered as a sign of deteriorated cerebral hemodynamic condition during ICA BTO. In Types 5 and 6, reverse blood flow to the ICA during BTO protected patients from delayed cerebral ischemia after therapeutic ICA occlusion (p = 0.0357). In Subgroup IV, absence of the posterior Circle was significantly associated with BTO-positive results (p = 0.0426). CONCLUSION: Angiography of cerebral collateral circulation during ICA BTO is significantly correlated with ICA BTO results. Angiographic ICA BTO can be performed in conjunction with NIRS cerebral oximeter for its advantage of being noninvasive, real-time, cost-effective, simple for operation and most importantly for its correct prediction of most rSO2 outcomes of ICA sacrifice. However, in order to ensure a safe carotid artery occlusion, more quantitative adjunctive blood flow measurements are recommended when angiography of cerebral collateral circulation doesn't fully support rSO2 outcome among clinically ICA BTO-negative cases.

Ophthalmic Artery Flow Pattern-related Stump Pressure and Ischemic Tolerance during Balloon Test Occlusion of the Internal Carotid Artery.

Very few studies have described the blood flow pattern in the ipsilateral ophthalmic artery (OphA) during internal carotid artery (ICA) balloon test occlusion performed to estimate the risk of cerebral ischemia associated with therapeutic ICA sacrifice. This study aimed to investigate the relationship between ipsilateral OphA flow patterns just after ICA temporary occlusion and balloon test occlusion findings. We retrospectively reviewed 32 balloon test occlusion procedures performed at our institution between 2010 and 2019, and analyzed the OphA flow patterns and the conventional balloon test occlusion assessment items: neurological symptoms, stump pressure, stump-pressure ratio, collateral circulations, and venous phase delay. The flow patterns were categorized as type I (retrograde flow reaching the middle cerebral artery [MCA]), type II (retrograde flow to the ICA not reaching the MCA), or type III (no retrograde flow). Tolerance to balloon test occlusion was observed in 4/21 patients (19.0%), 4/6 patients (66.7%), and all five patients with types I, II, and III flows, respectively. The mean pressure ratios during balloon test occlusion in flow types I, II, and III were 35.6% ± 3.5%, 56.4% ± 6.5%, and 69.4% ± 7.1%, respectively (P <0.001). The mean stump pressures in flow types I, II, and III were 36.2 ± 3.6 mmHg, 46.6 ± 6.7 mmHg, and 66.6 ± 7.3 mmHg, respectively (P = 0.003). The mean venous phase delay in flow types I, II, and III were 0.99 ± 0.14 s, 0.25 ± 0.25 s, and 0.0 ± 0.28 s, respectively (P = 0.004). All the above variables showed significant flow-related differences. These results suggest that the OphA flow patterns may provide an additional diagnostic criterion for balloon test occlusion.

Recovery of Visual Loss Following Internal Trapping of Anterior Cerebral Artery (A1 Segment) for Partially Thrombosed Large Anterior Communicating Artery Aneurysm: A Case Report.

A 60-year-old woman, who experienced progressive right visual loss, was diagnosed with an unruptured large cerebral aneurysm. Magnetic resonance imaging (MRI) and angiography revealed a large partially thrombosed anterior communicating artery (Acom) aneurysm. The aneurysmal neck was located at the junction of the left A1-A2 segments, and the aneurysmal dome communicated with the right A1-A2 junction by the Acom. Endovascular treatment using the flow alteration technique was selected. Following an oral antiplatelet therapy for 9 days, balloon test occlusion (BTO) of the medial portion of the left A1 segment was performed under local anesthesia. After confirming the tolerance of the BTO, internal trapping of the medial portion of the left A1 segment by detachable coils was performed following intra-aneurysmal coil embolization. Oral antiplatelet treatment was continued for 19 days postoperatively. Within 3 months following the operation, her right visual acuity dramatically improved to the original level. Owing to aneurysmal recanalization and the disappearance of the thrombus, the second and third embolization was performed through the Acom route, 4 months and 3 years following the first embolization, respectively, and followed up for an additional 7 years by MRI; no deterioration of her visual acuity and no aneurysmal recanalization was observed. Thus, endosaccular embolization combined with flow alteration is considered a useful alternative treatment for large and partially thrombosed Acom aneurysms.

Repair of internal carotid artery injury with aneurysm clip during endoscopic endonasal surgery: illustrative case.

BACKGROUND: One of the most feared and dangerous scenarios that can appear during an endoscopic endonasal surgery (EES) is the iatrogenic injury of the internal carotid artery (ICA). Several methods, along with a variety of outcomes, have been described to deal with this complication. To the authors' knowledge, this is the first report on the use of a Yasargil-type aneurysm clip to solve an ICA injury, preserving the artery's patency and having a long-term follow-up. The authors discuss the advantages and disadvantages of other vessel preservation techniques compared with clipping. OBSERVATIONS: A visually impaired 56-year-old woman was diagnosed with a giant nonfunctional pituitary tumor that invaded the sphenoidal sinus, anterior and posterior ethmoidal cells, and both cavernous sinuses, with suprasellar extension and optochiasmatic compression. The patient underwent EES, and during the final resection phase her left ICA was injured, with massive hemorrhage. LESSONS: ICA injury during endoscopic skull base surgery carries high mortality and morbidity; it is essential to maintain carotid flow when possible to avoid short-term and long-term consequences. There are several techniques depicted in the literature to deal with this situation. The authors report the use of a Yasargil mini-clip to deal with the injury for a positive outcome: primary hemostasis, vessel preservation, and no postoperative complications.

Dissecting aneurysms of the posterior cerebral artery - A retrospective review of imaging, angiographic characteristics, endovascular management and outcome.

PURPOSE: To review management, clinical and imaging outcomes of dissecting posterior cerebral artery (PCA) aneurysms with emphasis on endovascular management in the form of parent vessel occlusion (PVO) at a tertiary care center. METHODS: Thirty-six dissecting PCA aneurysms (19 ruptured) encountered at our center between January 2013 and November 2019 were reviewed for aneurysm location/size/presence of fetal PCA/management. Postprocedural imaging of patients who underwent endovascular intervention was reviewed for PCA territory infarcts and clinical records assessed for presence of neuro-deficits and outcome. None of the patients underwent a balloon test occlusion (BTO) prior to PVO. RESULTS: The location of the aneurysms was as follows-P1 = 8/P1-P2 = 11/P2 = 5/P2-P3 = 10/P3 = 2. The mean size was 11.7x6.8 mm. Endovascular intervention was carried out in 20 patients in the form of PVO with coiling in 16 patients, coiling alone in 3 patients, and reconstruction of the left PCA with flow diverter deployment in one patient. Postprocedural PCA territory infarct was seen in 5 cases of PVO out of which 4 had a good functional recovery. Overall, 15/16 patients (93.7%) who underwent PVO had mRS ≤ 2 on follow-up. The single case with flow diverter also developed an infarct and had adverse outcome on follow up. CONCLUSION: Among the various management strategies for dissecting PCA aneurysms, PVO is feasible and relatively safe even in absence of BTO in scenarios like critically ill patients with ruptured aneurysms, difficult access and financial constraints. Thromboembolic complications and antiplatelet therapy is a concern in reconstructive strategies.

Coil Occlusion of Right M2 Fusiform Aneurysm After Balloon-Test Occlusion: 2-Dimensional Video.

We present a 73-year-old man with an incidental right M2 fusiform aneurysm demonstrating growth on serial noninvasive imaging over 5 years (Video 1). After multidisciplinary conference review, the decision was to proceed with intracranial balloon-test occlusion (BTO) followed by coil occlusion if the patient passed this test or by trap and bypass if the patient failed this test. With the patient under moderate conscious sedation, a transfemoral 8F approach was used with positioning of a TracStar 95-cm 088 guide catheter (Imperative Care, Campbell, California, USA) into the distal right cervical ICA. We positioned a Scepter 4-mm × 10-mm compliant dual-lumen balloon microcatheter (MicroVention, Alisa Viejo, California, USA) into the proximal M2. The patient passed the 30-minute BTO including a 15-minute hypotensive challenge with nitroprusside infusion. Our goal was to occlude the aneurysm from distal to proximal for precise thrombosis. A Phenom 17 150-cm microcatheter (Medtronic, Dublin, Ireland) separate from the Scepter balloon microcatheter was positioned in the distal portion of the aneurysm. Coil occlusion was successfully performed with an assortment of complex and helical coils. Sluggish anterograde flow was seen distal to the aneurysm with prominent retrograde filling of the distal right MCA territory via pial collaterals from the right PCA. The patient tolerated the procedure well and was discharged the following day neurologically intact. Six-month follow-up diagnostic angiogram confirmed complete occlusion of the aneurysm. This is the first published video using the elegant approach of intracranial BTO followed by coil occlusion for an intracranial fusiform aneurysm using a dual-lumen balloon microcatheter.

Motor evoked potential monitoring can evaluate ischemic tolerance to carotid artery occlusion during surgery.

Balloon test occlusion (BTO) is a useful examination for evaluating ischemic tolerance to internal carotid artery (ICA) occlusion. The aim of this study was to investigate the relationships between intraoperative motor evoked potential (MEP) monitoring and the results of preoperative BTO. Between 2013 and 2017, 32 patients undergoing surgery under general anesthesia with intraoperative MEP monitoring, in whom preoperative BTO was performed, were identified. A receiver operator characteristic (ROC) analysis was performed to determine the appropriate cutoff value of MEP amplitude for BTO-positive. Furthermore, the accuracy of MEP monitoring for BTO-positive was compared with electroencephalogram (EEG) and somatosensory evoked potential (SEP) monitoring. Four of 32 (12.5%) patients were BTO-positive. The cutoff value of MEP amplitude for BTO-positive was a > 80% reduction from the baseline level, which showed sensitivity of 100% and specificity of 100%. Thus, the sensitivity and specificity for BTO-positive were significantly higher for MEP than for EEG (100% and 72.0%, p = 0.02) in 28 patients, but they were not significantly different compared with SEP (33.3% and 100%, p = 0.48) in 21 patients. MEP monitoring might be one of the alternatives for evaluating ischemic tolerance to ICA occlusion during surgery. The cutoff value of MEP amplitude was a > 80% reduction.

The Rate of Symptomatic Ischemic Events after Passing Balloon Test Occlusion of the Major Intracranial Arteries: Meta-Analysis.

BACKGROUND: Balloon test occlusion is a widely used method for predicting tolerance of vessel occlusion in the treatment of aneurysms, fistulae, and head and neck neoplasms. However, the false-negative rate is variably reported due in part to the diversity of perfusion monitoring methods. OBJECTIVE: To evaluate the rate of symptomatic ischemic events after a negative balloon test occlusion and determine whether perfusion monitoring methods contribute to differences in these rates. METHODS: PubMed was systematically searched for studies between 1990 and 2020 that reported rates of ischemic outcomes of parental vessel occlusion in patients who passed balloon test occlusion. A generalized linear mixed model meta-analysis was performed. Results were expressed as the rate of symptomatic ischemic events after parental vessel occlusion without vessel bypass in patients who passed balloon test occlusion. RESULTS: Thirty-two studies met the inclusion criteria. The overall pooled rate of ischemic events after passing balloon test occlusion was 3.7% (95% confidence interval [CI]: 1.7-7.8). This rate was 3.8% (95% CI: 1.1-12.8) when monitored with angiography, 2.2% (95% CI: 0.4-10.2) when monitored by a form of computed tomography, and 5.3% (95% CI: 1.2-20.4) when monitored by 2 or more methods of perfusion assessment. The complication rate of balloon test occlusion was 0.8% (95% CI: 0.2-2.7). CONCLUSIONS: Balloon test occlusion results in a low rate of subsequent ischemic events, without conclusive evidence of variation between methods of perfusion assessment. The choice of method should focus on reduction of complication risk, experience of the interventional team, and avoidance of prolonged test occlusion times.

Ischemic Tolerance Evaluated by Computed Tomography Perfusion during Balloon Test Occlusion.

OBJECTIVES: Balloon test occlusion (BTO) is performed to evaluate ischemic tolerance for large and giant cerebral aneurysms and head and neck tumors that may require parent artery occlusion. However, ischemic tolerance for the temporary test occlusion does not always guarantee a tolerance for permanent occlusion. In this study, we evaluated the utility of computed tomography (CT) perfusion during BTO to quantify ischemic tolerance for detecting delayed ischemic stroke. MATERIALS AND METHODS: Forty-one patients who underwent BTO for the internal carotid artery were included. The correlations between the parameters of CT perfusion and collateral angiographic appearance or stump pressure during BTO were evaluated. The cerebral blood flow (CBF), cerebral blood volume, mean transit time (MTT), and time to peak (TTP) were obtained through CT perfusion, and the asymmetry ratios were determined. Collateral angiographic appearances were categorized into 5 grades (0-4). RESULTS: The collateral angiographic appearance showed moderate correlations with CBF, MTT, and TTP that was significant. Of these, the absolute value of the correlation coefficient was the highest for MTT. MTT also showed a moderate correlation with stump pressure. CBF and MTT were significantly different between the poor collateral group (grades 2 and 3) and the good collateral group (grade 4). Based on the MTT, the good collateral group was identified with high sensitivity (75.0%) and specificity (81.2%). CONCLUSIONS: In BTO, the MTT obtained through CT perfusion showed a correlation with collateral angiographic appearance and stump pressure. Thus, the MTT might be useful to quantify ischemic tolerance for detecting delayed ischemic stroke.

Evaluation of Balloon Test Occlusion Before Therapeutic Carotid Artery Occlusion: Flat Detector Computed Tomography Cerebral Blood Volume Imaging versus Single-Photon Emission Computed Tomography.

OBJECTIVE: We aimed to compare flat detector computed tomography cerebral blood volume (FD-CBV) imaging to single-photon emission computed tomography (SPECT) as an adjunctive technique during balloon test occlusion (BTO) in patients with intracranial aneurysms or tumors. METHODS: Twelve patients who underwent SPECT (99mTc-ethyl cysteinate dimer) and FD-CBV imaging during BTO were enrolled. Color-coded cerebral blood flow (CBF) images and color-coded FD-CBV images were generated and visually inspected whether there were asymmetries between the ipsilateral and contralateral cerebral hemispheres. Region of interest measurements were performed on the color-coded images at the same locations for both modalities. The mean interhemispheric region of interest ratios were calculated, and the ratio between these were estimated using linear regression models. RESULTS: Ten patients had no symptoms during BTO. Two patients developed subtle but inconclusive neurologic changes approximately 10 minutes after balloon inflation; their images showed asymmetric color-coded images with decreased CBF and FD-CBV in the ipsilateral hemisphere. The mean interhemispheric ratio of CBF was significantly smaller in patients with subtle changes than in those without (0.84 vs. 0.98; P < 0.001). Similarly, the mean interhemispheric ratio of FD-CBV was significantly smaller in patients with subtle changes than in those without (0.88 vs. 1.06; P = 0.01). No patient showed increased CBF or FD-CBV in the ipsilateral hemisphere. CONCLUSIONS: The patients with decreased CBF on SPECT also showed decreased FD-CBV in the ipsilateral hemisphere. FD-CBV imaging may be useful as an adjunctive technique for BTO before potential therapeutic carotid artery occlusion.