Intraoperative evaluation of local cerebral hemodynamic change by indocyanine green videoangiography: prediction of incidence and duration of postoperative transient neurological events in patients with moyamoya disease

Intraoperative evaluation of local cerebral hemodynamic change by laser speckle contrast imaging for predicting postoperative cerebral hyperperfusion during STA-MCA bypass in adult patients with moyamoya disease

Cerebral hyperperfusion (CHP) occurred frequently after direct superficial temporal artery-middle cerebral artery (STA-MCA) bypass surgery for moyamoya disease (MMD). We analyzed cortical microvascular density (CMD) and the change of cerebral blood flow (LΔCBF) using intraoperative laser speckle contrast imaging (LSCI) on 130 hemispheres of 95 consecutive adult patients with MMD. The demographic characteristics, cortical hemodynamic sources, bypass methods, intraoperative blood flow data, and relative CBF changes on single-photon emission computed tomography (SPECT) examination (SΔrCBF) were compared between the groups with and without CHP. The median values for CMD, LΔCBF, and SΔrCBF were significantly higher in the CHP group than in the non-CHP group (CMD 0.240 vs 0.206, P = 0.004; LΔCBF 2.285 vs 1.870, P < 0.001; SΔCBF 1.535 vs 1.260, P < 0.001). Multivariate analysis revealed that hemodynamic sources of recipient parasylvian cortical arteries from MCA (M-PSCAs), end-to-side (E-S) bypass method, CMD ≥ 0.217, and LΔCBF ≥ 1.985 were the risk factors for CHP. Intraoperative LSCI was useful for evaluating hemodynamics and predicting CHP in patients with MMD.

Inhalational Anesthesia Reduced Transient Neurological Events After Revascularization Surgery for Moyamoya Disease

BACKGROUND AND OBJECTIVES

The choice between inhalational and total intravenous anesthesia (TIVA) in revascularization surgery for Moyamoya disease (MMD) remains a topic of debate. Anesthesia methods have changed with the advent of new anesthetics. This study investigated whether modern anesthesia methods affected the development of neurological symptoms after revascularization surgery for MMD.

METHODS

This single-center retrospective study included 63 adult patients (82 hemispheres) with MMD treated with direct and indirect bypass surgeries at our hospital between 2013 and 2022. Patients were divided into inhalational anesthesia (IA) and TIVA groups based on the anesthesia maintenance method. Baseline patient characteristics; postoperative neurological symptoms, including hyperperfusion syndrome, cerebral infarction, and transient neurological events (TNEs); and cortical hyperintensity belt (CHB) sign scores (5-point scale from 0 to 4) on postoperative magnetic resonance imaging were compared between the two groups. The operation methods, anesthetics, and intraoperative hemodynamic and ventilatory parameters were compared between patients with and without TNEs.

RESULTS

The IA and TIVA groups comprised 39 and 43 hemispheres, respectively. The frequency of postoperative hyperperfusion syndrome and cerebral infarction did not differ between the groups, but the number of TNEs in the IA group (5/39; 13%) was significantly lower than that in the TIVA group (16/43; 37%). Multivariate logistic regression analysis revealed that TNEs were associated with TIVA (odds ratio, 3.91; 95% CI, 1.24-12.35; P = .02). The median [IQR] postoperative CHB sign score in the IA group (2 [1-3]) was significantly lower than that in the TIVA group (4 [3-4]).

CONCLUSION

The IA group had fewer postoperative TNEs and lower CHB sign scores than the TIVA group. Although further studies are needed, this study provides insights into the prevention of TNEs with IA and reconsideration of the optimal anesthesia for MMD.

The value of indocyanine green-FLOW800 in microvasculature for predicting cerebral hyperperfusion syndrome in moyamoya disease patients

Among the notable complications of direct hemodynamic reconstruction for moyamoya disease (MMD) is cerebral hyperperfusion syndrome (CHS). In this study, we evaluated hemodynamic changes in small regional microvasculature (SRMV) around the anastomosis site by using indocyanine green (ICG)-FLOW800 video angiography and verified that it better predicted the onset of CHS. Intraoperative ICG-FLOW800 analysis was performed on 31 patients (36 cerebral hemispheres) with MMD who underwent superficial temporal artery-middle cerebral artery (MCA) bypass grafting at our institution. The regions of interest were established in the SRMV and thicker MCA around the anastomosis. Calculations were made for half-peak to time (TTP1/2), cerebral blood volume (CBV), and cerebral blood flow (CBF). According to the presence or absence of CHS after surgery, CHS and non-CHS groups of patients were separated. The results showed that ΔCBV and ΔCBF were substantially greater in SRMV than in MCA (p < 0.001). Compared with the non-CHS group, ΔCBF and ΔCBV of SRMV and MCA were considerably greater in the CHS group (p < 0.001). ΔCBF and ΔCBV on the ROC curve for both SRMV and MCA had high sensitivity and specificity (SRMV: ΔCBF, AUC = 0.8586; ΔCBV, AUC = 0.8158. MCA: ΔCBF, AUC = 0.7993; ΔCBV, AUC = 0.8684). ICG-FLOW800 video angiography verified the differential hemodynamic changes in the peri-anastomotic MCA and SRMV before and after bypass surgery in patients with MMD.

The Recipient Vessel Hemodynamic Features Affect the Occurrence of Cerebral Edema in Moyamoya Disease After Surgical Revascularization: A Single-Center Retrospective Study

Objective

In moyamoya disease (MMD) with direct or combined revascularization, the initially hemodynamic recipient features are likely one of the main causes of acute hemodynamic disruption. Previous studies have explored the relationship between recipient diameter or flow velocity and postoperative complications, but there are still no optimal selection criteria with multiple potential recipient vessels. Cerebral edema is one of the most common radiological manifestations in the acute postoperative period. This study assessed the hemodynamic characteristics of cortex vessels related to postoperative cerebral edema.

Methods

All patients who had undergone direct or combined revascularization with preoperative digital subtraction angiography (DSA) between 2019 and 2021 were eligible for inclusion in this study. The application of DSA was performed and regular radiological examinations were employed after surgery. DSA was analyzed with the hemodynamic features within chosen recipient vessels. Cerebral edema was identified as a low-density image on CT or high signaling in the MRI T2 phase. The recipient hemodynamic characteristics and demographic presentation, as well as clinical data, were retrospectively analyzed in this study.

Results

A total of 103 patients underwent direct or combined revascularization with preoperative DSA. The mean age of this enrolled cohort was 44.31 ± 10.386 years, in which bilaterally involved MMD accounted for the main part. The preliminary correlation analysis found preoperative disease period (p = 0.078), recipients observed in angiography (p = 0.002), and surgery on the left (p = 0.097) may be associated with cerebral edema. The following regression analysis confirmed low occurrence of cerebral edema was accompanied by recipients observed in angiography (p = 0.003). After subdividing by flow direction and hemodynamic sources, the incidence rate of anterograde direction, anterior sources, and posterior sources were significantly lower than undetected recipients.

Conclusions

Cerebral edema is a common radiological manifestation in MMDs after surgery. In this study, the observation in angiography reliably identifies a variety of physiological or pathological recipient detection, flow direction, and hemodynamic sources in patients with MMD after revascularization, which indicates the selection strategy of potential recipients and highlights the importance of recipient observability in DSA. Meanwhile, vascular conditions determined by recipient hemodynamics meditate the occurrence of postoperative cerebral edema.

Strategic tunnelling of superficial temporal artery during bypass surgery for moyamoya disease

BACKGROUND

The superficial temporal artery to middle cerebral artery bypass remains the favoured direct technique of cerebral revascularization in moyamoya angiopathy. We describe a novel technique of tunnelling the superficial temporal artery through the temporalis muscle.

METHODS

The temporalis muscle is raised as a flap off the temporal bone. A triangular window is created on the temporalis fascia, and a tunnel is created for the superficial temporal artery to pass through the muscle belly.

CONCLUSION

This innovative technique allows passage of the superficial temporal artery to the brain without kink or compression ensuring good bypass function and improves long-term patency.

Risk Factors for Cerebral Infarction Early After Revascularization in Children Younger than 5 Years with Moyamoya Disease

OBJECTIVE

Cerebral revascularization is necessary for pediatric patients younger than 5 years with moyamoya disease (MMD). However, they have a high risk of developing cerebral infarction early after surgery. This study aimed to analyze the risk factors for developing cerebral infarction among these patients.

METHODS

The charts of 21 consecutive patients with MMD (39 surgeries) younger than 5 years who had undergone revascularization at our hospital were retrospectively analyzed. Because cerebral infarction occurring within 1 month after surgery was the primary end point, other clinical information was evaluated, including each surgical procedure. Multivariate analysis of the risk factors for postoperative cerebral infarction was performed.

RESULTS

Cerebral infarction occurred after 7 of 39 surgeries (17.9%). Of the 39 surgeries, 23 (59%) included direct and indirect combined revascularization. The incidence of cerebral infarction did not differ significantly between the combined (21.7%) and indirect (12.5%) groups (P = 0.46). Logistic regression showed no association between the revascularization procedure and the occurrence of cerebral infarction after surgery (P = 0.3). However, younger age at surgery was correlated with a higher risk of developing cerebral infarction in the early postoperative period (P = 0.05).

CONCLUSIONS

No differences were found in the risk of developing cerebral infarction early after surgery as a result of surgical procedures. However, younger patients had higher postoperative risk. Further multicenter research should examine this issue for young pediatric patients with moyamoya at high risk of developing cerebral infarction.

Changes in cerebral blood flow in the postoperative chronic phase after combined cerebral revascularization for moyamoya disease with ischaemic onset

The purpose of this study was to examine the effects of combined revascularization for ischaemic-onset moyamoya disease (MMD) on cerebral haemodynamics by comparing cerebral blood flow (CBF) during the postoperative chronic phase with preoperative CBF. A retrospective cohort of 24 MMD patients (representing 31 surgeries) who received single photon emission computed tomography (SPECT) before and more than 6 months after surgery was investigated. The CBF value of each vascular territory was extracted from SPECT data, and the value relative to the ipsilateral cerebellar value (relative CBF, or RCBF) was calculated. The correlation between the revascularization effect and the proportional change in RCBF before and after surgery (calculated as post-RCBF/pre-RCBF ("post/pre-RCBF")) was analysed. Furthermore, the relationships between changes in neurological symptoms and post/pre-RCBF were investigated. Preoperative and postoperative mean RCBF values were 0.92 ± 0.15 and 0.96 ± 0.13 (p = 0.619) in the anterior cerebral artery territory, 0.99 ± 0.17 and 1.01 ± 0.17 (p = 0.598) in the middle cerebral artery territory and 1.15 ± 0.22 and 1.14 ± 0.19 (p = 0.062) in the posterior cerebral artery territory, respectively. No significant correlation was found between the revascularization score and post/pre-RCBF. The revascularization score and post/pre-RCBF were not significant predictors of worsening neurological symptoms postoperatively. No significant change in RCBF was observed in any vascular territory in the chronic phase after revascularization. Combined revascularization may assist in the redirection of blood flow from the internal to the external carotid system and contribute to CBF maintenance.

Challenging direct bypass surgery for very young children with moyamoya disease: technical notes

Cerebral revascularization for moyamoya disease (MMD) is an effective treatment for improving cerebral ischaemia and preventing rebleeding. Although direct bypass surgery is commonly performed on older children and adults, it is challenging in very young children due to the high difficulty level of the procedure. The subjects were MMD patients under 3 years of age on whom surgery was performed by a single surgeon (Y.A.). Preoperative clinical findings, information related to direct bypass surgery, bypass patency, and the incidence of postoperative stroke were investigated. Combined revascularization, including direct bypass surgery, was performed on 3 MMD patients (3 sides) under 3 years of age. The average diameter of the grafts used in direct bypass was 0.8 mm. The average recipient diameter was 0.8 ± 0.17 (range 0.6-1) mm. In all cases, the anastomotic procedure was completed using 11-0 monofilament nylon thread, and patency was confirmed. Direct bypass for MMD patients under 3 years old is technically challenging. However, despite the anatomical differences between very young children and elderly individuals, direct bypass surgery could certainly be completed. In addition, a rapid recovery from cerebral blood flow insufficiency could yield a promising neurological outcome.

＜Editors' Choice＞ Indocyanine green emission timing of the recipient artery in revascularization surgery for moyamoya disease

In superficial temporal artery to middle cerebral artery anastomosis with indirect revascularization for patients with moyamoya disease, the optimal method for selecting the most appropriate cortical artery for the recipient in anastomosis has not been established. We investigated the relationship between the fluorescence emission timing of the recipient artery in the preanastomosis indocyanine green videoangiography and operative outcomes. This retrospective study included 51 surgical revascularization procedures for 39 moyamoya disease patients. The enrolled surgical procedures were classified into three groups based on the fluorescence emission timing of the recipient artery in preanastomosis indocyanine green videoangiography: the EARLIEST, the INTERMEDIATE, and the LATEST. Clinical characteristics and operative outcomes were also collected. The occurrence of white thrombus at the anastomosis site and symptomatic hyperperfusion showed significant differences between the groups classified by the fluorescence emission timing of the recipient artery in preanastomosis indocyanine green videoangiography (white thrombus, p = 0.001; symptomatic hyperperfusion, p = 0.026). The development of white thrombi was significantly higher in the LATEST group, and all symptomatic hyperperfusion was observed in the EARLIEST group. These results indicated that the LATEST group had a significantly higher risk for developing white thrombus, and the EARLIEST group was prone to occur symptomatic hyperperfusion. Selecting the recipient artery based on evaluating the fluorescence emission timing in preanastomosis indocyanine green videoangiography may be useful in reducing perioperative complications.

Imaging methods for surgical revascularization in patients with moyamoya disease: an updated review

Neuroimaging is crucial in moyamoya disease (MMD) for neurosurgeons, during pre-surgical planning and intraoperative navigation not only to maximize the success rate of surgery, but also to minimize postsurgical neurological deficits in patients. This is a review of recent literatures which updates the clinical use of imaging methods in the morphological and hemodynamic assessment of surgical revascularization in patients with MMD. We aimed to assist surgeons in assessing the status of moyamoya vessels, selecting bypass arteries, and monitoring postoperative cerebral perfusion through the latest imaging technology.

Intraoperative transit-time ultrasonography combined with FLOW800 predicts the occurrence of cerebral hyperperfusion syndrome after direct revascularization of Moyamoya disease: a preliminary study

BACKGROUND

Cerebral hyperperfusion syndrome (CHS) is a common complication after direct bypass surgery in patients with Moyamoya disease (MMD). Since preventive measures may be inadequate, we assessed whether the blood flow difference between the superficial temporal artery (STA) and recipient vessels (△BF) and the direct perfusion range (DPR) are related to CHS.

METHODS

We measured blood flow in the STA and recipient blood vessels before bypass surgery by transit-time probe to calculate △BF. Perfusion changes around the anastomosis before and after bypass were analyzed with FLOW800 to obtain DPR. Multiple factors, such as △BF, DPR, and postoperative CHS, were analyzed using binary logistic regression.

RESULTS

Forty-one patients with MMD who underwent direct bypass surgery were included in the study. Postoperative CHS symptoms occurred in 13/41 patients. △BF and DPR significantly differed between the CHS and non-CHS groups. The optimal receiver operating characteristic (ROC) curve cut-off value was 31.4 ml/min for ΔBF, and the area under the ROC curve (AUC) was 0.695 (sensitivity 0.846, specificity 0.500). The optimal cut-off value was 3.5 cm for DPR, and the AUC was 0.702 (sensitivity 0.615, specificity 0.750).

CONCLUSION

Postoperative CHS is caused by multiple factors. △BF is a risk factor for CHS while DPR is a protective factor against CHS.

Postoperative stroke and neurological outcomes in the early phase after revascularization surgeries for moyamoya disease: an age-stratified comparative analysis

Stroke and neurological outcomes in the early phase following revascularization for moyamoya disease (MMD) may depend on the patient's age. In this study, an age-stratified comparative analysis was performed to clarify this issue. We reviewed 105 MMD patients who underwent 179 revascularization surgeries. The demographic characteristics were collected in four age groups (≤ 5 and 6-17 years for pediatric patients and 18-49 and ≥ 50 years for adults). Additionally, we assessed the incidence of subsequent stroke and deterioration of modified Rankin Scale (mRS) score. Then, we evaluated predictors of postoperative stroke and mRS deterioration using logistic regression. The mean patient age was 26.2 ± 18.5 years. No significant difference in the incidence of postoperative stroke was observed between age groups; however, the incidence tended to be increased among patients aged ≤ 5 years (17.9%) and patients aged ≥ 50 years (16.7%). Deterioration of mRS scores was significantly associated with ages ≤ 5 years (17.9%) and ≥ 50 years (11.1%). Logistic regression showed that posterior cerebral artery involvement (odds ratio [OR], 4.6) and postoperative transient neurological events (TNEs) (OR, 5.93) were risk factors for postoperative stroke. Age ≤ 5 years (OR, 9.73), postoperative TNEs (OR, 7.38), and postoperative stroke (OR, 49) were identified as predictors of unfavorable neurological outcomes. The novel feature of this comparative analysis by age group is that membership in the early-childhood MMD patient group (under 5 years old) was an independent risk factor for unfavorable short-term neurological outcomes and was mainly associated with the incidence of postoperative severe cerebral infarction.

Intraoperative local hemodynamic quantitative analysis of direct revascularization in patients with moyamoya disease

Direct bypass surgery improves blood flow in patients with moyamoya disease (MMD) as well as causes local flow relocation and disturbance. This study aimed to describe the characteristics and changes of quantitative blood flow in MMD patients. Sixty-four consecutive MMD patients (67 hemispheres) who underwent STA-MCA anastomosis between August 2013 and September 2017 were included in this study. Intraoperative blood flow of superficial temporal artery and middle cerebral artery was measured with a noninvasive, ultrasound flowprobe, before and after the bypass. All data were collected prospectively. Before the bypass, 67 hemispheres were measured and 45 hemispheres acquired post-bypass measurements. Thirty-three (49.3%) had anterograde flow and 34 (50.7%) had retrograde. Retrograde blood flow was significantly higher than anterograde blood flow in MCA-M4 section (3.71 ± 2.78 ml/min vs 2.39 ± 1.71 ml/min, P = 0.023). Thirty-eight (56.7%) patients had local cerebrovascular reactivity, whereas 29 (43.3%) lost it. After bypass, blood flow was changed into three patterns: anterograde flow (1, 2.2%), retrograde flow (3, 6.7%), and bi-direction flow (41, 91.1%). Flow of M4 was significantly improved in both proximal (13.64 ± 9.16 vs 3.28 ± 2.57, P < 0.001) and distal (7.17 ± 7.21 vs 3.28 ± 2.57, P = 0.002) sides to the bypass. Postoperative infarctions occurred in 4 (8.9%) patients. All postoperative infarctions (n = 4) happened in those patients who did not have change of flow direction in M4 section distal to the bypass (P = 0.040). Direct bypass surgery improves local blood flow after bypass surgery in both sides of the anastomosis. Flow direction was usually changed after the surgery into a bi-direction pattern: anterograde flow in M4 distal to the bypass, and retrograde flow in M4 proximal to the bypass. Proximal side acquired around 5.4 times of flow than the distal side. Patients with change of flow direction in distal M4 were related with lower risks of postoperative infarctions.

Evaluation of Hemodynamic Change by Indocyanine Green-FLOW 800 Videoangiography Mapping: Prediction of Hyperperfusion Syndrome in Patients with Moyamoya Disease

Objective

Hyperperfusion syndrome (HPS) after bypass surgery for moyamoya disease (MMD) mainly results from redistribution of blood flow, which leads to poor outcomes, while effective methods to predict HPS are still lacking. Indocyanine green (ICG) videoangiography can assess regional cerebral blood flow changes semiquantitatively with the application of FLOW 800 software. The purpose of this study was to investigate whether the intraoperative evaluation of local hemodynamic changes around anastomotic sites using FLOW 800 videoangiography mapping can predict the incidence of HPS and clinical outcomes.

Methods

Of the patients who were diagnosed with MMD in our hospital between August 2018 and December 2019, who underwent superficial temporal artery-middle cerebral artery bypass surgeries, we investigated 65 hemispheres (in 62 patients) in which intraoperative ICG analysis was performed using FLOW 800 (Zeiss Meditec, Oberkochen, Germany) to evaluate the local cerebral hemodynamics before and after anastomosis. Regions of interest were set at more than 2 points on the brain surface according to the location and situation of recipient arteries in the surgical area. Peak cerebral blood volume (CBV), regional cerebral blood flow (CBF), and time to peak (TTP) were calculated from the selected points. As the data were available intraoperatively, anastomoses were performed in a suitable area. According to the occurrence of HPS, patients were divided into the asymptomatic and symptomatic groups, from which hemodynamic parameters were compared. Furthermore, ROC analysis was performed to determine the diagnostic accuracy of change rates in CBV, CBF, and TTP (i.e., ΔCBV, ΔCBF, and ΔTTP) for predicting HPS.

Results

Data from the 62 patients were analyzed, and all patients were closely assessed during hospitalization after the procedures. The values of ΔCBV and ΔCBF were significantly higher in the symptomatic group (p < 0.01), while ΔTTP is slightly lower in the symptomatic group with no statistical differences (p = 0.72). Hemodynamic parameters including ΔCBV and ΔCBF, calculated by FLOW 800, had high sensitivity and specificity according to the ROC curve (ΔCBV: AUC = 0.743, 95% CI, 0.605-0.881, p = 0.002; ΔCBF: AUC = 0.852, 95% CI, 0.750-0.954, p < 0.01), which could be used as predictors for HPS.

Conclusions

Intraoperative ICG-FLOW 800 videoangiography mapping is a safe method which can reflect hemodynamic characteristics in the surgical area for MMD, the findings of which correlate with the occurrence of HPS. Parameters including ΔCBV and ΔCBF are proven to be efficient in the prediction of HPS.

Applications of Microscope-Integrated Indocyanine Green Videoangiography in Cerebral Revascularization Procedures

Indocyanine green videoangiography (ICG-VA) is a near-infrared range fluorescent marker used for intraoperative real-time assessment of flow in cerebrovascular surgery. Given its high spatial and temporal resolution, ICG-VA has been widely established as a useful technique to perform a qualitative analysis of the graft patency during revascularization procedures. In addition, this fluorescent modality can also provide valuable qualitative and quantitative information regarding the cerebral blood flow within the bypass graft and in the territories supplied. Digital subtraction angiography (DSA) is considered to be the gold standard diagnostic modality for postoperative bypass graft patency assessment. However, this technique is time and labor intensive and an expensive interventional procedure. In contrast, ICG-VA can be performed intraoperatively with no significant addition to the total operative time and, when used correctly, can accurately show acute occlusion. Such time-sensitive ischemic injury detection is critical for flow reestablishment through direct surgical management. In addition, ICG has an excellent safety profile, with few adverse events reported in the literature. This review outlines the chemical behavior, technical aspects, and clinical implications of this tool as an intraoperative adjunct in revascularization procedures.