Protective STA-MCA bypass to prevent brain ischemia during high-flow bypass surgery: case series of 10 patients

Virtual cut flow, an innovative noninvasive 4D ASL MRI biomarker of EIC bypass patency

Extracranial-intracranial (EIC) bypasses are used to treat Moya-Moya syndrome and complex aneurysms. Evaluating bypass patency is vital. Current methods include intraoperative techniques like indocyanine angiography, micro-doppler probes, and postoperative non-invasive imaging. However, adjudicating the frequent discordant imaging results is done via conventional digital subtraction angiography (DSA) despite its associated risks. Our study aims to quantitatively evaluate bypass patency by introducing a novel biomarker, the virtual cut-flow index (VCFI) derived from 4D-PACK MRI imaging. We prospectively reviewed consecutive adult patients who underwent bypass surgery at our institution between January and October 2023. MR angiography was performed, employing 4D-PACK (four-dimensional pseudo-continuous arterial spin labeling (4D-pCASL)-based angiography using CENTRA-keyhole and view sharing) imaging. We measured arterial signal intensity using regions of interest (ROIs) placed on the superficial temporal artery (STA) and a branch of the middle cerebral artery (MCA) post-bypass. We modeled signal evolution using linear regression and extracted slope α coefficients and then calculated the virtual cut-flow index (VCFI) using the equation VCFI = αMCA/αSTA. We included 18 patients corresponding to 19 bypasses. The median VCI was significantly higher in patients with a patent bypass compared to those with an occluded bypass (87.33 vs. 19.87%; p < 0.05). The median αMCA coefficient was significantly higher in patients with a patent bypass compared to those with an occluded bypass (69.21 vs. 11.34; p < 0.05). The median αSTA coefficient was significantly higher in patients with a patent bypass compared to those with an occluded bypass (102.74 vs. 44.74; p < 0.05). We introduced a novel noninvasive biomarker, the virtual cut-flow index, as a new means to assess bypass patency. While DSA remains the gold standard, VCFI offers a promising avenue for quantitative evaluation, potentially enhancing postoperative monitoring and influencing surgical planning.

Long-term results and neuropathy of internal carotid artery aneurysms treated with high-flow bypass using saphenous vein graft and parent artery occlusion

OBJECTIVES

Giant internal carotid artery aneurysms require treatment owing to the risk of rupture, cranial nerve palsy in the cavernous sinus, and optic nerve symptoms. Among treatment options for internal carotid artery aneurysms, we compared the results of flow diverter stent with those of high-flow bypass.

MATERIALS AND METHODS

A total of 45 consecutive patients with large or giant internal carotid artery aneurysms underwent high-flow bypass using saphenous vein graft and double assist superficial temporal artery-middle cerebral artery bypass and proximal ligation of the internal carotid artery at the neck.

RESULTS

The high-flow bypass patency rate was 96 %. Among the target aneurysms, 78 % and 96 % thrombosed within one and three years postoperatively, respectively. Neurological symptoms associated with aneurysms improved in 69 % of patients. The complication rate was 4 %. The thrombosis rate of aneurysms treated with high-flow bypass tended to be higher and faster than those treated with flow diverter stent.

CONCLUSIONS

Even in the era of flow diverter stenting, treatment with high-flow bypass should be considered for patients who have difficulty with flow diverter stent implantation or without thromboses. Therefore, the treatment of cerebral aneurysms with high-flow bypass requires high safety and efficacy.

Can Evoked Potential Changes during the Superficial Temporal Artery-Middle Cerebral Artery Bypass Surgery Predict Postoperative Improvement of Cerebral Perfusion and Functional Status?

BACKGROUND

We investigated evoked potential (EP) changes during superficial temporal artery to middle cerebral artery (STA-MCA) bypass surgery and their correlations with imaging and clinical findings postoperatively.

METHODS

This retrospective study included patients who underwent STA-MCA bypass surgery due to ischemic stroke with large artery occlusion (MB group). Patients who underwent unruptured MCA aneurysm clipping were enrolled in the control group (MC group). Median and tibial somatosensory evoked potentials (SSEP), and motor evoked potentials recorded from the abductor pollicis brevis (APB-MEP) and abductor hallucis (AH-MEP) were measured intraoperatively. Modified Rankin scale (mRS) and perfusion-weighted imaging (PWI) related variables, i.e., mean transit time (MTT) and time to peak (TTP), were assessed.

RESULTS

Δmedian SSEP, ΔAPB-MEP, and ΔAH-MEP were significantly higher in the MB group than in the MC group (p = 0.027, p = 0.006, and p = 0.015, respectively). APB-MEP and AH-MEP amplitudes were significantly increased at the final measurement (p = 0.010 and p < 0.001, respectively). The ΔTTP asymmetry index was moderately correlated with ΔAPB-MEP (r = 0.573, p = 0.005) and ΔAH-MEP (r = 0.617, p = 0.002). ΔAPB-MEP was moderately correlated with ΔMTT (r = 0.429, p = 0.047) and ΔmRS at 1 month (r = 0.514, p = 0.015).

CONCLUSIONS

MEP improvement during STA-MCA bypass surgery was partially correlated with PWI and mRS and could reflect the recovery in cerebral perfusion.

High-flow bypass using saphenous vein grafts with trapping of ruptured blood blister-like aneurysms of the internal carotid artery: patient series

BACKGROUND

Trapping an aneurysm after the establishment of an extracranial to intracranial high-flow bypass is considered the optimal surgical strategy for ruptured blood blister-like aneurysms (BBAs) of the internal carotid artery (ICA). For high-flow bypass surgeries, a radial artery graft is generally preferred over a saphenous vein graft (SVG). However, SVGs can be advantageous in acute-phase surgeries because of their greater length, easy manipulability, ability to act as high-flow conduits, and reduced risk of vasospasms. In this study, the authors presented five cases of ruptured BBAs treated with high-flow bypass using an SVG followed by BBA trapping, and they reported on surgical outcomes and operative nuances that may help avoid potential pitfalls.

OBSERVATIONS

After the surgeries, there were no ischemic or hemorrhagic complications, including symptomatic vasospasms. In three of the five cases, postoperative modified Rankin scale scores were between 0 and 2 at the 3-month follow-up. In one case, the SVG spontaneously occluded after surgery while the protective superficial temporal artery (STA) to middle cerebral artery (MCA) bypass became dominant, and the patient experienced no ischemic symptoms.

LESSONS

High-flow bypass using an SVG with a protective STA-MCA bypass followed by BBA trapping is a safe and effective treatment strategy.

Cerebral revascularization for the management of complex middle cerebral artery aneurysm: A case series

Complex middle cerebral artery (MCA) aneurysms, including aneurysms that are sizeable (large or giant), fusiform, wide-necked or calcified, remain a significant challenge during microsurgical clipping or endovascular coiling as treatment strategies. In the present study, a retrospective analysis of cases of this type of aneurysm treated between August 2012 and December 2019 was performed. From the hospital's database, a total of 13 patients (7 males and 6 females) with a mean age of 39.0 years (range, 13-65 years) were identified. The mean size of the aneurysms was 17.5 mm (range, 3.9-35.0 mm). A total of four patients (30.8%) had ruptured aneurysms and nine (69.2%) had unruptured aneurysms. All aneurysms were treated by proximal occlusion of the parent artery, trapping or excision combined with cerebral revascularization. The bypasses performed included 10 extracranial-intracranial bypasses and 3 intracranial-intracranial bypasses (1 end-to-end re-anastomosis, 1 interpositional graft and 1 end-to-side reimplantation). Postoperative angiography confirmed that the bypass patency was 92.3% and the clinical outcomes were indicated to be favorable, with a modified Rankin Scale score ≤2 in 12 out of 13 patients (92.3%) at the last follow-up. Taken together, the results of the present analysis suggested that treatment strategies for complex MCA aneurysms should depend on the status and characteristics of the aneurysm, including aneurysm size, location and morphology. For aneurysms that lack perforating arteries in the aneurysm dome, clip trapping or aneurysm excision with or without bypass are preferred as treatment strategies. When there are perforating arteries (particularly the lenticulostriate artery) arising from the aneurysm dome, however, the aneurysms should be treated with bypass followed by proximal occlusion of the parent artery or clip reconstruction.

Ruptured blood blister like aneurysm: does the best therapeutic option really exist?

Our study aimed to evaluate the outcome of patients with ruptured blood-blister like aneurysm (BBLA) in our institution by comparing microsurgical selective treatment to endovascular treatment using flow-diverter stent (FD). Our study included 18 consecutive patients treated for BBLA between 2004 and 2020. Until 2014, microsurgery was preferred in all patients with BBLA (n = 10). Significant postoperative morbi-mortality was recorded at this time and led us to change therapeutic strategy and to favor FD as first-line treatment in all patients (n = 8). Postprocedural complications and BBLA occlusion were recorded. High WFNS score (> 2) was noted in 6 patients of microsurgical group and in 2 of endovascular group. In microsurgical group, ischemic lesions were noted in 6 patients and led to death in 3 patients. Immediate BBLA occlusion was obtained in all patients. Favorable outcome after 3 months (mRS < 3) was recorded in 4 of the 7 survivors. In endovascular group, ischemic lesions were noted in 4 patients. One patient died from early postprocedural BBLA rebleeding. Scarpa hematoma was noted in 3 patients with surgical evacuation in 1. Persistent BBLA at 3 months was recorded in 4 patients without rebleeding, but further FD was required in 1 with growing BBLA. Favorable outcome was noted in 6 of the 7 survivors. Although, rate of morbi-mortality appear lower in patients treated with FD, neurological presentation was better and BBLA diagnosis remains questionable in this group. Moreover, persistent BBLA imaging with potential risk of rebleeding after FD deserves to be discussed.

The evaluation of intracranial bypass patency in neurosurgical practice

BACKGROUND

The patency of cranial bypasses must be carefully evaluated during and after the microsurgical procedure. Although, several imaging techniques are used to evaluate the patency of bypasses, their findings are sometimes difficult to interpret.

PURPOSE

The goal of this study was to assess the consistency of different diagnostic modalities for evaluating intracranial bypass patency.

PATIENTS AND METHOD

This prospective study included 19 consecutive patients treated with EC-IC or IC-IC bypass for MoyaMoya disease (MMD) or complex/giant aneurysms between June 2016 and June 2018. In the early postoperative period (<7 days), all patients had transcranial Doppler (TCD), CT angiography (CTA) and MRA to demonstrate patency of anastomoses and to confirm exclusion of the aneurysm. When findings of anastomosis patency differed between these techniques, conventional angiography was performed.

RESULTS

All anastomoses were patent on indocyanine green videoangiography at the end of microsurgical procedure. The results of noninvasive postoperative exams were consistent to demonstrate the patency of anastomoses in 13 patients. In 4 patients, a discrepancy in patency of anastomoses arose between TCD, CTA and MRI in the early postoperative period. In 2 other patients, the interpretation of bypass patency remained inconclusive before the decision to occlude the aneurysm. In these 6 patients, a significant edema was noted in 2 cases, a postoperative subdural hematoma in 1 case, a low flow in the anastomosis in 1 case and vasospasm in 2 cases. The anastomosis was patent on the conventional angiography in five patients.

CONCLUSION

Noninvasive imaging techniques provide useful data about the patency but their findings should be carefully interpreted due to local anatomical, physiological, and pathological factors. In case of discrepant findings, conventional angiography including supraselective catheterization of the donor vessel is suggested.

Incision Edge "Lifting Method" in Cerebral Bypass Surgery: A Novel Optional Technique for Narrow or Thin Recipient Arteries

BACKGROUND

Cerebral bypass surgery, such as the superficial temporal artery-middle cerebral artery bypass, is one of the essential procedures for cerebral revascularization. However, very narrow or thin blood vessels will increase the risk of anastomotic problems, such as occurs in Moyamoya disease. For such vessels, we have devised a "lifting method" in the recipient arteriotomy. In the present study, we have introduced this novel optional technique and evaluated its effects.

METHODS

The lifting method is a procedure of lifting the incision edge of a linear incision on the recipient vessel to widen the ostium. We attempted the lifting method in 23 consecutive patients (41 arteries) and, as a historical control, compared the results with those from the conventional method in 25 consecutive patients (37 arteries) for the previous 3 years. We compared patient age, years of surgical experience, recipient vessel diameter, anastomotic events, and final patency. As a subanalysis, the same evaluations were performed separately for patients with Moyamoya disease. Furthermore, the time required for the lifting procedure was measured retrospectively.

RESULTS

The incidence of anastomotic events with the conventional method was 13.5% overall and 19% in those with Moyamoya disease. No adverse events occurred with the lifting method (P < 0.05). No statistically significant differences were found for the other factors, including final patency between the 2 groups. The time required for the lifting procedure averaged 1 minute, 15 seconds.

CONCLUSIONS

Use of the lifting method widens and secures the ostium in a recipient vessel and greatly facilitates operability. We have found it to be a foolproof method enabling safe and reliable anastomosis even with narrow or thin vessels.