Radial Artery Grafts as Rescue Strategy for Patients with Moyamoya Disease for Whom Conventional Revascularization Failed

Hemodynamic Effects of Tortuosity and Stenosis in Superficial Temporal Artery-Middle Cerebral Artery Bypass for Moyamoya Disease

BACKGROUND

Superficial temporal artery (STA)-middle cerebral artery (MCA) bypass surgery has been widely adopted in treating moyamoya disease (MMD). Geometric variations including high tortuosity and stenosis exist in many cases, but the hemodynamic effects have not been comprehensively evaluated. We aim to evaluate the hemodynamic effects of bypass geometry variations based on patient-specific data.

METHODS

In total, 17 patients with MMD who underwent STA-MCA bypass surgery with highly tortuous bypass geometry were included. For each patient, the original 3-dimensional structure of STA-MCA bypass was reconstructed from clinical imaging data. The bypass structure was virtually improved by removing the tortuosity and stenosis. Computational fluid dynamics simulation was performed on both bypass structures under identical patient-specific condition. The simulated hemodynamic parameters of the bypass and its distal branches were compared between the original and virtually improved bypass geometries in all cases using paired t-test or Wilcoxon signed-rank test. The changes of hemodynamic parameters were compared between the cases with and without mild-to-moderate stenosis (44.0-70.3% in diameter) in the bypass using t-test or Mann-Whitney U test.

RESULTS

The virtual improvement of bypass geometry significantly increased the flow rate of the bypass and its distal branches (P < 0.05) and decreased the transcranial flow resistance (P < 0.05). The hemodynamic changes in cases with stenosis removal were significantly greater than those without stenosis (P < 0.05).

CONCLUSIONS

High tortuosity and stenosis can significantly change the hemodynamics of STA-MCA bypass, and the optimization of bypass geometry deserves further consideration.

Characterization of Global Research Trends and Prospects on Moyamoya Disease: Bibliometric Analysis

BACKGROUND

Moyamoya disease (MMD) is a rare cerebrovascular disease in neurology. This study investigates the literature related to MMD from its discovery to the present and identifies research levels, achievements, and trends.

METHODS

All publications on MMD from its discovery to present were downloaded from the Web of Science Core Collection on September 15, 2022 and bibliometric analyses were visualized by HistCite Pro, VOSviewer, Scimago Graphica, CiteSpace, and R language.

RESULTS

There were 3414 articles in 680 journals by 10,522 authors in 2441 institutions and 74 countries/regions worldwise are included in the analyses. Since the discovery of MMD, output of publications has shown an upward trend. Japan, the United States, China, and South Korea are 4 major countries in MMD. The United States has the strongest cooperation with other countries. China's Capital Medical University is the output-leading institution worldwide, followed by Seoul National University and Tohoku University. The 3 authors with the most published articles are Kiyohiro Houkin, Dong Zhang, and Satoshi Kuroda. World Neurosurgery, Neurosurgery, and Stroke are the most recognized journals for researchers. Hemorrhagic moyamoya disease, susceptibility gene, and arterial spin are the primary focus areas of MMD research. "Rnf213,""vascular disorder," and "progress" are the top keywords.

CONCLUSIONS

We analyzed publications of global scientific research on MMD systematically by bibliometric methods. This study can provide one of the most comprehensive and accurate analyses for MMD scholars worldwide.

Wide Arterial Sparing Encephalo-Duro-Synangiosis for Moyamoya: Surgical Technique and Outcomes

BACKGROUND

Moyamoya is managed by surgical revascularization, but no standardized method has yet been universally adopted.

OBJECTIVE

To describe a new indirect bypass technique for pediatric moyamoya, wide arterial sparing encephalo-duro-synangiosis (WASEDS), which provides a much wider area of revascularization with minimal compromise to the middle meningeal arterial tree compared with traditional procedures. Initially used as a salvage technique after failed encephalo-duro-arterio-synangiosis, its success later motivated its use as a first-line procedure.

METHODS

Clinical and radiographic records of patients who underwent WASEDS for moyamoya from 2009 to 2020 were reviewed. Brain perfusion relative cerebral blood volume on the side of the WASEDS procedure was calculated. Two-tailed paired t tests were performed to identify the statistically significant differences ( P ≤ .05).

RESULTS

WASEDS was successfully performed on 8 patients for a total of 14 cerebral hemispheres. Age ranged from 2 to 25 years. There were no mortalities. The average clinical and radiographic follow-up was 49.79 months (range 2-126 months), demonstrating improvement in neurological condition and no postoperative stroke and significant diminution or cessation of transient ischemic attacks in all patients. Relative cerebral blood volume increased 9.24% after the WASEDS procedure ( P = .012). There were no neurological complications. There were 2 pseudomeningoceles related to the extensive dural openings.

CONCLUSION

WASEDS is a safe and effective indirect revascularization technique for both primary and salvage techniques. It provides an extensive area of cortical revascularization with no compromise of the middle meningeal vasculature and subjective reports of early improvement in cognition and behavior. The main disadvantage is elevated risk of pseudomeningocele secondary to the large craniotomy.

"Recycling" a failed superficial temporal artery indirect bypass into a double barrel direct bypass in moyamoya disease

OBJECTIVES

Moyamoya disease is an idiopathic cerebrovascular disorder in which patients experience recurrent transient ischemic attacks, ischemic or hemorrhagic strokes, headaches, and seizures from progressive stenosis of the vessels of the anterior circulation. The mainstay of treatment in symptomatic patients is surgical revascularization. Here, we present the case of a moyamoya patient in which a failed encephaloduroarteriosynangiosis, after new strokes, is recycled and converted into a combined "double barrel" direct superficial temporal artery to middle cerebral artery bypass with included video.

CASE REPORT/RESULTS

We describe a 37-year-old woman with a history of hypertension, obstructive sleep apnea, celiac disease, and moyamoya disease complicated by multiple ischemic strokes who presented with progressive dysarthria, dysphagia, and new left-sided ischemic infarcts. The patient had previously undergone right-sided direct bypass and left-sided encephaloduroarteriosynangiosis in the setting of multiple ischemic strokes. After more strokes, the patient underwent a left-sided frontotemporoparietal craniotomy for conversion of the failed indirect bypass into a "double barrel" direct bypass.

CONCLUSIONS

The literature is divided over which revascularization procedure should be preferred. Irrespectively, most failed bypass grafts are repaired via direct bypasses, to good effect. We highlight a case in which a failed indirect bypass is directly incorporated into a combined direct bypass with resulting restoration of blood flow. In the case of a failed indirect bypass in an adult patient with moyamoya disease, this method provides the operator with an additional option for restoration of perfusion, especially in patients without other viable vessels available for anastomosis.

The Genetic Basis of Moyamoya Disease

Moyamoya disease (MMD) is a rare cerebrovascular disease characterized by progressive spontaneous bilateral occlusion of the intracranial internal cerebral arteries (ICA) and their major branches with compensatory capillary collaterals resembling a “puff of smoke” (Japanese: Moyamoya) on cerebral angiography. These pathological alterations of the vessels are called Moyamoya arteriopathy or vasculopathy and a further distinction is made between primary and secondary MMD. Clinical presentation depends on age and population, with hemorrhage and ischemic infarcts in particular leading to severe neurological dysfunction or even death. Although the diagnostic suspicion can be posed by MRA or CTA, cerebral angiography is mandatory for diagnostic confirmation. Since no therapy to limit the stenotic lesions or the development of a collateral network is available, the only treatment established so far is surgical revascularization. The pathophysiology still remains unknown. Due to the early age of onset, familial cases and the variable incidence rate between different ethnic groups, the focus was put on genetic aspects early on. Several genetic risk loci as well as individual risk genes have been reported; however, few of them could be replicated in independent series. Linkage studies revealed linkage to the 17q25 locus. Multiple studies on the association of SNPs and MMD have been conducted, mainly focussing on the endothelium, smooth muscle cells, cytokines and growth factors. A variant of the RNF213 gene was shown to be strongly associated with MMD with a founder effect in the East Asian population. Although it is unknown how mutations in the RNF213 gene, encoding for a ubiquitously expressed 591 kDa cytosolic protein, lead to clinical features of MMD, RNF213 has been confirmed as a susceptibility gene in several studies with a gene dosage-dependent clinical phenotype, allowing preventive screening and possibly the  development of new therapeutic approaches. This review focuses on the genetic basis of primary MMD only.

Surgical Management of Failed Revascularization in Moyamoya Vasculopathy

Objectives: Moyamoya vasculopathy (MMV) is a rare stenoocclusive cerebrovascular disease associated with increased risk of ischemic and hemorrhagic stroke, which can be treated using surgical revascularization techniques. Despite well-established neurosurgical procedures performed in experienced centers, bypass failure associated with neurological symptoms can occur. The current study therefore aims at characterizing the cases of bypass failure and repeat revascularization at a single center.

Methods: A single-center retrospective analysis of all patients treated with revascularization surgery for MMV between January 2007 and December 2019 was performed. Angiographic data, cerebral blood flow analysis [H₂O PET or single-photon emission CT (SPECT)], MRI, and clinical/operative data including follow-up assessments were reviewed.

Results: We identified 308 MMV patients with 405 surgically treated hemispheres. Of the 405 hemispheres treated, 15 patients (3.7%) underwent repeat revascularization (median age 38, time to repeat revascularization in 60% of patients was within 1 year of first surgery). The most common cause of repeat revascularization was a symptomatic bypass occlusion (80%). New ischemic lesions were found in 13% of patients prior to repeat revascularization. Persistence of reduced or progressive worsening of cerebrovascular reserve capacity (CVRC) compared with preoperative status was observed in 85% of repeat revascularization cases. Intermediate-flow bypass using a radial artery graft was most commonly used for repeat revascularization (60%) followed by re-superficial temporal artery to middle cerebral artery (re-STA-MCA) bypass (26%). High-flow bypass using a saphenous vein graft and using an occipital artery to MCA bypass was each used once. Following repeat revascularization, no new ischemic events were recorded.

Conclusion: Overall, repeat revascularization is needed only in a small percentage of the cases in MMV. A rescue surgery should be considered in those with neurological symptoms and decreased CVRC. Intermediate-flow bypass using a radial artery graft is a reliable technique for patients requiring repeat revascularization. Based on our institutional experience, we propose an algorithm for guiding the decision process in cases of bypass failure.

Vessel-selective 4D MRA based on ASL might potentially show better performance than 3D TOF MRA for treatment evaluation in patients with intra-extracranial bypass surgery: a prospective study

OBJECTIVES

To compare bypass patency and intracranial collaterals from the external carotid artery (ECA) by four-dimensional MR angiography (MRA) based on super-selective pseudo-continuous arterial spin labeling (pCASL) combined with the keyhole and view-sharing techniques (4D-sPACK) versus three-dimensional time-of-flight (3D TOF) MRA in patients with extra-intracranial revascularization.

METHODS

The MR data of 45 patients administered bypass surgery were collected. The image quality of 4D-sPACK was evaluated using a 4-point grading system according to whether the diagnosis of intracranial collaterals was affected. Anastomosis patency and intracranial collateral visualization from ECA were assessed by two radiologists on 4D-sPACK and 3D TOF MRA, with digital subtraction angiography (DSA) findings as reference. Intracranial collateral assessment employed another 4-point grading system according to the number of vessels shown. Interobserver agreement was assessed with the weighted kappa statistic.

RESULTS

Fifty hemispheres in 43 patients were included. The image quality of 4D-sPACK was good in 47 (47/50, 94.0%) hemispheres. 4D-sPACK had a higher sensitivity than 3D TOF MRA (97.73% vs 79.55%) for visualizing anastomoses. There were significant differences between 4D-sPACK (scores, 3.22 ± 1.15) and 3D TOF MRA (scores, 1.80 ± 0.67) in the visualization of intracranial collaterals from ECA (p < 0.001). The interobserver agreement was substantial for intracranial collateral assessment (κ_4D-sPACK = 0.788; κ_{3D TOF MRA} = 0.800) and almost perfect for bypass patency (κ_4D-sPACK = 0.912; κ_{3D TOF MRA} = 0.816; κ_DSA = 0.811).

CONCLUSION

This pilot study shows that, 4D-sPACK has a better performance than 3D TOF MRA in treatment evaluation of patients after bypass surgery, and has high consistency with DSA.

KEY POINTS

• 4D-sPACK is a non-contrast-enhanced dynamic MRA method for the visualization of intracranial vessels. • 4D-sPACK has higher specificity for the diagnosis of anastomosis occlusion. • 4D-sPACK is better than 3D TOF MRA in the visualization of intracranial collaterals in patients after bypass surgery.

Strategy and effect of repeat bypass surgery for anterior/posterior circulation in refractory moyamoya disease

OBJECTIVE

In this study the authors aimed to describe clinical features, surgical techniques, and long-term outcomes of repeat bypass surgery required for a certain subset of patients with moyamoya disease.

METHODS

The authors retrospectively reviewed a total of 22 repeat bypass surgeries for 20 patients (age range 1-69 years) performed during the last 20 years at their institutions. The patients were classified into 2 groups. Group A included 10 patients who underwent repeat bypass surgery for anterior circulation due to insufficient revascularization on the ipsilateral side. Group B included 10 patients who underwent repeat bypass surgery for posterior circulation due to the involvement of the posterior cerebral artery (PCA) after successful initial surgery for anterior circulation.

RESULTS

Preoperative symptoms included headache in 3 patients, transient ischemic attack in 10, cerebral infarction in 3, and intracranial hemorrhage in 4 patients. Intervals between the initial bypass surgery and repeat bypass surgery were 0.3-30 years (median 3 years). In group A, superficial temporal artery to middle cerebral artery (MCA) anastomosis and indirect bypass were performed on 7 hemispheres. Only indirect bypass was performed on 3 hemispheres because of the lack of suitable donor or recipient arteries. In group B, occipital artery (OA) to PCA anastomosis and indirect bypass were conducted on 4 hemispheres, and OA-MCA anastomosis and indirect bypass on 1 hemisphere. Only indirect bypass was conducted on 7 hemispheres because of the lack of suitable recipient arteries. All 22 repeat bypass surgeries were successfully conducted. During follow-up periods (median 4 years), none of the patients suffered repeat stroke except 1 patient who died of recurrent intracerebral hemorrhage 3 years after repeat bypass surgery for anterior circulation.

CONCLUSIONS

Repeat bypass surgery was feasible and effective to reduce further incidence of headache attack, transient ischemic attack, and ischemic/hemorrhagic stroke in moyamoya disease patients. Through precise radiological analysis, surgical procedures should be planned to yield maximal therapeutic effects.

Radial Artery Fascial Flow-Through Free Flap for Complex Cerebral Revascularization: Technical Notes and Long-Term Neurologic and Radiographic Outcomes

BACKGROUND

Surgical innovation is critical for the management of challenging cerebrovascular pathology. Flow-through free flaps are versatile composite grafts that combine viable tissue with a revascularization source. Neurosurgical experience with these flaps is limited.

OBJECTIVE

To provide an in-depth technical description of the radial artery fascial (and fasciocutaneous) flow-through free flap (RAFF and RAFCF, respectively) for complex cerebral revascularizations.

METHODS

An Institutional Review Board-approved, prospective database was retrospectively reviewed to identify patients that underwent extracranial-to-intracranial cerebral bypass with a RAFF or RAFCF. Patient demographics, underlying pathology, surgical treatment, complications, and outcomes were recorded.

RESULTS

A total of 4 patients were treated with RAFFs or RAFCFs (average age 40 ± 8.8 yr). Two patients with progressive moyamoya disease involving multiple vascular territories with predominantly anterior cerebral artery (ACA) symptoms and flow alterations underwent combined direct ACA and indirect middle cerebral artery (MCA) bypass with a RAFF. The third patient with moyamoya disease and concomitant proximal fusiform aneurysms requiring internal carotid artery sacrifice underwent dual direct ACA and MCA bypass and indirect MCA revascularization with posterior tibial artery and RAFF grafts. The fourth patient with a large MCA bifurcation aneurysm and recurrent wound complications underwent a direct MCA bypass and complex wound reconstruction using a RAFCF. Good neurologic outcomes (Glasgow Outcomes Scale score ≥4 at discharge) were achieved in all patients. There were no perioperative surgical complications, and graft patency was confirmed on long-term follow-up.

CONCLUSION

The RAFF and RAFCF are versatile grafts for complex cerebral revascularizations.

Strategies for and Outcome of Repeat Revascularization Surgery for Moyamoya Disease: An American Institutional Series

BACKGROUND

Revascularization for moyamoya disease (MMD) effectively prevents future ischemic events. However, small subsets of patients with persistent or new symptoms due to inadequate collateralization require repeat revascularizations.

OBJECTIVE

To investigate the clinical and radiological outcome of repeat revascularization in MMD patients with previous indirect or direct bypasses.

METHODS

Single institution, retrospective analysis of a prospective MMD database.

RESULTS

From 1991 to 2014, this institution performed 1244 revascularization bypasses (1107 direct, 137 indirect) in 765 patients, of whom 57 were repeat revascularizations (38 indirect, 19 direct bypass). When initially performed at the institution, the repeat revascularization rate was 4% for indirect and 1% for direct bypasses (P = .03). Cohorts with previous indirect vs direct bypass were slightly younger (mean age 23 vs 30 yr), with fewer females (61% vs 84%, P = .08), and a similar mean duration between initial bypass and repeat revascularization (49 vs 47 mo). Both groups had similar repeat revascularization due to transient ischemic attacks (66% vs 63%). One acute graft occlusion in the previous direct bypass group was revised within 1 wk postoperatively. Over 50% of the repeat revascularizations in both groups were direct bypasses; the major difference being that the repeat bypass in the direct group was to augment another vascular territory. At nearly 5 yr mean follow-up, over 80% of patients in both groups are well, free from stroke/transient ischemic attack symptoms, with excellent radiological results.

CONCLUSION

Repeat revascularization can safely and effectively prevent future ischemic events. Indirect bypass has a higher rate of repeat revascularization than direct bypass.

[The use of high-flow extracranial-intracranial artery bypass in pathology of the cerebral and brachiocephalic arteries: technical features and surgical outcomes]

BACKGROUND

Poor outcomes of surgical treatment for complex cerebral aneurysms due to the development of cerebral ischemia were the cause to use cerebral revascularization surgery for this pathology.

OBJECTIVE

the study objective was to master a high-flow extracranial-intracranial (EC-IC) artery bypass technique and evaluate its application in surgical treatment of complex and giant cerebral aneurysms as well as complex lesions of the brachiocephalic arteries.

MATERIAL AND METHODS

Fifty two patients underwent high-flow IC-EC bypass surgery; of these, 34 patients had complex cerebral aneurysms, and 18 patients had complex stenotic occlusive lesions of the brachiocephalic arteries. After bypass placement, the patients with aneurysms underwent different variants of aneurysm exclusion (trapping or proximal clipping/ligation of the parent artery). All patients underwent follow-up studies of the bypass function and clinical condition in the early postoperative period and 6 and 12 months after surgery.

RESULTS

High-flow IC-EC bypass surgery is routinely used in clinical practice of the Novosibirsk Federal Center of Neurosurgery. Fifty one out of the 52 patients were followed-up in a range of 4 to 56 months. According to the direct or CT angiography data, bypasses functioned in 51 (98.1%) patients in the early and long-term postoperative periods. The clinical efficacy (no ischemic changes and improved cerebral perfusion) of high-flow IC-EC bypasses was demonstrated in 31 (91.2%) of 34 patients with aneurysms and in 17 (94.4%) of 18 patients with complex lesions of the brachiocephalic arteries. The total number of surgical complications was 8 (15.4%) cases: 7 complications occurred in patients with aneurysms, and 1 complication developed in a patient with bilateral ICA occlusion. Of these, ischemic complications developed in 4 (7.7%) cases, hemorrhagic complications occurred in 2 (3.8%) cases, and cranial nerve complications were found in 2 (3.8%) cases. One (1.9%) female patient with a giant aneurysm died from hemispheric stroke due to insufficient blood flow through the bypass.

CONCLUSION

Implementation of a large number of surgeries enabled improvement of the technique and clarification of the prerequisites for preoperative examination, intraoperative control, and postoperative management of patients. A low mortalits rate suggests this technique for use in clinical practice. The surgery is indicated for the treatment of giant aneurysms of the petrous, cavernous, and clinoid segments of the ICA. In the case of giant supraclinoid aneurysms, the surgery may be combined with removal of thrombotic masses from the aneurysm sac for rapid decompression of the cranial nerves. Application of this surgery for treatment of giant aneurysms of the trunk and bifurcation of the basilar artery is promising but requires further investigation. The surgery is also recommended for improving cerebral perfusion in the setting of complex stenotic occlusive lesions of the BCA: prolonged BCA stenoses, tandem ICA stenoses located in both the extracranial and intracranial segments, nonspecific vasculitis and arteriitis, subcranial aneurysms, kinking etc.

Radial Artery Fascial Flow-Through Free Flap for Combined Revascularization in Moyamoya Disease

BACKGROUND

Free flaps are commonly used by other surgical subspecialties for soft tissue reconstruction and revascularization. Cranial applications of these flaps have been limited to only a single case report.

OBJECTIVE

To present a new technique for combined revascularization in moyamoya disease using a flow-through free flap.

METHODS

Data were obtained from an Institutional Review Board-approved, prospectively maintained database with informed consent from the patient.

RESULTS

A 28-yr-old patient presented with progressive stenosis of the proximal anterior cerebral artery resulting in ischemic infarcts. Direct revascularization of the anterior cerebral artery territory and indirect revascularization of the middle cerebral artery with a large vascularized fascial pedicle was performed.

CONCLUSION

Flow-through free flaps offer a unique combination of revascularization and a large vascularized pedicle. This technique highlights the application of these flaps for revascularization in moyamoya disease and the value of multidisciplinary collaboration. Revascularization will likely play an increasing role in the open surgical treatment of cerebrovascular disease. We believe that flow-through free flaps will be a contribution to the future of revascularization in neurosurgery.