Embolization techniques of spontaneous direct carotid-cavernous fistulae: a single-center experience.

PURPOSE: Spontaneous direct carotid-cavernous fistula (CCF) are usually caused by a ruptured carotid cavernous aneurysm. We studied treatment of spontaneous direct CCFs in a single-center cohort of a high-volume tertiary referral center, reporting anatomical details, technical approaches of treatment, and outcomes. METHODS: Adult patients with a spontaneous direct CCF treated between 2010-2022 with follow-up MRI and/or DSA imaging available were retrospectively analyzed. We studied age, sex, clinical presentation, angiographic findings, treatment techniques, outcomes, and complications. RESULTS: Out of 80 patients with CCFs, twelve patients were treated for a non-traumatic direct CCF (15%) in 13 sessions. Median age was 65 years. Two patients had an underlying connective tissue disorder. In 10 cases, the direct CCF was caused by a ruptured cavernous carotid aneurysm. The direct CCFs were treated by endovascular transarterial embolization (10 cases), transvenous embolization (1 case), or surgery (1 case). Selective closure of the shunt was possible in 10 patients. Two patients were treated with parent vessel occlusion (PVO; one endovascular; one surgical, with bypass). Complications occurred in 2 / 12 patients (17%), with permanent morbidity in two patients (17%): trigeminal neuralgia after PVO and new infarct after surgical PVO and bypass. Selective closure of CCF resulted in no morbidity. There was no mortality in our series. CONCLUSION: Spontaneous direct CCFs are caused by rupture of a cavernous carotid aneurysm in most cases. Selective closure of the shunt, usually feasible transarterially with coils, achieves good results. Reconstructive endovascular techniques are preferred to minimize treatment related neurological complications.

Treatment of an intracranial aneurysm in the setting of fenestration of cranial division of the internal carotid artery: Technical considerations and a literature review.

Although rare, cerebral arterial fenestration may present challenges in diagnosis and treatment. Here we present a case of a supraclinoid internal carotid artery (ICA) fenestration adjacent to an ICA aneurysm, successfully treated with balloon-assisted coil embolization. A female in her 50's presented with an acute subarachnoid hemorrhage from a ruptured left ICA-ophthalmic artery (OA) aneurysm. Digital subtraction angiography revealed a focal ICA fenestration distal to the posterior communicating artery (Pcom). The patient underwent successful coil embolization of the aneurysm using the balloon-assisted technique. No immediate hemorrhagic, thromboembolic, or neurological complications were observed. The patient was discharged in good condition after 2 weeks of hospitalization. A comprehensive literature review of 33 cases was subsequently performed to understand the characteristics of this condition. Cases involving the cranial division of the ICA forming the fenestration exhibited caliber differences significantly more frequently (p = 0.02). Embryological insights revealed distinctions between the cranial divisions of the ICA, influencing fenestration morphology and associated aneurysm formation. Endovascular treatment poses the risk of vascular injury, necessitating the identification of this variation and procedural planning.

Atypical telencephalic reflux pattern in a cavernous sinus dural AV fistula related to an anatomical variation of the basal vein of Rosenthal.

Cavernous sinus dural arteriovenous fistula can cause cerebral edema and hemorrhage due to cortical venous reflux and congestion. Understanding complex venous reflux and drainage routes is crucial for treatment planning. Here, we present a case of a cavernous sinus dural arteriovenous fistula with cortical venous reflux via two separate terminations of the telencephalic veins caused by an aplastic basal vein of Rosenthal. The patient presented with diplopia and eye redness and was diagnosed with a Cognard type IIa + b cavernous sinus dural arteriovenous fistula. The shunt was supplied by the dural branches of the internal and external carotid arteries. Multiple shunt points involving the intercavernous sinus and the medial aspect of the left cavernous sinus were identified, with drainage into the supraorbital and intracranial veins, including two separate terminations of the telencephalic veins, one leading to the laterocavernous sinus via the superficial middle cerebral vein and the other to the cavernous sinus via the uncal vein, resulting in basal ganglia venous congestion in the absence of the basal vein of Rosenthal. During transvenous embolization, the intracranial veins, cavernous sinus, and intercavernous sinus were obliterated using a double-catheter technique with a combination of coils and liquid embolics. Telencephalic venous variations can lead to cavernous sinus drainage into the basal ganglia and orbitofrontal brain. This unique drainage pattern underscores the importance of recognizing anatomical variations when managing cavernous sinus dural arteriovenous fistula.

Current Practice: Rationale for Screening Children with Hereditary Hemorrhagic Telangiectasia for Brain Vascular Malformations.

BACKGROUND: Hereditary hemorrhagic telangiectasia is an autosomal dominant vascular dysplasia characterized by mucocutaneous telangiectasias, recurrent epistaxis, and organ vascular malformations including in the brain, which occur in about 10% of patients. These brain vascular malformations include high-flow AVMs and AVFs as well as low-flow capillary malformations. High-flow lesions can rupture, causing neurologic morbidity and mortality. STATE OF PRACTICE: International guidelines for the diagnosis and management of hereditary hemorrhagic telangiectasia recommend screening children for brain vascular malformations with contrast enhanced MR imaging at hereditary hemorrhagic telangiectasia diagnosis. Screening has not been uniformly adopted by some practitioners who contend that screening is not justified. Arguments against screening include application of short-term data from the adult A Randomized Trial of Unruptured Brain Arteriovenous Malformations (ARUBA) trial of unruptured sporadic brain AVMs to children with hereditary hemorrhagic telangiectasia as well as concerns about administration of sedation or IV contrast and causing patients or families increased anxiety. ANALYSIS: In this article, a multidisciplinary group of experts on hereditary hemorrhagic telangiectasia reviewed data that support screening guidelines and counter arguments against screening. Children with hereditary hemorrhagic telangiectasia have a preponderance of high-flow lesions including AVFs, which have the highest rupture risk. The rupture risk among children is estimated at about 0.7% per lesion per year and is additive across lesions and during a lifetime. ARUBA, an adult clinical trial of expectant medical management versus treatment of unruptured brain AVMs, favored medical management at 5 years but is not applicable to pediatric patients with hereditary hemorrhagic telangiectasia given the life expectancy of a child. Additionally, interventional, radiosurgical, and surgical techniques have improved with time. Experienced neurovascular experts can prospectively determine the best treatment for each child on the basis of local resources. The "watch and wait" approach to imaging means that children with brain vascular malformations will not be identified until a potentially life-threatening and deficit-producing intracerebral hemorrhage occurs. This expert group does not deem this to be an acceptable trade-off.

De Novo Brain Vascular Malformations in Hereditary Hemorrhagic Telangiectasia.

BACKGROUND: Approximately 10% of people with hereditary hemorrhagic telangiectasia (HHT) have brain vascular malformations (VMs). Few reports describe de novo brain VM formation. International HHT Guidelines recommend initial brain VM screening upon HHT diagnosis in children but do not address rescreening. We aimed to confirm whether brain VMs can form de novo in patients with HHT. METHODS: The Brain Vascular Malformation Consortium HHT project is a 17-center longitudinal study enrolling patients since 2010. We analyzed the database for de novo VMs defined as those detected (1) on follow-up neuroimaging in a patient without previous brain VMs or (2) in a location distinct from previously identified brain VMs and reported those in whom a de novo VM could be confirmed on central neuroimaging review. RESULTS: Of 1909 patients enrolled, 409 (21%) had brain VMs. Seven patients were recorded as having de novo brain VMs, and imaging was available for central review in four. We confirmed that three (0.7% of individuals with brain VMs) had de novo brain VMs (two capillary malformations, one brain arteriovenous malformation) with intervals of six, nine, and 13 years from initial imaging. Two with de novo brain VMs were <18 years. The fourth patient, a child, did not have a de novo brain VM but had a radiologically confirmed increase in size of an existing brain arteriovenous malformation. CONCLUSIONS: Brain VMs can, albeit rarely, form de novo in patients with HHT. Given the potential risk of hemorrhage from brain VMs, regular rescreening in patients with HHT may be warranted.

Posterior condylar canal dural arteriovenous fistula: anatomical, symptomatological, and therapeutic considerations in comparison with hypoglossal canal dural arteriovenous fistula.

BACKGROUND: Posterior condylar canal dural arteriovenous fistulas (dAVFs) are extremely rare. METHODS: We report a case series and literature review of posterior condylar canal dAVFs and discuss similarities and differences between posterior condylar and hypoglossal canal dAVFs with respect to the related vascular anatomy, angioarchitecture of the fistula, presentation, and treatment. RESULTS: Four cases of posterior condylar canal dAVF were identified at our institutions and six cases were identified in the literature. Posterior condylar canal dAVFs were predominantly frequent in relatively young women. All patients presented with pulsatile tinnitus. There was no history of hemorrhage as there was no cortical venous reflux. This is different from hypoglossal canal dAVFs which can present with myelopathy or hemorrhage from cortical venous reflux. Transvenous embolization was safe and eliminated the symptoms. Palliative transarterial embolization can be an option to mitigate the symptoms, although there is a potential risk of cranial nerve palsy or lateral medullary stroke. CONCLUSIONS: Posterior condylar canal dAVFs are generally benign lesions. However, intolerable tinnitus may require intervention. Transvenous embolization is effective and safe.

Brain AVM compactness score in children with hereditary hemorrhagic telangiectasia.

OBJECTIVE: The brain arteriovenous malformation (BAVM) nidus compactness score (CS), determined on angiography, predicts BAVM recurrence after surgical resection among children with sporadic BAVMs. We measured the angiographic CS for BAVMs among children with hereditary hemorrhagic telangiectasia (HHT) to determine CS characteristics in this population. METHODS: A pediatric interventional neuroradiologist reviewed angiograms to determine the CS of BAVMs in children with HHT recruited to the BVMC. CS is based on overall nidus and perinidal anomalous vessel compactness. CS categories included 1 = diffuse nidus, 2 = intermediate nidus, and 3 = compact nidus. RESULTS: Forty-eight of 78 children (61.5%) with HHT and brain vascular malformations had a conventional angiogram; 47 (97.9%) angiograms were available. Fifty-four BAVMs were identified in 40 of these 47 children (85.1%). Of 54 BAVMs in children with HHT, CS was 1 in 7 (13%), 2 in 29 (53.7%), and 3 in 18 BAVMs (33.3%) compared with CS of 1 in six (26.1%), 2 in 15 (65.2%), and 3 in 2 BAVMs (8.7%) among 23 previously reported children with sporadic BAVMs, p = 0.045 (Fisher's exact). Seven children with HHT had intracranial hemorrhage: 4 had CS = 3, 1 had CS = 2, and 2 had CS = 1. CONCLUSIONS: A range of CSs exists across HHT BAVMs, suggesting it may be an angiographic measure of interest for future studies of BAVM recurrence and hemorrhage risk. Children with HHT may have more compact niduses compared to children with sporadic BAVMs. Additional research should determine whether CS affects hemorrhage risk or post-surgical recurrence risk in HHT-associated BAVMs, which could be used to direct BAVM treatment.

Transarterial Embolization of Dural Arteriovenous Fistulas: Conventional, Pressure Cooker, and Microballoon Catheter Embolization Techniques.

BACKGROUND AND OBJECTIVES: Dural fistulas are abnormal connections between dural arteries and intracranial veins treated mainly endovascularly in most settings. The aim was to examine a single-institution experience of microballoon catheter transarterial embolization (TAE) of dural arteriovenous fistulas (dAVFs) and compare it with other TAE techniques. METHODS: We retrospectively identified all dAVFs treated at our institution between 2017 and 2022 with microballoon, conventional, and pressure cooker TAE. We studied occlusion and retreatment rates, treatment-related complications, and radiation doses. RESULTS: During the study period, 66 patients underwent 75 TAE procedures to treat 68 dAVFs: 47 conventional TAE, 14 pressure cooker TAE, and 14 microballoon TAE. Median age of the study population was 63 years with 32% females. The most common dAVF location was the transverse sinus and 20% of dAVFs presented with hemorrhage. At 3-month follow-up, stable complete occlusion of the dAVF was seen in 72% (n = 34) after conventional TAE, 79% (n = 11) after pressure cooker TAE, and 86% (n = 12) after microballoon TAE. Retreatment was required in 19% (n = 9) after conventional TAE, 7% (n = 1) after pressure cooker TAE, and 7% (n = 1) after microballoon TAE. Treatment-related complications occurred in 17% (n =) after conventional TAE, 29% (n = 4) after pressure cooker TAE, and 7% (n = 1) after microballoon TAE. CONCLUSION: In our experience, microballoon TAE of dAVFs resulted in better initial and 3-month angiographic outcomes and required less retreatment than conventional TAE. Microballoon TAE also resulted in fewer treatment-related complications than other techniques. In our experience, microballoon TAE is a reliable and safe endovascular technique to treat dAVFs.

Carotid stenting for symptomatic carotid artery web: Multicenter experience.

OBJECTIVE: Carotid artery webs are an underappreciated cause of recurrent ischemic stroke, and may represent a significant portion of cryptogenic stroke. Evidence-based guidelines for the management of symptomatic carotid webs do not exist. The goal of this study is to audit our local experience for patients with symptomatic carotid artery webs undergoing carotid stenting as a treatment option, along with describing the hypothesized dynamic physiology of carotid webs. METHODS: All patients undergoing stenting for symptomatic carotid artery web at two comprehensive regional stroke centers with high endovascular thrombectomy volume from January 1, 2012 to March 1, 2021 were included. The modified Rankin Scale (mRS) score was used to define functional outcome at 3 months after stenting. RESULTS: Fourteen consecutive patients with symptomatic carotid artery webs underwent stenting. Twelve patients were female (86%), with a median age of 54 (IQR, 48-64) years across all patients. Stroke was the qualifying event in 12 (86%) patients and TIA in 2. Eleven patients (11/14, 79%) achieved a mRS score of 0-2 at 90 days, 2 (14%) were mRS 3-5, and one patient was lost to follow-up. The median follow-up was 12 months (IQR, 10-12). There was no recurrent stroke or TIA like symptoms in any patients. CONCLUSIONS: Carotid stenting appears to be safe at preventing recurrent stroke/TIA with a median follow-up of 12 months in this retrospective multicenter observational study.

Delayed Foreshortening and Prolapse of Silk Vista Baby into Superior Cerebellar Artery Aneurysm.

BACKGROUND: Flow diversion has evolved as a minimally invasive treatment for intracranial aneurysms. The Silk Vista Baby (SVB) can be navigated into small cerebral vessels because it can be deployed through a low-profile microcatheter. METHODS: We report on treating a patient in his 70s with an unruptured fusiform right superior cerebellar artery aneurysm using an SVB. RESULTS: Significant foreshortening of the device was noted during the initial procedure; however, the position was satisfactory with good apposition and clearance of the aneurysm neck. A stable position of the SVB on 1-day and 2-month postprocedural computed tomography angiography was also demonstrated. Subsequently, a 6-month follow-up computed tomography angiography detected delayed foreshortening and prolapse of the SVB into the aneurysm, for which an additional SVB was placed in a second procedure. There were no complications and the patient remained clinically well. CONCLUSIONS: Although the intraoperative foreshortening was not unexpected, the delayed postprocedural behavior of proximal foreshortening and subsequent prolapse of the SVB into the aneurysm have not been previously described. We would like to share this for awareness in this technical note.

Prevalence and Characteristics of Intracranial Aneurysms in Hereditary Hemorrhagic Telangiectasia.

BACKGROUND AND PURPOSE: The association between hereditary hemorrhagic telangiectasia and intracranial aneurysms remains controversial. This study evaluated the prevalence and characteristics of intracranial aneurysms in patients with hereditary hemorrhagic telangiectasia with brain vascular malformations. MATERIALS AND METHODS: Between 2007 and 2021, patients enrolled in the Brain Vascular Malformation Consortium with definite hereditary hemorrhagic telangiectasia, the presence of brain vascular malformations, and available angiographic studies of the brain were retrospectively reviewed. Angiographic features of intracranial aneurysms and their relationship to coexisting brain vascular malformations were analyzed. We also examined the association between baseline clinical features and the presence of intracranial aneurysms. RESULTS: One hundred eighty patients were included. A total of 14 intracranial aneurysms were found in 9 (5%) patients, and 4 intracranial aneurysms were considered flow-related aneurysms. Patients with intracranial aneurysms were significantly older than patients without intracranial aneurysms (mean, 48.1 [SD, 18.2] years versus 33.5 [SD, 21.0] years; P = .042). If we excluded flow-related intracranial aneurysms, the prevalence of intracranial aneurysms was 3.3%. All intracranial aneurysms were in the anterior circulation, were unruptured, and had an average maximal diameter of 3.9 (SD, 1.5) mm. No intracranial aneurysms were found in pediatric patients with hereditary hemorrhagic telangiectasia. No statistically significant correlation was observed among other baseline demographics, hereditary hemorrhagic telangiectasia features, and the presence of intracranial aneurysms. CONCLUSIONS: The prevalence of intracranial aneurysms in this large cohort study is comparable with that in the general population and might be increased slightly due to hemodynamic factors associated with shunting brain vascular malformations.

Reply to Eker et al. Comment on "Kilian et al. Comparing Characteristics and Treatment of Brain Vascular Malformations in Children and Adults with HHT. J. Clin. Med. 2023, 12, 2704".

We are grateful to Eker et al. for their thoughtful analysis and response to our publication titled Comparing Characteristics and Treatment of Brain Vascular Malformations in Children and Adults with HHT [...].

Utilisation of the Scepter Mini dual-lumen balloon - An illustrative series.

BACKGROUND: Dual-lumen balloon microcatheters can aid in the safety and efficacy of endovascular embolisation of cerebrospinal vascular malformations. The Scepter Mini dual-lumen balloon is a novel device with a smaller profile than previous balloon microcatheters, opening up new indications not only in the treatment of cerebrospinal malformations but in various other neurovascular therapeutic and diagnostic scenarios. METHODS: Following institutional ethics review board approval, a retrospective review of our prospectively maintained database of cases employing the Scepter Mini dual-lumen microballoon catheter was conducted. Five cases in particular were highlighted, demonstrating utilisation of this device, which may be of interest to the Neurointerventionalist. Patient demographics, procedure details, complications and clinical outcome data were reviewed. RESULTS: Five cases employing the Scepter Mini dual-lumen microballoon catheter are presented; trans-arterial embolisation of cerebral AVM, pre-operative tumour embolisation, diagnostic angiography, trans-venous embolisation of cerebral AVM and trans-arterial embolisation of DAVF. No intraprocedural complications were recorded, one patient had a delayed haemorrhage. CONCLUSION: Potential utilisation of the Scepter Mini lies not only in the trans-arterial embolisation of cerebrospinal vascular malformations, but in a range of other diagnostic and therapeutic indications as demonstrated.

Intraoperative intraarterial indocyanine green video-angiography for disconnection of a perimedullary arteriovenous fistula: illustrative case.

BACKGROUND: Intraarterial (IA) indocyanine green (ICG) angiography is an intraoperative imaging technique offering special and temporal characterization of vascular lesions with very fast dye clearance. The authors' aim is to demonstrate the use of IA ICG angiography to aid in the surgical treatment of a perimedullary thoracic arteriovenous fistula (AVF) in a hybrid operating room (OR). OBSERVATIONS: A 31-year-old woman with a known history of spinal AVF presented with 6 weeks of lower-extremity weakness, gait imbalance, and bowel/bladder dysfunction. Magnetic resonance imaging revealed an extensive series of flow voids across the thoracic spine, most notably at T11-12. After partial embolization, she was taken for surgical disconnection in a hybrid OR. Intraoperative spinal digital subtraction angiography was performed to identify feeding vessels. When the target arteries were catheterized, 0.05 mg of ICG in 2 mL of saline was injected, and the ICG flow in each artery was recorded using the microscope. With an improved surgical understanding of the contributing feeding arteries, the authors achieved complete in situ disconnection of the AVF. LESSONS: IA ICG angiography can be used in hybrid OR settings to illustrate the vascular anatomy of multifeeder perimedullary AVFs and confirm its postoperative disconnection with a fast dye clearance.

Use of the neuroform atlas for stenting of intracranial atherosclerotic disease: Clinical and angiographic outcomes.

BACKGROUND: Intracranial atherosclerotic disease (ICAD) is a potential cause of ischemic stroke. Treatment of ICAD can include intracranial stenting. There are specifically designed stents for this use-case; however, less is known about the off-label use of the Neuroform Atlas stent. In this study, we describe the outcomes of the Neuroform Atlas stent for treatment of ICAD. METHODS: Adult patients with symptomatic ICAD failing best medical treatment undergoing elective intracranial stenting using the Neuroform Atlas stent between November 2018 and March 2021 were included. Patient demographics, procedure-related details and clinical and imaging outcomes were analyzed. RESULTS: Eighteen patients met the inclusion criteria, with a mean follow-up duration of 9.6 ± 6.8 (standard deviation) months. There were two procedure-related mortalities (one massive intracranial hemorrhage and one groin site complication with sepsis). Fifteen patients were alive at the 6-month follow-up, all with satisfactory stent patency on follow-up imaging without any new ischemic events. Modified Rankin Scale at latest follow-up was 1.9 (interquartile range 5). CONCLUSION: In this single-center consecutive series, intracranial stenting with the Neuroform Atlas stent was a safe and effective treatment for symptomatic ICAD patients failing best medical management.

Anatomical considerations regarding a high-flow arteriovenous fistula below the conus medullaris in a patient with hereditary hemorrhagic telangiectasia: Case report.

BACKGROUND AND IMPORTANCE: Cauda equina radicular arteriovenous fistulas are rare "low flow" shunting lesions characterized by direct communication between the radicular artery and vein of a cauda equina nerve root. None have been associated with hereditary hemorrhagic telangiectasia and a high-flow cauda equina radicular arteriovenous fistula has never been reported. We present a unique case of a high-flow cauda equina radicular arteriovenous fistula in a patient with hereditary hemorrhagic telangiectasia. Marked flow-induced vascular remodeling posed significant diagnostic and therapeutic challenges which will be highlighted in this report. CLINICAL PRESENTATION: A 39-year-old female with genetically confirmed hereditary hemorrhagic telangiectasia presented with progressive thoracic myelopathy secondary to a high-flow single-hole arteriovenous fistula below the conus. The feeding artery, arising from the anterior spinal artery, and draining vein had a paramedian course, favoring the diagnosis of a cauda equina radicular arteriovenous fistula (supplied by a proximal radicular artery) over a filum terminale arteriovenous fistula. Transarterial embolization was attempted but significant elongation and tortuosity of the anterior spinal artery precluded microcatheter access to the fistulous point. Surgical disconnection was successfully performed. The intraoperative findings supported the diagnosis of cauda equina radicular arteriovenous fistula. Delayed neurologic deterioration secondary to overshooting venous thrombosis was observed. She recovered after the initiation of therapeutic anticoagulation. CONCLUSION: To the best of our knowledge, we hereby report the first high-flow cauda equina radicular arteriovenous fistula. The accurate differentiation of cauda equina radicular arteriovenous fistula from filum terminale arteriovenous fistulas, while challenging, is important to avoid treatment-related complications. Careful preoperative planning, the use of specialized endovascular and surgical techniques, and meticulous postoperative care can ensure the safe and complete disconnection of high-flow cauda equina radicular arteriovenous fistulas.

A dual-center validation of the PIRAMD scoring system for assessing the severity of ischemic Moyamoya disease.

Background: Prior Infarcts, Reactivity, and Angiography in Moyamoya Disease (PIRAMD) is a recently proposed imaging-based scoring system that incorporates the severity of disease and its impact on parenchymal hemodynamics in order to better support clinical management and evaluate response to intervention. In particular, PIRAMD may have merit in identifying symptomatic patients that may benefit most from revascularization. Our aim was to validate the PIRAMD scoring system. Methods: Patients with ischemic Moyamoya disease, who underwent catheter angiographic [modified Suzuki Score (mSS) and collateralization status], morphological MRI and a parenchymal hemodynamic evaluation with blood oxygenation-level dependent cerebrovascular reactivity (BOLD-CVR) at two transatlantic centers, were retrospectively included. The primary outcome was the presence of neurological symptoms. The diagnostic capacity of each PIRAMD feature alone was evaluated, as well as combined and the inter-institutional differences of each parameter were evaluated. Results: Seventy-two hemispheres of 38 patients were considered for analysis, of which 39 (54%) were classified as symptomatic. The presence of a prior infarct had the highest odds ratio [odds ratio (OR) =24; 95% CI: 6.7-87.2] for having neurological symptoms, followed by impaired CVR (OR =17; 95% CI: 5-62). No inter-institutional differences in the odds ratios or area under the curve (AUC) were found for any study parameter. The PIRAMD score had an AUC of 0.88 (95% CI: 0.80-0.96) with a similar AUC for the PIRAMD grading score. Conclusions: Our multicentric validation of the recently published PIRAMD scoring system was highly effective in rating the severity of ischemic Moyamoya disease with excellent inter-institutional agreement. Future studies should investigate the prognostic value of this novel imaging-based score in symptomatic patients with Moyamoya disease.