Cranial dural arteriovenous shunts: selection of the ideal lesion for surgical occlusion according to the classification system.

BACKGROUND: The types of cranial dural arteriovenous fistulae (cDAVFs) that constitute good surgical candidates are unclear despite the use of classifications. We aimed to compare the DES classification with other classification schemes in identifying "ideal lesions for surgery." The DES scheme is based on two features: the level of the shunt (BVS, bridging vein shunt; DSS, dural sinus shunt; ISS, isolated sinus shunt; EVS, emissary vein shunt) and the type of leptomeningeal venous reflux (LVR) (direct, exclusive, strained). METHODS: In this observational cohort study, the angiographies of 20 consecutive patients treated over 1 year were analyzed retrospectively. We defined cDAVFs as ideal for surgery, if cure may be achieved by disconnecting the arterialized draining vein through a single craniotomy. To evaluate the performance of each classification scheme in identifying the "ideal lesion for surgery," we carried out a sensitivity analysis of the Borden, Cognard, and DES schemes. RESULTS: Eight lesions were Borden type 3 and 1 type 2, and 11 type 1. According to Cognard, 2 lesions were type IV, 2 type III, 1 type IIa+b, 11 type I, and 4 lesions could not be clearly classified. According to the DES scheme, 8 lesions were DSS, 4 BVS, 3 ISS, and 5 EVS. All 4 lesions classified as BVS in the DES were ideal lesions for surgery (sensitivity, specificity, PPV, NPV 100%). Not all high-grade lesions according to Borden were good surgical candidates. CONCLUSION: The DES scheme, as opposed to other classifications, facilitates the therapeutic decision-making especially for selecting candidates for surgery.

Carotid Cavernous Fistulas and Dural Arteriovenous Fistulas of the Cavernous Sinus: Validation of a New Classification According to Venous Drainage.

BACKGROUND: Multiple carotid cavernous fistula (CCF) classifications have been proposed. However, they lacked predictive factors for the clinical presentation, natural history, and hemorrhagic risk. Our aim was to externally validate a new classification according to venous drainage (i.e., the Thomas classification [TC]) to assess its relationship with symptoms, endovascular treatment, and outcomes. METHODS: We performed a multicenter retrospective review of CCFs at 2 major academic institutions. The CCFs were classified using the Barrow classification (BC) and TC systems. RESULTS: The data from 94 patients with a diagnosis of CCF were collected during a study period 23 years, 4 months. Of these 94 patients, 89 had undergone CCF treatment and 5 had experienced spontaneous occlusion. Complete occlusion was achieved in 89.9% of the treated patients. Complications occurred in 5.3% of the patients, including permanent deficits in 2.1%. TC type 4 was associated with cortical symptoms compared with type 2 (P = 0.003) and type 3 (P < 0.001). The BC was not able to detect significant differences among the symptom types. Significant differences were found using the TC for the transarterial-only, transvenous anterior-only, and transvenous posterior-only approaches (P < 0.001, P = 0.03, and P = 0.001, respectively). The transvenous posterior and transvenous anterior approach were significantly associated with type 2 and 3 TC, respectively. Excluding direct CCFs, the BC was not related to the treatment approach. No significant differences in the outcomes were found. However, a trend toward a lower occlusion rate for TC type 4 compared with type 3 was observed. CONCLUSION: The TC provided useful information regarding the fistula anatomy and venous hemodynamics, which correlated with the clinical symptoms and treatment strategy.

Three-Dimensional Evaluation and Classification of the Anatomy Variations of Vertebral Artery at the Craniovertebral Junction in 120 Patients of Basilar Invagination and Atlas Occipitalization.

BACKGROUND: Patients with basilar invagination and atlas occipitalization usually present abnormal anatomy of the vertebral arteries (VAs) at the craniovertebral junction (CVJ). OBJECTIVE: To describe and further classify different types of VA variations at the CVJ with 3D visualization technology. METHODS: One hundred twenty patients with basilar invagination and atlas occipitalization who had undergone 3-dimensional computed tomographic angiography (3D-CTA) were retrospectively studied. Imaging data were processed via the separating, fusing, opacifying, and false-coloring-volume rendering technique. Abnormal anatomy of the VA at the CVJ was categorized and related anatomic parameters were measured. RESULTS: Seven different types were classified. Type I, VAs enter the cranium after leaving VA groove on the posterior arch of atlas (26.7% of 240 sides); Type II, VAs enter an extraosseous canal created in the assimilated atlas lateral mass-occipital condyle complex before reaching the cranium (53.3%); Type III, VA courses above the axis facet or curves below the atlas lateral mass then enter the cranium (11.7%); Type IV, VAs enter the spinal canal under the axis lamina (1.3%); Type V, high-riding VA (31.3%); Type VI, fenestrated VA (2.9%); Type VII, absent VA (4.2%). Distance from the canal of Type II VA to the posterior facet surface of atlas lateral mass (5.51 ± 2.17 mm) means a 3.5-mm screw can be safely inserted usually. Shorter distance from the midline (13.50 ± 4.35) illustrates potential Type III VA injury during exposure. Decreased height and width of axis isthmus in Type V indicate increased VA injury risks. CONCLUSION: Seven types of VA variations were described, together with valuable information helpful to minimize VA injury risk intraoperatively.

The variant with the absence of the superior petrosal venous and sinus: A potential pitfall of transvenous balloon-assisted embolisation of Borden type II transverse-sigmoid dural arteriovenous fistula.

We describe a patient with Borden type II transverse-sigmoid dural arteriovenous fistula. On the venous phase of the left vertebral artery injection, there was no superior petrosal veins and sinus on the side of lesion. After transvenous balloon-assisted Onyx embolisation, the patient developed extensive venous infarction from venous occlusion. This report calls attention to a highly unusual variant in which the superior petrosal veins and sinus are absent, and the cerebellar veins will be drained by tributaries of the bridging veins in this circumstance. In such circumstances, occlusion of the bridging vein on the tentorial cerebellar surface may lead to complications during transverse-sigmoid dural arteriovenous fistula embolisation.

[Subcortical calcification on CT in Borden type III intracranial dural arteriovenous fistula].

We herein report a 67-year-old female who presented with progressive dementia and disturbance of consciousness. Brain CT showed multiple subcortical calcifications with edema. Enhanced CT showed multiple abnormal vessels in the left hemisphere. Electroencephalography indicated diffuse spike and slow wave complex, so non-convulsive status epilepticus was diagnosed. Cerebral angiography revealed several feeder arteries with retrograde leptomeningeal venous drainage. We diagnosed her with Borden type III cerebral dural arteriovenous fistulas. Trans-arterial embolization with n-butyl-2-cyanoacrylate was performed, and she has experienced no epileptic attacks for at least ten months. Calcification changes are sometimes seen in Borden type II dural arteriovenous fistulas but not in aggressive types, such as Borden type III. It is important to suspect dural arteriovenous fistulas when we encounter patients with progressive dementia or/and epilepsy with cerebral calcification lesions, as this may be a treatable disease condition.

Electrophysiological Assessment and Classification of Motor Pathway Function in Patients With Spinal Dural Arteriovenous Fistula.

PURPOSE: The diagnosis of spinal dural arteriovenous fistula (SDAVF) is difficult and often delayed because clinical features are often nonspecific. We assessed the motor function electrophysiologically in patients with SDAVF. METHODS: Motor-evoked potentials after transcranial magnetic stimulation and compound muscle action potentials and F-waves after electrical stimulation in the ulnar and tibial nerves were measured from the abductor hallucis (AH) muscles in 14 patients with SDAVF (SDAVF group), 12 patients with compressive thoracic myelopathy (CTM group), and 16 normal subjects (control group). The peripheral conduction time determined from abductor hallucis muscles (PCT-AH) and the central motor conduction time determined from abductor hallucis muscles (CMCT-AH) were calculated. According to the neurological findings, patients in the SDAVF group were classified to upper motor neuron (UMN) sign and lower motor neuron (LMN) sign categories. RESULTS: CMCT-AH in the SDAVF and CMT groups were significantly longer than those in the control group. PCT-AH in the SDAVF group was significantly longer than that in the control and CMT groups. Twelve patients in the SDAVF group showed abnormal CMCT-AH and/or PCT-AH. Abnormal CMCT-AH and PCT-AH were detected in five cases that exhibited UMN sign and/or LMN sign. Three cases with abnormal CMCT-AH and normal PCT-AH exhibited UMN sign. LMN sign without UMN sign was observed in four cases with abnormal PCT-AH and normal CMCT-AH. CONCLUSIONS: Our study revealed abnormalities in the corticospinal tract and/or lower motor neurons, and classified the patients with SDAVF into three types: the UMN type, LMN type, and mixed type.

Falcotentorial Location of Dural Arteriovenous Fistulas Derived from the Neural Crest as a Risk Factor for Aggressive Clinical Course.

The topographical distribution of dural arteriovenous fistulas (DAVFs) was analyzed based on the embryological anatomy of the dural membrane. Sixty-six consecutive cases of intracranial and spinal DAVFs were analyzed based on the angiography, and each shunt point was identified according to the embryological bony structures. The area of dural membranes was categorized into three different groups: a ventral group located on the endochondral bone (VE group), a dorsal group on the membranous bone (DM group), and a falcotentorial group (FT group) in the falx cerebri, tentorium cerebelli, falx cerebelli, and diaphragma sellae. The FT group was derived from the neural crest and designated when the dural membrane was formed only with the dura propria (meningeal layer of the dura mater) and not from the endosteal dura. Olfactory groove, falx, tent of the cerebellum, and nerve sleeve of spinal cord were categorized in the FT group, which presented later in life and which had a male predominance, more aggressive clinical presentations, and significant cortical and spinal venous reflux. The FT group was formed only with the dura propria that was considered as an independent risk factor for aggressive clinical course and hemorrhage of DAVFs.

[The spinal dural arteriovenous fistula is an underdiagnosed vascular malformation].

The spinal dural arteriovenous fistula is the most common spinal vascular malformation, and it is severely underdiagnosed. The symptoms can mimic those of spinal stenosis. Today, the diagnosis is made by an advantageous combination of MR time-resolved imaging of contrast kinetics and digital subtraction angiography posing low risk to the patient. Treatment is primarily direct microsurgical obliteration. Early treatment is essential, since outcome is dependent on preoperative clinical status.

Dural arteriovenous fistula of the lateral foramen magnum region: A review.

The lateral foramen magnum region is defined as the bilateral occipital area that runs laterally up to the jugular foramen. The critical vasculatures of this region are not completely understood. Dural arteriovenous fistulas that occur in this region are rare and difficult to treat. Therefore, we searched PubMed to identify all relevant previously published English language articles about lateral foramen magnum dural arteriovenous fistulas, and we performed a review of this literature to increase understanding about these fistulas. Four types of dural arteriovenous fistulas occur in the lateral foramen magnum region. These include anterior condylar confluence and anterior condylar vein dural arteriovenous fistulas, posterior condylar canal dural arteriovenous fistulas, marginal sinus dural arteriovenous fistulas, and jugular foramen dural arteriovenous fistulas. These dural arteriovenous fistulas share similar angioarchitectures and clinical characteristics. The clinical presentations of lateral foramen magnum dural arteriovenous fistulas include pulsatile tinnitus, intracranial hemorrhage, myelopathy, orbital symptoms, and cranial nerve palsy. Currently, head computed tomography, computed tomography angiography, magnetic resonance imaging, magnetic resonance angiography and digital subtraction angiography (DSA) are useful for diagnosing dural arteriovenous fistulas, and of these, DSA remains the "gold standard." Most lateral foramen magnum dural arteriovenous fistulas need to be treated due to their aggressive symptoms, and transvenous embolization presents the best options. During treatment, it is critical to accurately place the microcatheter into the fistula point, and intraoperative integrated computed tomography and DSA data are very helpful. Other treatments, such as transarterial embolization, microsurgery or conservative treatment, can also be chosen. After appropriate treatment, most patients with lateral foramen magnum dural arteriovenous fistulas achieve satisfactory outcomes.

Distally Enlarged Feeding Artery Phenomenon in Intracranial Dural Arteriovenous Fistula: Alternative Access Route to Transarterial Intravenous Embolization.

BACKGROUND: Transvenous (TV) embolization is ideal for endovascular treatment of intracranial dural arteriovenous fistulas (DAVF). However, it is not always feasible because of various factors, and transarterial (TA) embolization could then be tried. We aimed to determine the incidence of distally enlarged feeding artery phenomenon and the major feeding artery in DAVF. If the TV approach is difficult and this phenomenon is observed, we could use this vessel for transarterial intravenous (TAIV) embolization as an endovascular treatment modality for DAVF. METHODS: Forty-four patients with intracranial DAVF treated by the endovascular procedure between 2009 and 2016 were retrospectively reviewed. Their clinical records, angiography reports, and embolization procedure notes were studied, and their angiographies were chronologically classified into proliferative and restrictive types. RESULTS: In 14 of 44 patients (32%), we observed the distally enlarged feeding artery phenomenon. The most common enlarged artery was the middle meningeal artery. The distally enlarged feeding artery group was predominantly the restrictive type, and the other group was proliferative in nature (P < 0.001). Of the 14 patients, 7 underwent TAIV embolization, and the other 7 underwent TV embolization. CONCLUSIONS: Distally enlarged feeding artery phenomenon was observed in 32% of patients with intracranial DAVF. This group was predominantly the restrictive type. We conclude that this phenomenon might help determine a patient's eligibility for TAIV embolization when TV embolization is difficult or impossible.

Correlation of Aggressive Intracranial Lesions and Venous Reflux Patterns in Dural Arteriovenous Fistulas.

BACKGROUND: The association between venous reflux patterns with aggressive intracranial lesions (AILs), including intracranial edema (IE), intraparenphymal hemorrhage (IPH), and subarachnoid hemorrhage (SAH), has not been well established in cranial dural arteriovenous fistulas (DAVFs). We propose an updated classification system based on venous drainage. METHODS: We retrospectively assessed the catheter angiography findings of venous drainage patterns. Cranial DAVFs with no reflux flow and those with reflux flow drainage into the sinus only, the bridge vein only, the bridge vein and pial vein, and the sinus, bridge vein, and pial vein were designated as types 1, 2, 3, 4, and 5, respectively. We analyzed the associations between venous reflux patterns with AILs in 73 patients with DAVFs. RESULTS: AILs were found in 43 patients (58.9%), including 8 (11%) with SAH, 8 (11%) with IPH, and 27 (36.9%) with IE. Our proposed classification scheme was significantly associated with AILs (P < 0.001). SAH was found in patients with type 3 (62.5%) and type 4 (37.5%), whereas IPH was seen mostly in those with type 4 (87.5%). The proportion of IE gradually increased from type 3 to type 5 (11.1% to 29.6% to 59.2%). Significant difference was found among each type between complete resolution and uncompleted resolution after endovascular treatment (P = 0.034), which also demonstrated a gradually increasing proportion of uncompleted resolution from type 1 to type 5 (4.5%, 4.5%, 9.1%, 31.8%, and 50%). CONCLUSIONS: Our proposed classification system effectively demonstrates a correlation between venous reflux patterns and AILs and outcomes of endovascular treatment in patients with DAVFs.

Spinal Arteriovenous Shunts: Angioarchitecture and Historical Changes in Classification.

The purposes of this study were to review historical changes in the classification of spinal arteriovenous (AV) shunts and to propose a practical classification system. The associated literature regarding the classification of spinal AV shunts was reviewed in the angiography era between 1967 and 2015. The classification systems of spinal AV shunts and a proposed classification system were presented with neuroradiological imaging and medical illustrations. There have been seven major classification systems based on the evolution of diagnostic methods as well as treatments for spinal AV shunts: the first description of spinal AV shunts diagnosed and classified using spinal angiography in 1971; the second classification based on a case report of intradural direct perimedullary arteriovenous fistulas (AVFs) treated by microsurgery in 1987; the third classification based on a case series of intradural perimedullary AVFs treated by endovascular interventions in 1993; the fourth and fifth classification systems based on a case series of spinal AVFs and arteriovenous malformations (AVMs) treated by microsurgery or endovascular interventions in 2002; the sixth classification based on a case series of cranio-spinal dural AV shunts in 2009; and the seventh classification based on a case series of extradural AVFs treated by microsurgery and endovascular interventions in 2011. Based on historical reports, the author proposed a classification system according to the sites (dural, intradural, and extradural) and types (AVF and AVM) of AV shunts. By learning the historical background, we may obtain a clearer understanding of the complex and confusing classification system of spinal AV shunts.

Classification and pathophysiology of spinal vascular malformations.

Spinal arteriovenous malformations and fistulas comprise spinal vascular malformations (sVMs), a rare but challenging neurosurgic entity. A number of mechanisms have been proposed as explanations of neurologic decline in the setting of arteriovenous shunting, including venous hypertension, venous congestion, hemorrhage, vascular steal, or mass effect, which can be worsened with venous varices or aneurysmal dilations. Anatomic location and features dictate the categorization of sVMs. Two major systems are in place for classification of sVMs - (1) the American/French/English connection and (2) the Spetzler system - as well as a number of systems that have been described over the past century.

Spinal arteriovenous malformations: surgical management.

Spinal arteriovenous malformations (AVMs) are a diverse population of vascular lesions associated with significant long-term morbidity and neurologic impairment. Spinal AVMs can be classified into three categories: intramedullary, extradural-intradural, and conus, depending on their angioarchitecture and anatomy. Extradural-intradural lesions are typically incurable due to their diffuse nature, but patients may benefit from targeted therapy of symptomatic components. Intramedullary and conus AVMs are amenable to safe surgical resection when combined with endovascular embolization and use of a pial dissection technique that spares entry into the neural parenchyma.

Transvenous Coil Embolization of Cavernous Sinus Dural Arteriovenous Fistula on a Revised Classification.

BACKGROUND: Transvenous coil embolization is an effective method to manage cavernous sinus dural arteriovenous fistulas (CSDAVFs). However, some CSDAVFs may be associated with complex angioarchitecture, leading to difficult access. In this article we report our experience with coil embolization of CSDAVFs. METHODS: Over a 5-year period, 70 patients (24 men and 46 women; mean age, 60 years) underwent coil embolization of a total of 73 CSDAVFs at our institution. We retrospectively analyzed and categorized the CSDAVFs based on a revised classification scheme as proliferative type (PT), restrictive type (RT), or late restrictive type (LRT). Outcomes of embolization in each type were evaluated. RESULTS: Pial vein reflux was seen in 2 PT (10%), 10 RT (37%), and 15 LRT (60%) CSDAVFs (P = 0.005). Para-CS fistula components were found in 12 PT (57%), 1 RT (4%), and 0 LRT CSDAVFs. Mean coil length occlusion was 432 cm for PT, 275 cm for RT, and 106 cm for LRT (P < 0.001). Immediate cure was achieved in 12 PT (57%), 23 RT (85%), and 20 LRT (95%) (P = 0.001). No major periprocedural complications were associated with any CSDAVFs. The mean duration of clinical follow-up was 17 months. CONCLUSIONS: Embolization outcomes may depend on the type of CSDAVF. The PT fistulas needed longer coils to achieve better angiographic outcomes. Some LRT fistulas may be difficult to access, and less coil utilization may lead to total fistula occlusion.

Therapeutic progress in pediatric intracranial dural arteriovenous shunts: A review.

Pediatric dural arteriovenous shunts (dAVSs) are a rare form of vascular disease: Fewer than 100 cases are reported in PubMed and the understanding of pediatric dAVS is limited. For this study, we searched in PubMed, reviewed and summarized the literature related to pediatric dAVSs. Our review revealed that pediatric dAVSs have an unfavorable natural history: If left untreated, the majority of pediatric dAVSs deteriorate. In a widely accepted classification scheme developed by Lasjaunias et al., pediatric dAVSs are divided into three types: Dural sinus malformation (DMS) with dAVS, infantile dAVS (IDAVS) and adult-type dAVS (ADAVS). In general, the clinical manifestations of dAVS can be summarized as having symptoms due to high-flow arteriovenous shunts, symptoms from retrograde venous drainage, symptoms from cavernous sinus involvement and hydrocephalus, among other signs and symptoms. The pediatric dAVSs may be identified with several imaging techniques; however, the gold standard is digital subtraction angiography (DSA), which indicates unique anatomical details and hemodynamic features. Effectively treating pediatric dAVS is difficult and the prognosis is often unsatisfactory. Transarterial embolization with liquid embolic agents and coils is the treatment of choice for the safe stabilization and/or improvement of the symptoms of pediatric dAVS. In some cases, transumbilical arterial and transvenous approaches have been effective, and surgical resection is also an effective alternative in some cases. Nevertheless, pediatric dAVS can have an unsatisfactory prognosis, even when timely and appropriate treatment is administered; however, with the development of embolization materials and techniques, the potential for improved treatments and prognoses is increasing.

[Intracranial dural arteriovenous fistulae. Experience after 81 cases and literature review]. / Fístulas durales arteriovenosas intracraneales. Experiencia con 81 casos y revisión de la literatura.

OBJECTIVES: To analyse the clinical, radiological and therapeutic variables of intracranial dural arteriovenous fistulae (DAVF) treated at our institution, and to assess the validity of the Borden and Cognard classifications and their correlation with the presenting symptoms. MATERIAL AND METHODS: The DAVF identified were retrospectively analysed. They were classified according to their location, drainage pattern and the Borden and Cognard classifications. We recorded the different treatments, their complications and efficacy. RESULTS: There were 81DAVF identified between 1975 and 2012. The cavernous sinus (CS) location was the most frequent one. The Borden and Cognard classifications showed an interobserver Kappa index of 0.72 and 0.76 respectively. The odds ratio of aggressive presentation in the presence of cortical venous drainage (CVD) was 19.3 (2.8-132.4). No location, once adjusted by venous drainage pattern, showed significant association with an aggressive presentation. Endovascular transarterial treatment of cavernous sinus DAVF achieved symptomatic improvement of 78%, with a complication rate of 5%. The DAVF of non-CS locations, with CVD, treated surgically were angiographically shown cured in 100% of the cases, with no treatment-related complications. CONCLUSIONS: The presence of CVD was significantly associated with aggressive presentations. The Borden and Cognard classifications showed little interobserver variability. Endovascular treatment for CS DAVF is safe and relatively effective. Surgical treatment of non-CS DAVF with CVD is safe, effective and the first choice treatment in our environment.

A new classification scheme for spinal vascular abnormalities based on angiographic features.

BACKGROUND AND PURPOSE: To determine the interobserver reliability of a newly proposed classification scheme for angiographic classification of spinal vascular malformations including arteriovenous fistulas (AVFs) and arteriovenous malformations (AVMs). METHOD: A study was performed done in which 1-2 representative angiographic images of 26 spinal AVFs and/or AVMs were independently classified by five fellows in the ACGME accredited Endovascular Surgical Neuroradiology (ESN) program and two external interventionalists in the absence of any other clinical or imaging data. From these observations the interobserver reliability for each category and the overall scheme were determined in terms of the median weighted kappa statistic. RESULTS: The overall interobserver reliability for the new classification scheme was a Kappa of 0.53 (Z = 21.3, P = <.0001) among the seven raters. The Kappa for individual grades was as follows: grade I (k = 0.66), grade II (k = 0.50), grade III (k = 0.44), and grade IV (k = 0.58). Three or more raters agreed on 100% of the cases. The interobserver reliability was high among the two practicing interventionalist raters (k = 0.55, 95% confidence interval 0.3-0.8). The interobserver reliability remained high among junior ESN fellows (k = 0.65). CONCLUSION: The new classification scheme provided satisfactory reliability even in the hands of less experienced observers. The scheme can be used with minimal training and other concurrent data and can be relied upon to provide consistent results.

Evaluating performance of the spetzler-martin supplemented model in selecting patients with brain arteriovenous malformation for surgery.

BACKGROUND AND PURPOSE: Our recently proposed point scoring model includes the widely-used Spetzler-Martin (SM)-5 variables, along with age, unruptured presentation, and diffuse border (SM-Supp). Here we evaluate the SM-Supp model performance compared with SM-5, SM-3, and Toronto prediction models using net reclassification index, which quantifies the correct movement in risk reclassification, and validate the model in an independent data set. METHODS: Bad outcome was defined as worsening between preoperative and final postoperative modified Rankin Scale score. Point scores for each model were used as predictors in logistic regression and predictions evaluated using net reclassification index at varying thresholds (10%-30%) and any threshold (continuous net reclassification index >0). Performance was validated in an independent data set (n=117). RESULTS: Net gain in risk reclassification was better using the SM-Supp model over a range of threshold values (net reclassification index=9%-25%) and significantly improved overall predictions for outcomes in the development data set, yielding a continuous net reclassification index of 64% versus SM-5, 67% versus SM-3, and 61% versus Toronto (all P<0.001). In the validation data set, the SM-Supp model again correctly reclassified a greater proportion of patients versus SM-5 (82%), SM-3 (85%), and Toronto models (69%). CONCLUSIONS: The SM-Supp model demonstrated better discrimination and risk reclassification than several existing models and should be considered for clinical practice to estimate surgical risk in patients with brain arteriovenous malformation.