Long-term treatment outcomes and natural course of low-grade intracranial dural arteriovenous fistulas

OBJECTIVE

In contrast to high-grade dural arteriovenous fistula (dAVF), low-grade dAVF is mainly associated with tinnitus and carries a low risk of morbidity and mortality. It remains unclear whether the benefits of active interventions outweigh the associated risk of complications in low-grade dAVF.

METHODS

The authors conducted a retrospective single-center study that included all consecutive patients diagnosed with an intracranial low-grade dAVF (Cognard type I and IIa) during 2012-2022 with DSA. The authors analyzed symptom relief, symptomatic angiographic cure, treatment-related complications, risk for intracerebral hemorrhage (ICH), and mortality. All patients were followed up until the end of 2022.

RESULTS

A total of 81 patients were diagnosed with a low-grade dAVF. Of these, 48 patients (59%) underwent treatment (all primary endovascular treatments), and 33 patients (41%) did not undergo treatment. Nine patients (19%) underwent retreatments. Angiographic follow-up was performed after median (IQR) 7.7 (6.1-24.1) months by means of DSA (mean 15.0, median 6.4 months, range 4.5-83.4 months) or MRA (mean 29.3, median 24.7 months, range 5.9-62.1 months). Symptom control was achieved in 98% of treated patients after final treatment. On final angiographic follow-up, 73% of patients had a completely occluded dAVF. There were 2 treatment-related complications resulting in 1 transient (2%) and 1 permanent (2%) neurological complication. One patient showed recurrence and progression of a completely occluded low-grade dAVF to an asymptomatic high-grade dAVF. No cases of ICH- or dAVF-related mortality were found in either treated patients (median [IQR] follow-up 5.1 [2.0-6.8] years) or untreated patients (median [IQR] follow-up 5.7 [3.2-9.0] years).

CONCLUSIONS

Treatment of low-grade dAVF provides a high rate of symptom relief with small risks for complications with neurological sequela. The risks of ICH and mortality in patients with untreated low-grade dAVF are minimal. Symptoms may not reveal high-grade recurrence, and radiological follow-up may be warranted in selected patients with treated low-grade dAVF. An optimal radiographic follow-up regimen should be developed by a future prospective multicenter registry.

Craniocervivcal Spinal Dural Arteriovenous Fistula Ligation via a Modified Suboccipital Craniectomy and C1 Laminectomy: Operative Video

Dural arteriovenous fistulas (dAVFs) are vascular malformations of the central nervous system that feature an arteriovenous shunt fed by dural arteries and can be intracranial or spinal.1-3 Spinal dAVFs are classically found at the nerve root sleeve.3 The arterial supply can often be predicted by the fistula location, whereas the symptomatology and risk of hemorrhage is determined by the venous drainage pattern.1-3 Craniocervical fistulas, a subset of dAVFs, may arise in association with the anterior condylar venous confluence or more dorsally in association with the transdural segment of the vertebral artery.1-3 This latter type of fistula typically has spinal venous drainage and may present with myelopathy from spinal cord venous congestion. We present a 61-year-old man who presented with a 2-week history of neck pain and paraparesis. Magnetic resonance imaging of the cervical spine revealed diffuse T2 hyperintensity of the cord from the pons to the level of the T1 vertebra. A computed tomography angiogram showed a possible dAVF at the craniocervical junction on the left. Because of the unclear nature of the patient's spinal cord lesion, a cerebral angiogram was performed. It confirmed a dAVF associated with the transdural segment of the left vertebral artery, with small dural feeders from the left vertebral artery and venous drainage into the anterior spinal vein. The patient underwent a modified suboccipital craniectomy and C1 laminectomy for dAVF ligation (Video 1). He was extubated postoperatively and discharged to a rehabilitation unit with improvement in lower extremity strength.

Access to cavernous dAVF via occluded superior petrosal Sinus

There are multiple treatment alternatives for cavernous dAVFs, with transvenous routes being most common. Among these routes, occluded inferior petrosal sinus is well-described, and, apart from being imaginative and elegant, it is also safe and effective. Herein we describe the application of this method to reach the fistulous pouch of a cavernous dAVF via an occluded superior petrosal sinus.

Spinal Dural Arteriovenous Fistulas: A Retrospective Analysis of Prognostic Factors and Long-Term Clinical Outcomes in the Light of the Recent Diagnostic and Technical Refinements

Spinal dural arteriovenous fistulas (dAVFs) are abnormal connections between the meningeal branches of segmental arteries and a radiculomedullary veins that result in a progressive myelopathy thanks to perimedullary coronal venous plexus congestion. Usually, dAVFs show nonspecific symptoms, thus leading to late clinical suspicion and a difficult MRI diagnosis.Several authors have tried to identify prognostic factors before treatment, but published studies results are often inconsistent and sometimes contradictory.In this study, we reviewed our recent experience of 30 dAVF patients where we collected all demographic, clinical and angioarchitectural features as well as radiological and treatment-related characteristics. The thoracic spine was the most common location, constituting 53.3% of cases, followed by the lumbar roots, comprising 30%. About 83% of patients showed motor deficits, urinary disturbances were present in 70%, and bowel symptoms in 50%.We treated 86.7% of patients with microsurgery and 13.3% with endovascular occlusion with a mean interval between clinical onset and intervention of 10.8 ± 14.2 months.A significant clinical improvement was observed at follow-up in 80% of patients, with a significant reduction in mean G-score, U-score and F-score at a mean follow-up of 105.89 ± 191.9 months.However, none among the principal demographic, clinical and radiological characteristics showed significant prognostic value to the clinical improvement observed at follow-up.

Dural arteriovenous fistulas misdiagnosed as intracranial neoplasms: illustrative case

BACKGROUND

Dural arteriovenous fistulas (dAVF) may induce imaging findings attributable to various disease entities including malignant neoplasms. In these cases, diagnosis and adequate treatment are often delayed and patients may be exposed to spurious treatments in addition to the risks inherent to an untreated dAVF with cortical venous drainage.

OBSERVATIONS

The authors report a case of a patient referred for surgical treatment of a supratentorial high-grade glioma. Thorough review of imaging data challenged the initial radiological diagnosis and led to proper angiographic workup. As a result, a high-grade dAVF was confirmed and successfully embolized. In addition to this case, we provide an extensive literature review on dAVF initially diagnosed as cerebral neoplasms, including clinical, imaging and follow-up data.

LESSONS

The literature provides diagnostic criteria for dAVF on magnetic resonance imaging; however, those criteria may be only partly applicable in many cases. Misdiagnosis of a neoplasm due to dAVF has been reported but remains rare, especially in supratentorial lesions. Digital subtraction angiography should be pursued to rule out an underlying vascular pathology if any doubt. This may prevent unnecessary interventions such as biopsies, pharmacological treatment and a delay in dAVF treatment, given its associated risk of hemorrhage and nonhemorrhagic neurological deficits.

Contemporary Management of Cranial Dural Arteriovenous Fistulas

Cranial dural arteriovenous fistulas (dAVFs) are rare acquired neurovascular disorders that have the potential to profoundly alter the local and global cerebral venous drainage. Factors such as location, angioarchitecture, degree of shunting, and mode of presentation all appear to have some bearing on the natural history of dAVFs, which can vary from almost entirely benign to life-threatening. Accurate and evidence-based risk stratification is, therefore, key to informing important management decisions. The treatment strategies are nuanced and, for an already rare entity, can vary tremendously from 1 fistula to another. It is only through a thorough understanding of their behavior and the treatment options available that we will be able to deliver tailored treatment to the correct dAVF and the correct patient. We aimed to provide an up-to-date summary of the reported data on the natural history and predictors of aggressive behavior for cranial dAVFs in general, followed by site-specific management considerations.

Asystole during Onyx embolization of 64-year-old patient with dural arteriovenous fistula

Asystole or bradycardia is a relatively uncommon side effect seen in patients undergoing endovascular embolization using dimethylsulfoxide based liquid embolic agents. We present a case of a patient who underwent dural arteriovenous fistula embolization and experienced bradycardia during Onyx injection but was stabilized and the procedure was completed successfully.

Simulation of superselective catheterization for cerebrovascular lesions using a virtual injection software

Background

This report addresses the feasibility of virtual injection software based on contrast-enhanced cone-beam CTs (CBCTs) in the context of cerebrovascular lesion embolization. Intracranial arteriovenous malformation (AVM), dural arteriovenous fistula (AVF) and mycotic aneurysm embolization cases with CBCTs performed between 2013 and 2020 were retrospectively reviewed. Cerebrovascular lesions were reviewed by 2 neurointerventionalists using a dedicated virtual injection software (EmboASSIST, GE Healthcare; Chicago, IL). Points of Interest (POIs) surrounding the vascular lesions were first identified. The software then automatically displayed POI-associated vascular traces from vessel roots to selected POIs. Vascular segments and reason for POI identification were recorded. Using 2D multiplanar reconstructions from CBCTs, the accuracy of vascular traces was assessed. Clinical utility metrics were recorded on a 3-point Likert scale from 1 (no benefit) to 3 (very beneficial).

Results

Nine cases (7 AVM, 1 AVF, 1 mycotic aneurysm) were reviewed, with 26 POIs selected. Three POIs were in 2nd order segments, 8 POIs in 3rd order segments and 15 POIs in 4th order segments of their respective arteries. The reviewers rated all 26 POI traces – involving a total of 90 vascular segments – as accurate. The average utility score across the 8 questions were 2.7 and 2.8 respectively from each reviewer, acknowledging the software’s potential benefit in cerebrovascular embolization procedural planning.

Conclusion

The operators considered CBCT-based virtual injection software clinically useful and accurate in guiding and planning cerebrovascular lesion embolization in this retrospective review. Future prospective studies in larger cohorts are warranted for validation of this modality.

Suboccipital, Supracerebellar, Infratentorial Approach for Microsurgical Clipping of a Ruptured Tentorial, Straight Sinus Type Dural Arteriovenous Fistula

BACKGROUND

Dural arteriovenous fistulas (dAVFs) can often be successfully treated with endovascular embolization; however, surgery is occasionally still required.

CASE DESCRIPTION

Herein, we discuss a 65-year-old male patient who presented with a Hunt-Hess IV subarachnoid hemorrhage, intraventricular hemorrhage, and cerebellar intracranial hemorrhage secondary to a ruptured Borden type III tentorial (straight sinus) dAVF. Angiography revealed supply from the left occipital and posterior meningeal arteries and direct drainage into the cerebellar cortical veins with venous aneurysms in both cerebellar hemispheres. Both transarterial and transvenous embolization were attempted, without success. Therefore, the patient was taken to the operating room for clip ligation of the dAVF. The operative video demonstrates a bilateral suboccipital craniotomy and supracerebellar infratentorial approach for surgical clipping of the dAVF.

CONCLUSIONS

The case and operative video provide a valuable addition to surgical literature in an era where surgical management of dAVFs has become relatively rare.

Microsurgery "Under the Eaves" Using ORBEYE: A Case of Dural Arteriovenous Fistula of the Anterior Cranial Fossa

BACKGROUND

One of the merits of exoscopes, including ORBEYE, is that they are superior to a microscope in terms of ergonomic features. We report a case of dural arteriovenous fistula (dAVF) that was cured by direct surgery using the ergonomic advantages of ORBEYE.

CASE DESCRIPTION

A 78-year-old man was found to have dAVF of the anterior cranial fossa incidentally. We performed direct surgery via bifrontal craniotomy. Because the frontal sinus was large, we reserved the frontal bone-like eaves in order not to open the frontal sinus. The vertex of his head was sufficiently down to shift the frontal lobe downward with gravity. During surgery, we set the angle of the operative visual axis of ORBEYE approximately horizontal to avoid the reserved frontal bone. We performed a stable operation using ORBEYE in a comfortable posture.

CONCLUSIONS

ORBEYE facilitates ergonomic microsurgery, even under the eaves, with the angle of the operative visual axis approximately horizontal using gravity.

Updates in the management of cranial dural arteriovenous fistula

Dural arteriovenous fistula (dAVF) accounts for approximately 10% of all intracranial vascular malformations. While they can be benign lesions, the presence of retrograde venous drainage and cortical venous reflux makes the natural course of these lesions aggressive high risk of haemorrhage, neurological injury and mortality. Endovascular treatment is often the first line of treatment for dAVF. Both transarterial and transvenous approaches are used to cure dAVF. The selection of treatment approach depends on the angioarchitecture of the dAVF, the location, the direction of venous flow. Surgery and, to a lesser extent, stereotactic radiosurgery are used when endovascular approaches are impossible or unsuccessful.

Reconsidering an important subclass of high-risk dural arteriovenous fistulas for stereotactic radiosurgery

OBJECTIVE

Aggressive dural arteriovenous fistulas (dAVFs) with cortical venous drainage (CVD) are known for their relatively high risk of recurrent neurological events or hemorrhage. However, recent natural history literature has indicated that nonaggressive dAVFs with CVD have a significantly lower prospective risk of hemorrhage. These nonaggressive dAVFs are typically diagnosed because of symptomatic headache, pulsatile tinnitus, or ocular symptoms, as in low-risk dAVFs. Therefore, the viability of stereotactic radiosurgery (SRS) as a treatment for this lesion subclass should be investigated.

METHODS

The authors evaluated their institutional experience with SRS for dAVFs with CVD for the period from 1991 to 2016, assessing angiographic outcomes and posttreatment hemorrhage rates. They subsequently pooled their results with those published in the literature and stratified the results based on the mode of clinical presentation.

RESULTS

In an institutional cohort of 42 dAVFs with CVD treated using SRS, there were no complications or hemorrhages after treatment in 19 patients with nonaggressive dAVFs, but there was 1 radiation-induced complication and 1 hemorrhage among the 23 patients with aggressive dAVFs. In pooling these cases with 155 additional cases from the literature, the authors found that the hemorrhage rate after SRS was significantly lower among the patients with nonaggressive dAVFs (0% vs 6.8%, p = 0.003). Similarly, the number of radiation-related complications was 0/124 in nonaggressive dAVF cases versus 6/73 in aggressive dAVF cases (p = 0.001). The annual rate of hemorrhage after SRS for aggressive fistulas was 3.0% over 164.5 patient-years, whereas none of the nonaggressive fistulas bled after radiosurgery over 279.4 patient-years of follow-up despite the presence of CVD.

CONCLUSIONS

Cortical venous drainage is thought to be a significant risk factor in all dAVFs. In the institutional experience described here, SRS proved to be a low-risk strategy associated with a very low risk of subsequent hemorrhage or radiation-related complications in nonaggressive dAVFs with CVD.

A multi-institutional analysis of the untreated course of cerebral dural arteriovenous fistulas

The authors attempted to better delineate the natural course of untreated cerebral dural arteriovenous fistulas. For a group of 295 fistulas, drainage pattern was most important in predicting the risk of future neurological events or bleeding. Moreover, presentation with a neurological event or hemorrhage was an independent risk factor for future neurological events or hemorrhage, respectively. The authors provided hemorrhage rates for various subclasses of dural arteriovenous fistulas to facilitate risk stratification, excluding partially treated lesions.

Surgical Disconnection of Posterior Fossa Right Tentorial Incisura Arteriovenous-Fistula Cognard IV

Posterior fossa dural arteriovenous fistulas are rare vascular malformations. If associated with cortical venous reflux, they present a significant risk of hemorrhage. We present a 54-year-old male who presented with progressive hearing loss without other neurologic symptoms. Further workup revealed tentorial incisura dural arteriovenous fistula with cortical venous reflux and aneurysmal dilation of venous drainage (type IV Cognard), fed from the right internal carotid artery and external carotid artery. After multidisciplinary discussion, we decided on surgical disconnection of the fistula as we felt this approach would have the highest chance of immediate and durable cure. We performed a right retrosigmoid craniotomy with (Video 1) disconnection of the arterialized veins and thus achieved completed obliteration. Follow-up angiography 8 months later showed no evidence of residual/recurrent fistula. The patient's hearing improved. There were no adverse effects during the perioperative period.

Subarachnoid Hemorrhage with Concurrent Dural and Perimedullary Arteriovenous Fistulas at Craniocervical Junction: Case Report and Literature Review

BACKGROUND

The association between a dural arteriovenous fistula (dAVF) and perimedullary arteriovenous fistula (AVF) is rarely observed at the craniocervical junction (CCJ). We present a case of subarachnoid hemorrhage (SAH) with concurrent dAVF and perimedullary AVF at the CCJ. Here, we describe the cause of bleeding and the process of determining whether it was a varix or an arterial aneurysm.

CASE DESCRIPTION

A 69-year-old man with SAH visited the emergency department. A dAVF at the CCJ was detected on digital subtraction angiography (DSA). However, after 3 weeks, when the DSA was repeated, a perimedullary AVF and varix were identified. We performed an endovascular treatment, but because the perimedullary AVF remained, we performed a direct surgery. The patient was discharged without weakness, but this left abducens nerve palsy remained.

CONCLUSIONS

In recent reports, SAH caused by concurrent dAVF and perimedullary AVF raised the possibility of an arterial aneurysm. However, in this case, the possibility of venous bleeding was high and a varix rather than an aneurysm was observed. On the basis of the reported cases, concurrent dAVF and perimedullary AVF at the CCJ is a "middle-flow arteriovenous shunt" that may induce a varix or an arterial aneurysm.

Asystole during onyx embolisation of a dural AV fistula: The trigeminocardiac reflex

There are fewer than 20 published case reports of bradycardia or asystole during intracranial embolisation procedures. These are well described in open neurosurgical procedures, particularly involving the skull base. We present a case of a 59-year-old male patient who presented for elective embolisation of a dural arteriovenous fistula. During the injection of Onyx, the patient experience sudden asystole, which recurred after a second Onyx injection. Following successful treatment, a third injection proceeded without incident.

Embolization of cranial dural arteriovenous fistulas in the liquid embolic era: A Sydney experience

Endovascular management of dural arteriovenous fistulas has become a mainstay of treatment. In particular, modern techniques have allowed greater fistula penetration and likelihood of complete obliteration. However, the efficacy of newer agents has not been quantified outside of predominantly small case reports and case series. Furthermore, the Australian experience with fistula embolization has yet to be reported in the literature. To this aim, we performed a retrospective review of our endovascular management of a large cohort of cranial dural arteriovenous fistulas in the liquid embolic era. This retrospective case series included ninety-six consecutive patients of any Cognard grade, treated between 2005 and 2016. Liquid embolic agents were used exclusively in eighty-three cases. The overall complete obliteration rate was 89.6% with a residual fistula rate of 2%, and complication rate of 8.3%. This Sydney, Australia cohort demonstrates excellent treatment effect and safety outcomes and thus supports the primary treatment of this condition by endovascular means.

Evolution of treatment and a detailed analysis of occlusion, recurrence, and clinical outcomes in an endovascular library of 260 dural arteriovenous fistulas

OBJECTIVE Many small series and technical reports chronicle the evolution of endovascular techniques for cranial dural arteriovenous fistulas (dAVFs) over the past 3 decades, but reports of large patient series are lacking. The authors provide a thorough analysis of clinical and angiographic outcomes across a large patient cohort. METHODS The authors reviewed their endovascular database from January 1996 to September 2015 to identify patients harboring cranial dAVFs who were treated initially with endovascular approaches. They extracted demographic, presentation, angiographic, detailed treatment, and long-term follow-up data, and they evaluated natural history, initial angiographic occlusion, complications, recurrence, and symptomatic resolution rates. RESULTS Across a cohort of 251 patients with 260 distinct dAVFs, the overall initial angiographic occlusion rate was 70%; recurrence or occult residual lesions were seen on subsequent angiography in 3% of cases. The overall complication rate was 8%, with permanent neurological complications occurring in 3% of cases. Among 102 patients with dAVFs without cortical venous reflux, rates of resolution/improvement of pulsatile tinnitus and ocular symptoms were 79% and 78%, respectively. Following the introduction of Onyx during the latter half of the study period, the number of treated dAVFs doubled; the initial angiographic occlusion rate increased significantly from 60% before the use of Onyx to 76% after (p = 0.01). In addition, during the latter period compared with the pre-Onyx period, the rate of dAVFs obliterated via a transarterial-only approach was significantly greater (43% vs 23%, p = 0.002), as was the number of dAVFs obliterated via a single arterial pedicle (29% vs 11%, p = 0.002). CONCLUSIONS Overall, in the Onyx era, the rate of initial angiographic occlusion was approximately 80%, as was the rate of meaningful clinical improvement in tinnitus and/or ocular symptoms after initial endovascular treatment of cranial dAVFs.

Clinical and Anatomic Insights From a Series of Ethmoidal Dural Arteriovenous Fistulas at Barrow Neurological Institute

BACKGROUND

Ethmoidal dural arteriovenous fistulas (dAVFs) have a malignant natural history and an anatomy that make endovascular therapy challenging. Their uniqueness begs for stratified analyses, but this has largely been precluded by their rarity. We sought to summarize the anatomic, presentation, treatment approaches, and clinical outcomes of patients with these lesions.

METHODS

We reviewed our prospectively maintained institutional database to identify patients diagnosed with ethmoidal dAVFs from January 1, 2000, to December 31, 2015. We evaluated demographic, presentation, angiographic, treatment, and follow-up data.

RESULTS

In total, 27 patients with ethmoidal dAVFs underwent endovascular and/or surgical treatment. Mean patient age was 62 years old and there was a male sex predilection (67% men; 2:1 male-female ratio). All dAVFs exhibited direct cortical venous drainage; venous ectasia was present in 59% of cases. Of the dAVFs, 30% drained posteriorly into the basal vein of Rosenthal or the sylvian veins. Embolization with casting of the draining vein was successful in 2 of 9 cases (22%), including 1 successful transvenous case. There were no clinical or permanent complications from embolization; specifically, no patients experienced visual loss after treatment. Surgical treatment with successful dAVF obliteration was carried out in 24 of 24 patients (100%). One patient declined surgical treatment after attempted endovascular embolization. There were no permanent complications after surgical treatment and no cases of wound infection or cerebrospinal fluid leakage.

CONCLUSIONS

Surgical disconnection remains the gold standard in the treatment of ethmoidal dAVFs. Embolization is a consideration for well-selected cases with favorable arterial or venous access anatomy.

Transarterial embolization of an anterior fossa cranial base dural arteriovenous fistula

Open surgical disconnection has long been the treatment of choice for dural arteriovenous fistulas (dAVFs) of the anterior cranial fossa. However, advanced patient age and the presence of medical comorbidities can substantially increase the risk of craniotomy and favor a less invasive endovascular approach. Optimal positioning within the distal ophthalmic artery, beyond the origin of the central retinal branch, is achievable using current microcatheter technology and embolic materials. Here we present the case of an 88-year-old female with an incidentally discovered dAVF of the anterior cranial fossa. Angiographic cure was achieved with one-stage Onyx embolization. The video can be found here: http://youtu.be/KVE0fUIECQM .

Balloon-assisted transarterial embolization of type 1 spinal dural arteriovenous fistula

Type 1 spinal dural arteriovenous fistula (dAVF) constitute the vast majority of all spinal vascular malformations. Here we present the case of a 71-year-old male with progressive myelopathy, lower-extremity weakness and numbness, and urinary incontinence. MRI imaging of the thoracic spine demonstrated cord edema, and catheter spinal angiography confirmed a type 1 spinal dAVF. The fistula was supplied by small dural branches of the left L-2 segmental artery. Angiographic cure was achieved with a one-stage procedure in which coils were used to occlude the distal segmental vessels, followed by balloon-assisted embolization with Onyx. The video can be found here: http://youtu.be/8aehJbueH0U .

Angiotensin-converting enzyme-inhibitors, statins and the risk of hemorrhage from cerebral dural arteriovenous fistulae

Leptomeningeal venous drainage and symptomatic presentation are known risk factors for cerebral dural arteriovenous fistula (dAVF) hemorrhage. An evaluation of potentially modifiable risk factors such as hypertension and medication usage has not been undertaken to our knowledge. The authors thus reviewed a cohort of 45 consecutive patients with cerebral dAVF with leptomeningeal venous drainage and compared the rate of hemorrhagic presentation for patients with and without a history of hypertension, hyperlipidemia or the usage of certain medications. Logistic regression was performed to determine the statistical significance of associations of each factor with hemorrhagic presentation. On univariate analysis, angiotensin-converting enzyme (ACE)-inhibitors (odds ratio [OR] 0.100, 95% confidence interval [CI] 0-0.764, p=0.024) and statins (OR 0.142, 95% CI 0.025-0.825, p=0.030) were associated with a statistically significant lower rate of hemorrhagic presentation. A trend toward a lower rate of hemorrhagic presentation was seen for patients taking aspirin (OR 0.153, 95% CI 0.016-1.43, p=0.10). These trends continued on multivariate analysis; however they did not meet statistical significance (p>0.05). Beta-blockers, calcium channel blockers, warfarin and selective serotonin reuptake inhibitors did not have a statistically significant association with the rate of hemorrhagic presentation (p>0.05). Although limited by small sample size, these results may suggest a beneficial effect of statins and ACE-inhibitors on the rate of dAVF hemorrhagic presentation, potentially as a result of anti-inflammatory, anti-angiogenic or even venous antithrombotic mechanisms. Despite this study's limitations, we hope it encourages further evaluation of potentially modifiable risk factors for vascular malformation hemorrhage.