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Although Onyx is approved as an embolic material for arteriovenous malformation (AVM) and dural arteriovenous fistula (dAVF), metal artifacts due to Onyx on CT remain problematic. We report the feasibility of a metal artifact reduction (MAR) algorithm on CT angiography (CTA) in the planning of direct surgery of dAVF after transarterial Onyx embolization. A 45-year-old male patient presented with right pulsatile tinnitus, and cerebral angiography demonstrated right tentorial dAVF. As the dAVF had not completely disappeared even after Onyx transarterial embolization, we planned direct surgery. Evaluation of the lesion was difficult on normal preoperative CTA because of Onyx artifacts, but CTA using MAR enabled a detailed planning of direct surgery. Direct surgery was performed through right retrosigmoid craniotomy. Referencing CTA using MAR, we identified the draining veins originating from the main drainer, which were coagulated and cut, achieving complete occlusion of the dAVF. His symptoms disappeared with no postoperative complications. CT angiography using MAR was useful for planning direct surgery after Onyx embolization. As the incidence of direct surgery after transarterial Onyx embolization for AVM or dAVF is increasing, MAR on CTA will become more important.

Arteriovenous malformations commonly present with hemorrhage, seizures, headache and other symptomatology. However, AVMs presenting as venous hypertension, owing to downstream stenosis/occlusion of venous sinuses, are very rare. This presentation is much more common in patients with dural AVFs.We present a young lady with left frontal arteriovenous malformation with bilateral transverse-sigmoid sinus stenosis, presenting with features of venous hypertension, which was treated with surgical excision of AVM. This case demonstrates a rare example of AVM with co-existing venous sinus stenosis distal to the nidus.High flow AVMs may co-exist with venous sinus stenosis or occlusion and lead to congestive venopathy. Treatment of AVM with surgical resection can be performed safely to relieve the hyper-dynamic venous congestion.

In recent years, with the current access in techniques, studies have significantly advanced the knowledge on meningeal immunity, revealing that the central nervous system (CNS) border acts as an immune landscape. The latest concept of meningeal immune system is a tertiary structure, which is a comprehensive overview of the meningeal immune system from macro to micro. We comprehensively reviewed recent advances in meningeal immunity, particularly the new understanding of the dural sinus and meningeal lymphatics. Moreover, based on the clues from the meningeal immunity, new insights were proposed into the dural arteriovenous fistula (DAVF) pathology, aiming to provide novel ideas for DAVF understanding.

Dural arteriovenous fistulas (DAVFs) are rare intracranial vascular malformations that present with a variety of clinical signs and symptoms. Among these, intracranial hemorrhage is a severe complication. A 72-year-old male presented with headache and pulsatile tinnitus. Cerebral angiography revealed a Borden II/Cognard IIa+b DAVF. He underwent stage 1 transarterial embolization of the occipital artery which reduced shunting by 30%. Several attempts were made to access the fistula during stage 2 transvenous embolization, but it was not possible to access the left transverse sinus fistula site since there was no communication across the torcula from the right transverse sinus and the left inferior sigmoid–jugular bulb was occluded. Therefore, a single burr hole was drilled and direct access to the DAVF was achieved with a micropuncture needle under neuronavigational guidance. The left transverse–sigmoid sinus junction was then embolized with coils. After the procedure, angiography revealed that the DAVF was cured with no residual shunting. This case demonstrates how minimally invasive surgery provides an alternative method to access a DVAF when conventional transarterial and/or transvenous embolization treatment options are not possible. Each DAVF case has unique anatomy and physiology, and creative multi-disciplinary strategies can often yield the best results.

Intracerebral hemorrhage is a devastating form of stroke and is more common in patients with hypertension and renal disease. We present the case of a lady suffering from chronic kidney disease who presented with severe headache and aphasia. On evaluation, she was found to have an intraparenchymal hemorrhage in the left temporal lobe with prominent pial and dural veins suggestive of a dural arteriovenous fistula (DAVF). Subsequently, she was detected to have occlusion of the left brachiocephalic vein (LBCV), which resulted in venous hypertension and resulted in this rare complication. Angioplasty followed by stenting of the LBCV resulted in subsidence of her symptoms. We wish to highlight this unusual but treatable complication of limb AV fistula which can mimic intracranial DAVF.

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.

A dural arteriovenous fistula (DAVF) is a dural-based shunt between meningeal arteries and meningeal veins, sinuses and/or cortical veins; they have been classified and named according to the location and the flow pattern. Petrous apex DAVFs are located where the petrosal vein penetrates the dura mater into the superior petrosal sinus; there are only few cases reported in the literature, they can show an aggressive behaviour (subarachnoid haemorrhage, severe brainstem oedema) with a high mortality rate. The described case is, to the best of our knowledge, the first case of a DAVF presenting with symptoms mimicking idiopathic normal pressure hydrocephalus. After worsening of gait impairment, memory loss and urinary incontinence an urgent CT of the brain showed hydrocephalus and a hyperdense mass in the pineal region mimicking a pineal tumour; an emergent digital subtraction angiogram showed a left petrous apex Borden type III DAVF. A transvenous embolisation was performed obtaining a complete obliteration.

Background Pipeline embolization device (PED) has proved its safety and efficacy in the treatment of intracranial large and giant side-wall aneurysms. With the accumulation of treatment experience, it is an inevitable trend to expand its off-label use on aneurysms. Whether flow diversion is safe and efficient in cases with special angioarchitecture has rarely been explored. Methods We performed a retrospective analysis of 210 consecutive patients treated by PED for intracerebral aneurysms in our center. Except for aneurysm, those patients also presented with special angioarchitecture: Fetal PCA, AVM, V-B junction and DAVF. Results Nine patients were qualified for the study. 1 was with fetal PCA, the aneurysm remained patent on 4-month follow-up. 2 with ipsilateral AVMs, one patient died due to brain hemorrhage 20 days after the operation, the other one was only partially embolised on 6 month follow up. 3 aneurysms located at V-B junction, angiographic follow up on 3 months demonstrated no complete occlusion of both the aneurysms, the other patients were still on follow up. All of the 3 cases with concomitant DAVF are completely occluded during short to midterm follow up. Conclusions PED for aneurysms incorporated the fetal PCA and V-B junction might meet a high propensity for incomplete occlusion during short term follow up. Aneurysm with ipsilateral AVM is not suitable for PED treatment due to the risk of hemorrhage and incomplete occlusion during midterm follow up. For aneurysm with concurrent DAVF, PED treatment is safe and efficient relatively in one session or by staged operation.

Spinal dural arteriovenous fistula (DAVF) occurs at any spinal level, but the clinical characteristics of lumbosacral DAVF have not been well documented. The purpose of this study was to evaluate clinical characteristics of lumbosacral DAVF and compare these features with those in thoracic DAVF.Twenty-five consecutive patients with 16 thoracic and 9 lumbosacral DAVFs were included (mean age, 63.9 years; 20 men). All patients presented with progressive myelopathy. Preoperative and postoperative neurologic deficits were compared between thoracic and lumbosacral DAVF groups. Using magnetic resonance imaging, the extent of T2 high-intensity areas and signal flow voids were documented. Follow-up after surgical interventions ranged from 6 to 96 months (mean, 38.1 months).Preoperatively, patients suffering lumbosacral DAVF tended to be more severely disabled compared with thoracic DAVF patients. Lumbosacral DAVF patients exhibited diminished patellar (P = 0.04) and Achilles tendon reflexes (P0.01), while most thoracic DAVF patients exhibited hyperreflexia. In magnetic resonance imaging, signal flow voids around the spinal cord were evident in only 4 of 9 lumbosacral DAVF patients (P = 0.012). Rather, a serpentine signal flow void of the filum terminale was a hallmark of lumbosacral DAVFs to distinguish them from thoracic DAVFs. In the lumbosacral DAVF group, postoperative improvements were significantly better in micturition function (P = 0.02).In lumbosacral DAVF, postoperative micturition function recovery was superior to thoracic DAVF. Intradural lumbar signal flow void is indicative of lumbosacral DAVF. For appropriate management, it is important to recognize these differences between lumbosacral and thoracic DAVF.

Dural arteriovenous fistula represents a rare cause of secondary Trigeminal Neuralgia. To date, there have been 18 reported cases of successful treatment of trigeminal neuralgia with endovascular embolization. Here we describe a unique case of a 51-year-old man with right-sided petrous ridge dural arteriovenous fistula causing ipsilateral V1 pain and cranial autonomic dysfunction. Cerebral angiography confirmed a Cognard type 3 right-sided tentorial dAVF supplied by an enlarged meningo-hypophpyseal vessel from the extradural ICA and by the middle meningeal artery. The fistula drains towards the midline via deep cerebral veins, the internal cerebral vein and the straight sinus with likely variceal compression of the right trigeminal nerve root entry zone. Transarterial Onyx embolization resulted in complete obliteration of the dural arteriovenous fistula with immediate resolution of facial pain and autonomic symptoms. After 24 months, the patient remains symptom-free and has no radiographic or clinical evidence of fistula recurrence. To date, there have been no other cases reported of trigeminal neuralgia with cranial autonomic symptoms or SUNCT syndrome due to a dural arteriovenous fistula. The presence of cranial autonomic symptoms with trigeminal neuralgia or a diagnosis of SUNCT should not deter endovascular treatments of dural arteriovenous fistulas or treatment of other compressive vascular lesions.

Dural arteriovenous fistulas (DAVFs) is a challenging condition in vascular neurosurgery. Development of new endovascular techniques has progressively modified treatment strategies; however, surgery is still considered a valid option of treatment of this pathology.From a retrospective analysis of our database, we selected 107 patients who underwent surgical treatment for DAVFs. Patients were grouped into five categories according to the Borden and Cognard classifications. Patients and treatment characteristics/outcome is reported.At admission, 30 (28 %) patients presented with intracranial hemorrhage. Fifteen (14 %) had seizure, whereas nearly half of the patients presented with non-aggressive symptoms, including headache (10, 9.3 %), cognitive impairment (8, 7.5 %), gait disturbance, and imbalance (8, 7.5 %). The majority of patients underwent surgical treatment of fistulas; in some cases, we elected combined surgical-endovascular (obliteration) treatment.Management of DAVF requires a multidisciplinary assessment and treatment strategies including surgical, endovascular, and radiosurgical treatment. The data reported confirmed that surgical treatment of DAVFs is associated with a good clinical and radiological (complete occlusion of the fistula) outcome in all cases, with a low rate of complications.

Type I and IIa dural arteriovenous fistulas (DAVFs) have a low hemorrhagic risk, but are often the cause of debilitating tinnitus that requires treatment. While Onyx® and PHIL™ (Precipitating hydrophobic injectable liquid) transarterial embolization represent the first endovascular option, there are occasional cases where performing angioplasty and stenting of the affected sinus may lead to satisfactory results. We retrospectively analyzed four consecutive cases of patients with DAVF-induced pulsatile tinnitus secondary to type I and II DAVFs who were treated with angioplasty and stenting of the sinus only. All the patients had clinical and radiological long-term follow-up. We noticed a significant radiological and clinical improvement in all the cases. Of the patients two were completely cured at follow-up with eradication of the neurological symptoms as well as the fistula, one was retreated with Onyx® for a very small residual shunt despite having no more tinnitus, and one showed improvement in venous drainage (from type IIa+b to type I fistula) without resolution of the fistula. In cases of type I and II DAVFs associated with sinus stenosis, angioplasty and stenting alone seem to be safe and effective. This treatment probably compresses the venules within the sinus walls, promoting thrombosis of the shunts thus solving the underlying cause of the fistula.

Caroticocavernous fistula or cavernous sinus dural arteriovenous fistula (CS-DAVF) has presented various treatment challenges over many years. This paper outlines these challenges in a review of the literature, and attempts to address them by analyzing the anatomical and hemodynamic characteristics of 32 consecutive patients with CS-DAVF treated between 2007 and 2016, in doing so proposing novel strategies for safe access and treatment of CS-DAVF.

The existing classification systems for dural arteriovenous fistula (DAVF) and cavernous sinus DAVF (CS-DAVF) are inadequate for modern practice. Neither of the widely used systems deals with the key morphological and hemodynamic properties of CS-DAVF. In this paper, a modification of the existing, generally used, classification system for DAVF is advanced to incorporate a more satisfactory description of CS-DAVF. Current classification1 and treatment of CS-DAVF is problematic. Most useful disease classifications permit understanding of the morphology of a disease or lesion, to gain insight into the natural history and/or prognosis of a particular disease/lesion, and/or to indicate the treatment options available for the lesion. The main classification system applied to CS-DAVF has been the Barrow classification1 (table 1), which describes at least two separate disease entities. View this table: Table 1 Barrow classification of CS-DAVF Barrow type A fistulae are lesions resulting from ruptured intracavernous aneurysms, spontaneous intracavernous carotid dissections, and traumatic carotid transection/dissection. Types B–D reflect a different disease entity and etiology from type A—that is, CS dural fistula. While types B–D reflect a single disease (DAVF), the stratification of lesions according to their internal carotid artery (ICA), external carotid artery (ECA) or ICA+ECA connections is arbitrary and conveys no information about the draining anatomy and hemodynamics of the lesion, both of which are relevant for the natural history, prognosis, and treatment. Incorporating aneurysmal/dissecting/traumatic caroticocavernous fistula into this classification is equally arbitrary in that the etiology, prognosis, and management of the condition may be completely different from types B–D. The Cognard classification of DAVF2 (table 2) deals with some of the morphological and hemodynamic features absent from the Barrow classification. View this table: Table 2 Cognard classification of dural arteriovenous fistula However, the location of the CS and its venous connections limit the utility of the Cognard classification in this location. For example, a CS-DAVF with …

LATAR BELAKANG:Cerebral venous sinus thrombosis (CVST) adalah penyakit yang jarang dikenali sehingga terlambat ditangani dan mengakibatkan komplikasi.1,2Dural arteriovenous fistula (DAVF) adalah fistula yang menghubungkan cabang arteri dural dengan vena dural. DAVF salah satu komplikasi pada kasus CVSTkronis, yang jarang ditemukan dan memiliki resiko tinggi terjadinya defisit neurologis maupun kematian.3Digital Subtraction Angiography (DSA) merupakan gold standard diagnosis fistula.3,4 Tujuan dari studi kasus ini untuk mengetahui komplikasi CVST dan penegakkan diagnosis dengan DSA.KASUS:Seorang wanita, usia 39 tahun dengan keluhan nyeri kepala kronis, pandangan mata kabur dan tinnitus telinga kiri selama 6 bulan. Pasien memiliki riwayat hipertensi dan penggunaan KB hormonal (pil esterogen). Pasien sadar penuh,disfungsi N II bilateral, motorik dan sensorik dalam batas normal. Pada pemeriksaan funduskopi didapatkan atrofi papil N II bilateral. Hasil Magnetic Resonance Imaging (MRI) didapatkan gambaran empty sella tursica, tak tampak infark, perdarahan maupun Space Occupying Lession(SOL) intrakranial. Hasil DSA menunjukkan trombus yang menyebabkan oklusi parsial pada sepertiga anterior Sinus Sagitalis Superior, Sinus Cavernosus kanan kiri, trombus yang menyebabkan oklusi total Sinus Sigmoideus kiri, dengandAVF intrakranial multipel, Cognard tipe I dan IIa. Pasien diterapi dengan antikoagulan (Class IIa;Level of Evidence B) dan diprogramkan embolisasi dAVF.KESIMPULAN:Cephalgia kronis, tinnitus dan disfungsi N II bilateral merupakan gejala klinis dari CVST.DAVF sebagai komplikasi CVST kronis ditegakkan melalui pemeriksaan DSA, yang harus segera ditindaklanjuti untuk mencegah perburukan klinis.Kata Kunci: cerebral venous sinus thrombosis, dural arteriovenous fistula, digital subtraction angiography

Background Tamoxifen is an estrogen-receptor modulator frequently used in the treatment of non-metastatic breast cancer. Side effects of this treatment are well evaluated but unproven side effects are suspected by case reports. Only one case report evokes a possible association between tamoxifen and dural arteriovenous fistula (dAVF). Authors report in this study their experience on dAVF in women exposed to tamoxifen. Methods From 2005 to 2015, 294 patients with a dural arteriovenous fistula were referred to our department. Among these cases, 10 women who harbored 12 dAVFs were under a treatment of tamoxifen at the time of the diagnosis of the dAVF or had a treatment of tamoxifen in the past. There is no exclusion criterion for this observational study. Results Ten women were included in this series (mean age: 64). Seven women were under treatment when the first symptom occurred and the three others had already finished their treatment. The mean delay between the initiation of tamoxifen and the occurrence of symptom was 32 months. The most frequent clinical symptom was a tinnitus (8 patients, 80%) followed by headache (3 cases, 30%), chemosis (2 cases, 20%), oculomotor palsy (2 patients, 20%), and ocular hypertension (1 case, 10%). One patient presented a cerebellar hemorrhage and arrived in a comatose state. The fistulous point was located in the transverse sinus (TS) in 9 cases (75%) and in the cavernous sinus in 3 cases (25%). Conclusions Our observational study suggests that the occurrence of cranial dAVF could be influenced by tamoxifen. It will be very difficult to establish a causal link between them but a larger comparative study could help.

Intracranial dural arteriovenous fistulas (dAVFs) often present with pulsatile tinnitus, orbital congestion, and headache. Occasionally, they present with focal neurologic deficits, a dementia-like syndrome, hemorrhage, or ischemic infarction. This study is based on the case of a 71-year-old gentleman who presented with 6 months of progressive forgetfulness, inattention, and hypersomnolence. Four weeks prior to presentation, he developed symptoms of left-sided pain, numbness, and worsening weakness. Neurologic examination demonstrated hypersomnolence, a score of 30/38 on the Kokmen Short Test of Mental Status, and left hemiparesis. MRI brain revealed bilateral thalamic T2 hyperintensities with associated enhancement. MR venogram (MRV) showed a vascular malformation in the posterior fossa and occlusion of the straight sinus. Conventional cerebral angiogram confirmed a tentorial dAVF. The dAVF was definitively treated with transarterial embolization, followed by clip ligation of the arterialized draining vein. Twelve weeks later, there was clinical resolution of left hemiparesis and improvement in cognitive status. MRI revealed complete resolution of the thalamic hyperintensities. MRV demonstrated recanalization of the straight sinus. Intracranial dAVFs are uncommon but potentially life-threatening acquired vascular malformations. The initiating factor is venous hypertension, causing retrograde flow, venous congestion, ischemia, and sometimes infarction. The spectrum of clinical manifestations in dAVFs reflects the degree of venous congestion present. If retrograde venous flow is surgically obliterated, then venous hypertension may be reversible. Bilateral thalamic venous congestion can present as a thalamic dementia. We conclude that intracranial dAVFs with thalamic venous congestion should be considered in the diagnostic differential for patients who present with subacute cognitive decline and T2 hyperintense thalamic signal change.

The precise mechanisms responsible for the development and growth of dural arteriovenous fistula (DAVF) remain unclear, but it has been hypothesized that vascular endothelial growth factor (VEGF) might be involved in the pathogenesis. The aim of this study was to examine the expression of VEGF in the rat DAVF model.Forty-five Sprague-Dawley rats were used in two experiments. In Experiment 1 (n = 20, including sham-operated controls), VEGF expression was analysed by Western blots in three different rat DAVF models: model I: common carotid artery-external jugular vein (CCA-EJV) anastomosis (n = 5); model II: sagittal sinus thrombosis and bipolar coagulation of the vein draining the transverse sinus (n = 5); model III: CCA-EJV anastomosis and bipolar coagulation of the vein draining the transverse sinus and sagittal sinus thrombosis to induce venous hypertension (n = 5). Based on the results of Experiment 1, Western blots were performed at weekly intervals 1, 2 and 3 weeks in Experiment 2 following induction of venous hypertension in model III (n = 5 at each time point and n = 5 sham controls); in addition, VEGF expression was immunohistochemically examined in the dura and the brain near the occluded sinus in five model III animals after 1 week.In Experiment 1, Western blot analysis showed barely detectable bands with molecular weights of 45 kD, corresponding to VEGF, in the sham group, but the highest level of VEGF was induced in model III, followed by models I and II (model IIImodel Imodel II). In Experiment 2, the expression of VEGF peaked 1 week after induction of venous hypertension in model III, decreasing in a linear fashion over 2 and 3 weeks (week 1weeks 2 and 3). The expression of immunoreactive VEGF was restricted in the connective tissue and the endothelial layer of the dura matter, cerebral cortical tissue and neurons of the basal ganglia.Our results strongly suggest a possible contribution of an angiogenic factor to the growth of DAVF. Venous ischemia by venous hypertension might be a mechanism for inducing up-regulation of angiogenic factor expression.

A 75-year-old woman with a dural arteriovenous fistula (DAVF) presented with progressive cognitive impairment including amnesia and alexia. Neuroradiological studies showed a relatively confined DAVF lesion in the left temporal lobe. The patient did not have a history of trauma and did not complain of headache or tinnitus. Amnesia and alexia dramatically improved upon treatment of the DAVF, and this was associated with attenuation of an abnormal MRI signal in the left temporal lobe. The results suggest that gradually impaired cerebral circulation due to focal venous hypertensive encephalopathy localized to the left temporal lobe and resulting from a DAVF could be involved in slowly progressive amnesia and alexia. The case also shows that an intracranial DAVF may present as a variety of neurological symptoms, depending on its localization, size and clinical stage.

Introduction Dural arteriovenous fistulas (DAVFs) is a challenging condition in vascular neurosurgery. Development of new endovascular techniques has progressively modified treatment strategies; however, surgery is still considered a valid option of treatment of this pathology.

Acquired arteriovenous malformations, such as is the case with dural arteriovenous fistulae (DAVF), are the consequence of a pathological new arterial ingrowth into venous spaces that reaches directly the venous lumen, without interposition of a capillary network, thereby creating an AV-shunt.The following concise text will provide elements in regards to diagnosis, indication for treatment discussion and choice of endovascular treatment (EVT) method.

Epidural skull base approach for dural arteriovenous fistulas (DAVF) of the anterior and middle cranial fossa

This paper reports that decompression of the facial nerve by transarterial Onyx embolization may relieve hemifacial spasm (HFS) caused by dilated veins due to a right petrosal dural arteriovenous fistula (DAVF). A 56-year-old man suffered severe chronic right HFS associated with a dilated right petrosal vein lying in the vicinity of the facial nerve. The right petrosal DAVF was reached through the middle meningeal artery using a transfemoral arterial approach and was occluded with Onyx 18 (M.T.I.- ev3, Irvine, CA, USA). There was complete remission of HFS without recurrence after two months of follow-up. This case supports vascular compression in the pathogenesis of HFS and suggests that facial nerve injury caused by a DAVF could be treated with transarterial Onyx embolization.

DSA is currently the criterion standard for the assessment of dural arteriovenous fistulas (dAVF). Recently, evolving MRA techniques have emerged as a non-invasive alternative. The aim of this study is to assess the value of 3 T MRI in detecting and describing dAVF and to determine whether MRI can replace DSA as diagnostic procedure. A total of 19 patients with dAVF and 19 without dAVF underwent the same MRI protocol, including 3D time-of-flight MRA and time-resolved contrast-enhanced MRA. The images were evaluated retrospectively by three independent readers with different levels of experience blinded to clinical information. The readers assessed the presence, the site, the venous drainage and the feeders of dAVF. Sensitivity, specificity, accuracy, intertechnique and interobserver agreements were calculated. DAVF can be detected with high sensitivity, specificity and accuracy by experienced and also by less experienced readers. However, MRI has limitations when used for grading and evaluation of the angioarchitecture of the dAVF. Different experience, the limited resolution of MRI and its inability to selectively display arteries were the reasons for these limitations. With MRI dAVF can be detected reliably. Nevertheless, at present MRI can not fully replace DSA, especially for treatment planning.

BACKGROUND AND PURPOSE: Cavernous sinuses and draining dural sinuses or veins are often visualized on 3D TOF MRA images in patients with dural arteriovenous fistulas involving the CS. Flow signals may be seen in the jugular vein and dural sinuses at the skull base on MRA images in healthy participants, however, because of reverse flow. Our purpose was to investigate the prevalence of flow signals in the pterygoid plexus and CS on 3T MRA images in a cohort of participants without DAVFs. MATERIALS AND METHODS: Two radiologists evaluated the flow signals of the PP and CS on 3T MRA images obtained from 406 consecutive participants by using a 5-point scale. In addition, the findings on 3T MRA images were compared with those on digital subtraction angiography images in an additional 171 participants who underwent both examinations. RESULTS: The radiologists identified 110 participants (27.1%; 108 left, 10 right, 8 bilateral) with evidence of flow signals in the PP alone (n = 67) or in both the PP and CS (n = 43). Flow signals were significantly more common in the left PP than in the right PP. In 171 patients who underwent both MRA and DSA, the MRA images showed flow signals in the PP with or without CS in 60 patients; no DAVFs were identified on DSA in any of these patients. CONCLUSIONS: Flow signals are frequently seen in the left PP on 3T MRA images in healthy participants. This finding may be the result of flow reversal and should not be considered to indicate occult DAVF.