Dural arteriovenous fistulas are abnormal connections of dural artery to dural veins or venous sinuses originating from within the dural leaflets. They are usually located near or within the wall of a dural venous sinus that is frequently obstructed or stenosed. The dural fistula sac is contained within the dural leaflets, and drainage can be via a dural sinus or retrograde through cortical veins (leptomeningeal drainage).
The natural history of cranial dural arteriovenous malformations (AVM's) is highly variable.
Awad et al., present their clinical experience with 17 dural AVM's in adults, including 10 cases with an aggressive neurological course (strictly defined as hemorrhage or progressive focal neurological deficit other than ophthalmoplegia). Two of these 10 patients died prior to surgical intervention and a third was severely disabled by intracerebral hemorrhage. Six patients underwent surgical resection of their dural AVM, with preparatory embolization in two cases. One patient received embolization and radiation therapy without surgery. Six of the seven cases without an aggressive neurological course were treated conservatively, and the seventh patient underwent embolization of a cavernous sinus dural AVM because of worsening ophthalmoplegia. In order to clarify features associated with aggressive behavior, a comprehensive meta-analysis was performed on 360 additional dural AVM's reported in the literature with sufficiently detailed clinical and angiographic information. The location and angiographic features of 100 aggressive cases were compared to those of 277 benign cases. No location of dural AVM's was immune from aggressive neurological behavior; however, an aggressive neurological course was least often associated with cases involving the transverse-sigmoid sinuses and cavernous sinus and most often associated with cases at the tentorial incisura. Contralateral contribution to arterial supply and rate of shunting (high vs. low flow) did not correlate with aggressive neurological behavior as defined. Leptomeningeal venous drainage, variceal or aneurysmal venous dilations, and galenic drainage correlated significantly (p less than 0.05) with aggressive neurological presentation. The latter three angiographic features often coexisted in the same dural AVM. It is concluded that these features significantly increase the natural risk of dural AVM's, and warrant a more vigilant therapeutic strategy 1).
Dural arteriovenous malformations in the anterior cranial fossa are rare and are especially prone to haemorrhage 2).
Cavernous sinus DAVFs are the most common site in the series of Signorelli et al. other locations in order of frequency are transverse-sigmoid sinus, tentorial, anterior cranial fossa, spinal and foramen magnum 3).
Dural arteriovenous fistulas can occur at any dural sinus but are found most frequently at the cavernous or transverse sinus.
Leptomeningeal venous drainage can lead to venous hypertension and intracranial hemorrhage.
The majority of patients presented with non-aggressive symptoms. 18% presented with intracranial hemorrhage: all the hemorrhages occurred in high-grade DAVFs 4).
Spontaneous closure of a dural arteriovenous fistula (dAVF) is a rare condition and only a few cases have been reported since its first description in 1976.
Only one report to document gradual closure of a dAVF by serial angiographic studies. The mechanism of spontaneous closure of dAVFs has not been fully elucidated 5).
The various treatment options include transarterial and transvenous embolization, stereotactic radiosurgery, and open surgery. Although many of the advances in dural arteriovenous fistula treatment have occurred in the endovascular arena, open microsurgical advances in the past decade have primarily been in the tools available to the surgeon. Improvements in microsurgical and skull base approaches have allowed surgeons to approach and obliterate fistulas with little or no retraction of the brain. Image-guided systems have also allowed better localization and more efficient approaches. A better understanding of the need to simply obliterate the venous drainage at the site of the fistula has eliminated the riskier resections of the past. Finally, the use of intraoperative angiography or indocyanine green videoangiography confirms the complete disconnection of fistula while the patient is still on the operating room table, preventing reoperation for residual fistulas 6).
For most patients, endovascular treatment, transarterial or transvenous, was the first option. Surgery was performed for the anterior cranial fossa DAVFs and other complex lesions draining mostly transverse-sigmoid sinus and tentorium. In 7% of cases a combination of endovascular + surgical treatment was used 7).
Dural arteriovenous fistula (AVF) presenting with subdural hematoma is relatively rare.
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).
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 8).
Ertl et al., aimed to perform a retrospective comparison of their primary success rates, complication rates, and long-term follow-up with those of sinus-occluding (SO) treatment variants in the collective of low- and intermediate-grade lateral DAVFs (Cognard Types I-IIb).
Clinical symptoms, complication rates, and Cognard grading prior to and after endovascular DAVF treatment using different technical approaches was retrospectively analyzed in 36 patients with lateral DAVF Cognard Types I-IIb. The long-term success rate was determined by a standardized questionnaire.
The SO approaches offered a higher rate of definitive fistula occlusion (93% SO vs 71% SP) but were accompanied by a significantly higher complication rate (33% or 20% SO vs 0% SP). The patients interviewed reported very high satisfaction with their health in long-term follow-up in both groups.
A higher rate of definitive fistula occlusion in the SO group was attained at the price of a significantly higher complication rate. The Sinus-preserving (SP) embolization approaches offered a good primary success rate in combination with a very low complication rate. Despite some limitations of the data (e.g., a small sample size) the authors thus recommend an SP variant as the primary therapeutic option for the endovascular treatment of low- and intermediate-grade DAVFs. The SO approaches should be restricted to cases in which SP treatment does not achieve a downgrading to no worse than Cognard Type IIa 9).
A 56-year-old man presented with disturbance of consciousness. Computed tomography demonstrated a right ASDH and a small right occipital subcortical hematoma. Cerebral angiography showed a dural AVF on the occipital convexity draining into the cortical veins. Emergent endovascular embolization was immediately performed and the shunt flow disappeared. Hematoma removal and external decompression were safely conducted. Combined therapy successfully recovered the patient's consciousness level. This rare case of dural AVF presenting with ASDH was treated with combined treatments of endovascular and open surgery 10).
A male patient who showed pure acute subdural hematoma aSDH and was diagnosed as having dural arteriovenous fistula AVF on the convexity near the superior sagittal sinus (SSS), based on angiographic findings. A 27-year-old man was admitted to the hospital due to headache with acute onset. The patient did not have a history of head trauma or injury. Head CT showed an abnormal high-density area on the surface of the cerebral hemisphere on the left side, indicating acute SDH. Angiography during the arterial phase demonstrated that an abnormal artery originating from the left occipital artery was connected with a dural vein and a diploic vein on the convexity near the SSS. They concude that a dural AVF existed at this area, and that the dural AVF had caused the acute SDH. Dural AVF/AVM which causes non-traumatic SDH is usually accompanied by intracerebral hemorrhage (ICH) and/or subarachnoid hemorrhage (SAH). In contrast, non-traumatic dural AVF/AVM presenting with pure SDH is rare, and this patient represents such a rare case. We should consider dural AVF/AVM and perform angiography if necessary when we encounter a patient showing non-traumatic SDH without ICH and/or SAH 11).
A patient presented with a sudden-onset severe headache, and was diagnosed with acute SDH by computed tomography. Cerebral angiography showed a DAVF on the left convexity adjacent to the superior sagittal sinus (SSS). This DAVF drained to the SSS and to the pterygoid venous plexus via the left middle fossa without retrograde flow (Type I according to the Cognard classification). The SDH was thickest at the lower convexity, which suggested that the draining vein of the DAVF was responsible for the bleeding.
The SDH slowly progressed for two weeks. The DAVF was successfully treated with transarterial embolization using N-butyl 2-cyanoacrylate. The SDH was resolved via burr-hole drainage surgery.
This is the first reported case of DAVF that caused non-traumatic progression to SDH. As DAVF can be the cause of acute and chronic SDH, cerebral angiography is recommended for non-traumatic acute SDH as well as for intractable chronic SDH 12).