Dural arteriovenous fistula
|Dural arteriovenous fistula|
|This dural arteriovenous fistula of the superior sagittal sinus drains into subarachnoid veins and is classified as Borden type IIIb.|
|Classification and external resources|
A dural arteriovenous fistula (DAVF), is an abnormal direct connection (fistula) between a meningeal artery and a meningeal vein or dural venous sinus. In cases where there are multiple fistulas, the related term dural arteriovenous malformation (DAVF) is used.
- 1 Characteristics
- 2 Causes
- 3 Diagnosis
- 4 Treatment
- 5 Epidemiology
- 6 Research Directions
- 7 See also
- 8 References
- 9 External links
Signs and Symptoms
The most common signs/symptoms of DAVFs are:
Pulsatile tinnitus is the most common symptom in patients, and it is associated with transverse-sigmoid sinus DAVFs. Carotid-cavernous DAVFs, on the other hand, are more closely associated with pulsatile exophthalmos. DAVFs may also be asymptomatic (e.g. cavernous sinus DAVFs).
Most commonly found adjacent to dural sinuses in the following locations:
- Transverse (lateral) sinus, left-sided slightly more common than right
- From the posterior cavernous sinus, usually draining to the transverse or sigmoid sinuses
- Vertebral artery (posterior meningeal branch)
It is still unclear whether DAVFs are congenital or acquired. Current evidence supports transverse-sigmoid sinus junction dural malformations are acquired defects, occurring in response to thrombosis and collateral revascularization of a venous sinus.
Cerebral angiography is the diagnostic standard. MRIs are usually normal.
- Type I: dural arterial supply drains anterograde into venous sinus.
- Type II: dural arterial supply drains into venous sinus. High pressure in sinus results in both anterograde drainage and retrograde drainage via subarachnoid veins.
- Type III: dural arterial supply drains retrograde into subarachnoid veins.
Type I dural arteriovenous fistulas are supplied by meningeal arteries and drain into a meningeal vein or dural venous sinus. The flow within the draining vein or venous sinus is anterograde.
- Type Ia – simple dural arteriovenous fistulas have a single meningeal arterial supply
- Type Ib – more complex arteriovenous fistulas are supplied by multiple meningeal arteries
The distinction between Types Ia and Ib is somewhat specious as there is a rich system of meningeal arterial collaterals. Type I dural fistulas are often asymptomatic, do not have a high risk of bleeding and do not necessarily need to be treated.
The high pressure within a Type II dural AV fistula causes blood to flow in a retrograde fashion into subarachnoid veins which normally drain into the sinus. Typically this is because the sinus has outflow obstruction. Such draining veins form venous varices or aneurysms which can bleed. Type II fistulas need to be treated to prevent hemorrhage. The treatment may involve embolization of the draining sinus as well as clipping or embolization of the draining veins.
Type III dural AV fistulas drain directly into subarachnoid veins. These veins can form aneurysms and bleed. Type III dural fistulas need to be treated to prevent hemorrhage. Treatment can be as simple as clipping the draining vein at the site of the dural sinus. If treatment involves embolization, it will only typically be effective if the glue traverses the actual fistula and enters, at least slightly, the draining vein.
Cognard et al. Classification
The Cognard et al. Classification correlates venous drainage patterns with increasingly aggressive neurological clinical course.
|Classification||Location and clinical course|
|Type I||Confined to sinus wall, typically after thrombosis.|
|Type II||IIa - confined to sinus with reflux (retrograde) into sinus but not cortical veins.
IIb - drains into sinus with reflux (retrograde) into cortical veins (10-20% hemorrhage).
|Type III||Drains direct into cortical veins (not into sinus) drainage (40% hemorrhage).|
|Type IV||Drains direct into cortical veins (not into sinus) drainage with venous ectasia (65% hemorrhage).|
|Type V||Spinal perimedullary venous drainage, associated with progressive myelopathy.|
- Neurologic dysfunction or refractory symptoms
One approach used for treatment is embolization. A six-vessel angiogram is employed to determine the vascular supply to the fistula. Detachable coils, liquid embolic agents like NBCA, and onyx, or combinations of both are injected into the blood vessel to occlude the DAVF. Preoperative embolization can also be used to supplement surgery.
DAVFs are also managed surgically. The operative approach varies depending on the location of the lesion.
Stereotactic radiosurgery is used obliterating DAVFs post-embolization, and is considered an important adjunct. Use of this method, however, is limited to benign DAVFs that have failed other treatments.
10-15% of intracranial AV malformations are DAVFs. There is a higher preponderance in females (61-66%), and typically patients are in their fourth or fifth generation of life. DAVFs are rarer in children.
Manual carotid self compression is a controversial treatment for DAVF. Patients using this method are told to compress the carotid with the opposite hand for approximately 10 minutes daily, and gradually increasing the frequency and duration of compression. Currently, it is unclear whether this method is an effective therapy.
- Sundt, Thoralf M.; Piepgras, David G. (1983-07-01). "The surgical approach to arteriovenous malformations of the lateral and sigmoid dural sinuses". Journal of Neurosurgery. 59 (1): 32–39. doi:10.3171/jns.1983.59.1.0032. ISSN 0022-3085.
- Greenberg, Mark S. (2010-01-01). Handbook of neurosurgery. Greenberg Graphics. ISBN 1604063262. OCLC 892183792.
- Graeb, D. A.; Dolman, C. L. (1986-06-01). "Radiological and pathological aspects of dural arteriovenous fistulas. Case report". Journal of Neurosurgery. 64 (6): 962–967. doi:10.3171/jns.1986.64.6.0962. ISSN 0022-3085. PMID 3701446.
- "Transverse-Sigmoid Sinus Dural Arteriovenous Malformations. : Contemporary Neurosurgery". LWW.
- Rahul,, Jandial,; R.,, Aizenberg, Michele; Y.,, Chen, Mike. 100 case reviews in neurosurgery. ISBN 9780323356374. OCLC 966563367.
- Borden JA, Wu JK, Shucart WA (1995). "A proposed classification for spinal and cranial dural arteriovenous fistulous malformations and implications for treatment". J. Neurosurg. 82 (2): 166–79. doi:10.3171/jns.1995.82.2.0166. PMID 7815143.
- "jonathanborden-md.com". Retrieved 2007-12-22.
- Cognard C, Gobin YP, Pierot L; et al. (1995). "Cerebral dural arteriovenous fistulas: clinical and angiographic correlation with a revised classification of venous drainage". Radiology. 194 (3): 671–80. doi:10.1148/radiology.194.3.7862961.
- Carlson AP, Taylor CL, Yonas H (2007). "Treatment of dural arteriovenous fistula using ethylene vinyl alcohol (onyx) arterial embolization as the primary modality: short-term results". J. Neurosurg. 107 (6): 1120–5. doi:10.3171/JNS-07/12/1120. PMID 18077948.
- Barnwell, Stanley L.; Halbach, Van V.; Higashida, Randall T.; Hieshima, Grant; Wilson, Charles B. (1989-09-01). "Complex dural arteriovenous fistulas". Journal of Neurosurgery. 71 (3): 352–358. doi:10.3171/jns.1989.71.3.0352. ISSN 0022-3085.
- Lewis, Adam I.; Tomsick, Thomas A.; Tew, John M. (2009-05-28). "Management of tentorial dural arteriovenous malformations: transarterial embolization combined with stereotactic radiation or surgery". Collections. 15 (4): 851–859. doi:firstname.lastname@example.org.