Patient Positioning
- Based on DAVF location: Patient positioning depends on the DAVF’s location. For anterior fossa DAVFs, the supine position is routinely used. In cases of posterior circulation malformations, a prone, park bench or sitting position might be used.
- Head: The head should be secured with a head holder.
Surgical Approach
- Location of DAVF: Depending on location of the malformation different approaches can be used. Note that scalp and bony work could entail moderate to severe blood loss.
Intervention
- Preoperative endovascular obliteration: The current first-line treatment for cranial DAVFs is endovascular. Neurointerventional arterial obliteration might also be performed before open surgical approaches to decrease the flow through the fistula and to simplify the angioarchitecture of complex lesions prior to surgery. Nevertheless, arterial ligation alone cannot be considered curative. To achieve cure, the embolizing material must penetrate to the venous side of the malformation.
- Surgical occlusion of all arterial feeders to the fistula: This can be curative if all the feeders can be obliterated as they enter the fistula, as in the case of some tentorial AVFs.
Axial CT Posterior Fossa: A small hyperdense right paramedial cerebellar hematoma is seen on the head CT
Axial CT Tentorium: Subarachnoid hemorrhage is noted along the right tentorial edge
Right Internal Carotid Artery Angiogram, Lateral Projection, Early arterial Phase: The tentorial DAVF is fed mainly by meningo-hypophyseal trunk branches
Right Internal Carotid Artery Angiogram, Lateral Projection, Late Arterial Phase: A venous pouch next to the torcula-transverse sinus junction is seen
Right External Carotid Artery Angiogram, Lateral Projection: Contribution of the right occipital artery is noted
Right Internal Carotid Artery Angiogram, AP Projection, Early Arterial Phase: The fistulous connection of the meningo-hypophyseal trunk branches with the venous system is seen
Right Common Carotid Artery Angiogram, Lateral Projection: Postoperative changes are seen. There is no early venous drainage or arteriovenous shunting, confirming complete obliteration of the DAVF
- Interruption of the fistula via open dural or cortical vein ligation: This technique is especially suited for those fistulae where leptomeningeal venous reflux cannot be reached or it is considered dangerous (i.e. anterior fossa dural fistulae supplied by ophthalmic artery branches) through a neurointerventional approach. Disconnection of the arterialized vein (“red dilated veins”) should be performed as close as possible to the dural fistula using bipolar and microsurgery aneurysm clips (11,16,29). Hemoclips can be used with the disadvantage that they cannot be removed or repositioned. Caution must be paid to preserve veins and uninvolved segments of the sinuses that might contribute to anterograde normal flow of brain parenchyma. See video.
Axial CT Posterior Fossa: Lower cuts of the head CT without contrast showed pre-medullary subarachnoid blood
Axial CT Suprasella Cisterns, Sylvian and Interhemispheric Fissures: Subarachnoid blood extending to the Sylvian and interhemispheric fissures is seen. Higher concentration of blood is seen on the right side
Axial CT showing EVD Catheter: Due to the presence of acute hydrocephalus an external ventricular drain was inserted
Left Vertebral Artery, AP Projection, Arterial Phase: Antero-posterior projection. Early venous drainage towards the sellar/parasellar (paramedian and superiorly) region is noted
Left Vertebral Artery, Lateral Projection, Arterial Phase: A tortuous meningeal vessel arising from the initial V4 segment that runs medially and superiorly can be seen
Left Vertebral Artery, AP Projection, Arterial Phase: The patient underwent a suboccipital approach and ligation of the draining vein with complete obliteration of the malformation. No fistulous connection can be identified any longer
Left Vertebral Artery, Lateral Projection, Arterial Phase: Previously visualized early venous drainage running superiorly cannot be seen
- Skeletonization with or without sinus packing: The sinus can be skeletonized using high speed drill. If packing is necessary, it is usually achieved with a combination of muscle, cotton, Gelfoam, Floseal and Surgicel.
External Carotid Artery Injection, Arterial Phase: Angiogram showing a sagittal sinus fistula fed mainly by branches of the middle meningeal artery and also from the superficial temporal artery
Left Internal Carotid Artery, Arterial Phase: Early fistulous connection with the superior sagittal sinus is present
Left Internal Carotid Artery, AP View, Arterial Phase: Early cortical venous drainage is observed in the late arterial phase
Vertebral Artery Injection, Lateral Projection, Arterial Phase: Connection of posterior cerebral branches with the superior sagittal sinus fistulous point is noted
Vertebral Artery Injection, Lateral Projection, Capillary Phase: Massive early cortical venous drainage is present
Left External Carotid Artery Injection, Lateral Projection, Arterial Phase: A staged endovascular and surgical procedure was needed to obliterate this malformation. Packing of the superior sagittal sinus was performed. After multiple procedures, complete obliteration of the DAVF was achieved
Left Internal Carotid Artery Injection, AP Projection: After treatment the venous fistulous point at the superior sagittal sinus is no longer present.
Left Common Carotid Artery Injection, Lateral View, Arterial Phase: Post-treatment Left common carotid artery injection (lateral view). After treatment no contribution of any vessel to the previously noted DAVF is seen
Left Vertebral Artery Injection, Lateral Projection, Lateral View: After treatment previous branches of the posterior cerebral artery that were feeding the DAVF are no present
- Skeletonization and excision of the sinus: This is a more radical and definitive approach. It generally entails skull-base surgery techniques(8,15). However, this technique might be too aggressive in children due to the excessive blood loss associated with excision of the sinus and also because open draining vein interruption is generally successful.
- Confirm obliteration: Indocyanine green (ICG) video-angiography has recently been used as an intraoperative adjunct for DAVFs surgery for localization and confirmation of complete obliteration. An intraoperative angiogram might be also used with the advantage that several vessels can be injected, thus ruling out the presence of alternative feeders.
- “Access surgery”: In cases where arterial or venous access for endovascular treatment proves to be very challenging, direct exposure of the carotid(4) or venous sinuses can be performed to facilitate endovascular techniques.
Closure
- Substitutes: If large bony or dural defects are present, dural substitutes and bone substitutes with or without meshes can be used.
- Watertight: Posterior fossa dural closure should be watertight.
- Scalp: Routine closure techniques can be applied to the scalp.
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