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Far Lateral Craniotomy for Obliteration of High-Risk Craniocervical Junction Arteriovenous Fistula
Correspondence Address: Source of Support: None, Conflict of Interest: None DOI: 10.4103/0028-3886.333526
Keywords: Craniectomy, craniocervical junction, dural arteriovenous fistula, far lateral approach, vertebral artery
Dural arteriovenous fistulas (dAVF) are infrequent lesions that are reported to affect 5–10 people per million and account for less than 10% of all cerebral vascular malformations.[1],[2] Given this pathology involves both dural and meningeal layers, the clinical scenario is determined by the anatomical location. Generally, dAVFs located in the craniocervical junction can present with subarachnoid hemorrhage, progressive myelopathy, or brainstem ischemia. Endovascular therapy has advanced enormously in the past decade; however, even with the emerging technology, it is not uncommon that dAVFs located in the craniocervical junction require microsurgical treatment. The straight angle at which the feeding arteries often originate from the vertebral artery makes it very challenging to safely achieve distal selective catheterization. On the other hand, distal venous access is also frequently difficult given the small diameter and tortuosity of the venous system involved.[3],[4],[5] Therefore, microsurgical treatment with ligation remains an extremely important method and tool for managing this specific pathology.
This paper and the step-by-step surgical video are intended to demonstrate the far lateral approach for microsurgical ligation of craniocervical junction dAVFs to allow for optimal treatment of such disease worldwide.
A 60-year-old woman presented to our hospital after three episodes of severe right-sided occipitocervical headaches over the previous 2 weeks. She reported that the headaches were associated with bilateral arm and leg numbness and resolved on their own. Of note, the patient had a significant medical history of aortic valve replacement, emphysema, hyperlipidemia, hypertension, diabetes, gastroesophageal reflux, depression, and anxiety. Her medications of use at the time were aspirin (325 mg daily), insulin, a statin, and antihypertensive drugs. On physical examination, the patient was neurologically intact. Computed tomographic angiography (CTA) of the head and neck demonstrated an abnormal preponderance of vessels in the right craniocervical junction suggestive of a dural arteriovenous fistula (dAVF). A diagnostic cerebral angiography subsequently confirmed the diagnosis, localizing the fistulous connection at the V4 segment of the right vertebral artery between the origins of the right posterior inferior cerebellar artery (PICA) and the anterior spinal artery, with venous reflux anterior to the spinal cord and brainstem. After careful consideration with the patient and her family, it was decided to proceed with surgical treatment because of the risk of hemorrhage of the dAVF.
A right far lateral approach with lateral suboccipital craniectomy and C1 laminectomy was performed. Before disconnection of the fistula, a temporary aneurysm clip was applied to the draining vein immediately distal to the fistulous point, and an intraoperative indocyanine green (ICG) video angiogram was completed to show that the fistula no longer opacified, but the right PICA, anterior spinal artery, and right vertebral artery remained patent. Successful obliteration of the fistula was also confirmed with postoperative diagnostic cerebral angiography. Video link: https://youtu.be/bd9eMvmER8k QR Code:
Video timeline with audio transcript (minutes) 0.00.08: This video demonstration presents the case of a 60-year-old woman who presented with three episodes of severe right-sided occipitocervical headaches over the previous 2 weeks. These were associated with bilateral arm and leg numbness and resolved on their own. Her past medical history is as listed here, and she was on aspirin, insulin, statin, and antihypertensive drugs. 0.00.31: Her preoperative imaging demonstrated on the CTA a fistulous connection between the right V4 segment of the vertebral artery and a vein with venous reflux anterior to the spinal cord and brainstem. This was verified on the preoperative DSA. 0.00.55: The patient is placed in a lateral position, with the head held in a Mayfield head-holder, and we perform a far lateral approach to this right-sided V4 fistula. 0.01.09: The incision, as is outlined here, behind the mastoid and extends down into the anterior neck. The skin is opened and the muscles dissected down to the region of the suboccipital triangle muscles. The posterior arch of C1 and the vertebral artery are identified, and the muscular branches off the V3 segment are divided. We then free up the soft tissue investment off the vertebral artery in the V3 segment and identify the occipital condyle and the J groove of the hemiarch of C1. 0.02.02: A laminectomy is performed with the intent of opening up the exposure of the vertebral artery as it enters the dura. 0.02.18: Suboccipital craniectomy is performed and extended to the region of the occipital condyle. The posterior medial aspect of the condyle is removed, and the dura is exposed in the entrance of the vertebral artery into the dura. 0.02.45: We open up the dura just behind where the vertebral artery enters the dura and retract this back using suture. Intradurally, we can see the spinal accessory nerve and the proximal intradural vertebral artery and its branches. 0.03.14: We dissect and identify the region of the fistulous connection. Upon opening the arachnoid, we can see the fistulous connection emanating from the dura. The draining vein was then identified just anterior to the region of the varix. 0.03.52: We dissect out the draining vein and place a temporary clip over the draining vein to see if this effectively obliterates the fistula. ICG is performed, which demonstrates no further arteriovenous shunting. Thus, it is decided to remove the clip and formally ligate the fistulous connection. After the clip is removed, we dissect out the vein emanating from the varix, cauterize this, and divide it. 0.04.35: We then close the dura in a watertight fashion. We place a fat graft in the dead space from the approach, and vancomycin powder is included. We close the skin and the subcutaneous layers. 0.04.54: Postoperative angiogram shows no further fistulous connection. Her symptoms resolved after surgery and she was discharged home, intact neurologically, on postoperative day 4.
Postoperatively, the patient remained neurologically intact. She was discharged on postoperative day 4 without any complaints or complications. Pearls and pitfalls dAVF of the craniocervical junction is an infrequent pathology that can present clinically with myelopathy, brainstem ischemia, or subarachnoid hemorrhage. Treatment is warranted to prevent hemorrhage and ischemia and to eliminate and/or improve neurologic deficits from myelopathy. Microsurgical ligation remains the main method of treatment given the difficulty in accessing the region with an endovascular technique. The far lateral approach is an efficient way to tackle these lesions and provides a good surgical corridor. An ipsilateral hemilaminectomy of C1 and drilling of the medial aspect of the occipital condyle provide more room to better dissect and visualize the vertebral artery, providing better dural opening and more reliable intradural workspace. Opening of the duramater just behind the entry point of the vertebral artery provides good visualization of the vertebral artery throughout the entirety of the case and helps avoid unintended injury. Intraoperative ICG angiography after temporary clipping of the draining vein is an important tool that helps confirm the correct location of the fistulous connection and draining vein to proceed with ligation and disconnection accurately. Watertight closure of the dura mater is of fundamental importance given the high risk of CSF leak in skull base approaches. A fat graft is a valuable addition that minimizes dead space and helps seal the dural closure to help avoid cerebrospinal fluid leak and avoid a pseudomeningocele.[6] Postoperative angiography is recommended to confirm and document the complete resolution of the pathology.
dAVFs of the craniocervical junction often require microsurgical treatment because of the challenges of distal catheterization with an endovascular technique.[1],[2],[3],[6],[7] Therefore, mastery of how to effectively and safely treat this pathology surgically is of fundamental importance to the vascular neurosurgeon. The far lateral approach arguably offers the safest and most efficacious corridor in which to work to correct this disease through microsurgical ligation and disconnection.[7] Care must be taken to avoid injury to the vertebral artery at its V3 and V4 segments as it runs through C1 and enters the dura mater. Localizing the entry point of the vertebral artery in the dura mater is also important to perform the dural opening vertically just anterior to that point. That way, the vertebral artery is always very well visualized, either intra or extradural, facilitating avoidance of any injury to it. With the most common complication of this approach being cerebrospinal fluid leak, it is important to obtain watertight dural closure.[7] In cases in which a watertight primary dural closure cannot be obtained, a dural substitute can be used or even a muscular or fascia graft. An additional fat with or without fascia graft is also an option that can further seal the dead space and better prevent an unwanted cerebrospinal fluid leak and the development of pseudomeningocele.[6] Intraoperative ICG angiography is an extremely important tool that can verify the correct location of the fistulous connection, and it should be used routinely in such cases when possible. However, a postoperative diagnostic angiogram is also warranted to confirm and document the complete resolution of the pathology. Symptomatology often improves in the early postoperative period, but it may vary depending on the severity of preoperative neurological deficits. Mastery of the far lateral approach and its nuances as well as pitfalls and avoidance of possible complications and technical aspects of microsurgical ligation and disconnection of the fistulous point is of substantial importance for vascular neurosurgeons, who will undoubtedly encounter craniocervical junction dAVFs in their practice.
This case demonstrates that microsurgical ligation and disconnection of craniocervical dAVF is safely and efficiently obtained through a far lateral approach and remains an important art to master for vascular neurosurgeons who are faced with this pathology on a regular basis. Acknowledgements We thank Vance Mortimer for assistance with preparing the video and Kristin Kraus for editorial assistance. Declaration of patient consent Full and detailed consent from the patient/guardian has been taken. The patient's identity has been adequately anonymized. If anything related to the patient's identity is shown, adequate consent has been taken from the patient/relative/guardian. The journal will not be responsible for any medico-legal issues arising out of issues related to the patient's identity or any other issues arising from the public display of the video. Financial support and sponsorship Nil. Conflicts of interest There are no conflicts of interest.
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