Dealing with major vascular injury during endoscopic endonasal posterior fossa surgery can be fearsome and complex. This chapter gives an overview of the readiness, prevention, and surgical management of such instances.
Key wordsPosterior fossa – endoscopic endonasal surgery – vascular injury
11 Dealing with Major Vascular Injuries During Endonasal Posterior Fossa Surgery
11.1 Key Learning Points
Dealing with major vessel injury during endonasal posterior fossa surgery can prove more complex than with a parasellar internal carotid artery (ICA) injury.
Careful identification of high-risk cases helps prepare for a major vascular injury.
Adequate exposure helps to prevent and control major vessel injury during endoscopic endonasal surgery.
Applying pressure with a cottonoid on the site of bleeding is a good first step to gain initial control of the field and prepare for definitive control.
Options for obtaining definitive control over an injury depend on many factors including intradural or extradural localization.
Major vascular injury remains one of the most feared and dangerous complications in endoscopic endonasal surgery. Refinement of endoscopic endonasal surgery allowed expansion of these surgical approaches outside the sella. With new corridors and accessible anatomy came new risks, such as injury to major vascular structures other than the parasellar internal carotid arteries (ICAs). Major vascular injury to the posterior fossa can be particularly hazardous to manage endoscopically, due to the presence of perforators, highly eloquent neuronal tissue and nerves, and deep location. This chapter aims at providing an overview of the management of major vascular injury during endonasal posterior fossa surgery, with special attention to injury of paraclival ICAs, vertebrobasilar arteries, and their branches.
11.3 Preoperative Considerations
Being prepared to face a major vascular injury can make a significant difference in the outcome of said injury. The most important preoperative aspect resides in being able to recognize high-risk cases. 1 , 2 , 3 Proximity of the operated lesion to major vascular structures, ranging from simple contact to encasement and invasion, can significantly increase the risk of vascular injury and special attention should be paid to preoperative imaging (such as computed tomography [CT] angiogram) to assess the vascular relationships between the lesion and major vessels and anatomical variations. Previous surgery in the area can also increase vascular risk via scarring between the vessels and surrounding structures and also by giving the operator fewer anatomical landmarks to rely on during surgical approach. History of irradiation in the area can also heighten the risk of vascular injury via scarring and weakening of the vessel wall. Existing vascular conditions such as an aneurysm (or pseudoaneurysm) or visible vascular wall anomalies should also be considered significantly increased risk. All of those factors can be easily identified with careful examination of preoperative imaging and complete patient’s past medical history.
Related pathologies presenting a risk for major vessel injury during endoscopic endonasal surgery to the posterior fossa include craniopharyngiomas (which usually puts at risk the posterior communicating arteries and perforators), chordomas and chondrosarcomas (which put at risk the vertebrobasilar complex and the cavernous ICA—in case of infiltration of the cavernous sinus), petrous apex lesions such as cholesterol granulomas (which put at risk mainly the paraclival ICAs), clival meningiomas, and petroclival (controversial for endoscopic endonasal approach [EEA]) meningiomas (which put at risk the vertebral basilar complex).
If a procedure is deemed high risk, for example, a multioperated lesion with previous irradiation, the vascular risk should be weighted in the risk-benefit assessment and depending on circumstances the decision could be either to not operate, choose another treatment strategy (radiation instead of surgery), choose another surgical approach, or transfer the case to a highly experienced team. In cases of high risk of paraclival ICA injury, a useful preoperative adjunct is to perform a balloon test occlusion (BTO). This test can predict to a certain degree if sacrifice of the ICA will lead to a stroke. However, BTO should be done by an experienced endovascular team with rigorous criteria. BTO of the vertebral arteries can also be performed, although it is by far less often used. 4 It can be performed in those cases with very highly asymmetric vertebral arteries, when the dominant one is involved or in case of absence of communication between the contralateral vertebral artery and the vertebrobasilar junction. 5 , 6
Right before surgery for high-risk cases, the proper equipment (such as an adequate bipolar, endoscopic clips and single shaft clip appliers) should be available in the room and both the nursing team and anesthesiology team should be aware of the risk and should prepare accordingly by having blood products and extra suctions ready. In case of high risk of vascular injury, the neurointerventional team should also be aware and prepared. In the best scenario, the surgical team discuss in advance the possibility of a major vascular injury and a plan of action is already defined together with the neurointerventional team in the event of said injury.
11.4 Surgical Avoidance of Injury
The best way to manage major vascular injury in endoscopic endonasal surgery (EES) is to avoid them. A major aspect resides in localizing the high-risk vessel and working zone. Depending on various factors such as patient’s anatomy (e.g., sphenoid sinus pneumatization), tumor extent, and scarring, major vessels might be hard to visualize from the start. In these instances, relying on adjuncts such as image guidance (CT angiography, magnetic resonance imaging [MRI], and merged images) and Doppler ultrasound is paramount to help localize the vessels. These adjuncts, combined with in-depth study of preoperative imaging and careful, stepwise dissection technique, help minimize the risk of intraoperative injury.
Another important aspect is the degree of aggressiveness of lesion dissection from vessels. Depending on intrinsic factors such as tumor texture and vessel frailty, some small piece of tumor should be left on the vessel if its dissection is deemed too dangerous. Dissection of tumor from any vessel should be done as much as possible in a bimanual fashion using the same microsurgical principles as in open surgery in a clear field with maximal visualization of the vessel. One of the worst-case scenarios is a major vascular injury in the context of minimal access to it. To prevent this, potentially dangerous maneuvers on vessels should be performed once maximal safe exposure has been obtained, either through tumor resection and/or bony removal. The extent of exposure obtained should ideally allow for proximal and distal control of the involved vessel with aneurysm clips. When dealing with anterior circulation vessels, having paraclival carotids exposed for proximal control can prove useful. Ease of paraclival ICA exposure also greatly depends on the patient’s sinus pneumatization and has to be taken into consideration. Unfortunately, for posterior circulation vessels, early access to the vertebrobasilar might prove more arduous due to their inferior intradural localization. It is also important to remember that around a fragile vessel, almost any instrument has the potential to cause an injury and dissection should always be carried out with the utmost care. A pure diamond drill burr with continuous irrigation is recommended when removing bone over the cavernous ICA, and when using a Kerrison rongeur to remove the remaining thin shell of bone, care must be taken to be subperiosteal with the foot of the instrument and to constantly keep a close view of the side of the instruments while closing. Sharper instruments such as scissors and retractable blade pose a higher risk of injury, especially if not inserted under direct visualization. For dissection of the tumor away from the tumor or vessel away from the tumor, gentle repetitive strokes with a blunt suction will often be more than enough to safely resect tumor in contact with a vessel. For more adherent tumor, sharp dissection using a suction for counter-traction and scissors will also be useful, although bearing more risk for injury. Very gentle manipulation of calcified tumor lying next or around a major vessel without traction is mandatory in order to avoid direct vessel injury or avulsion of small collaterals embedded into the bloc (especially for highly calcified chondrosarcomas). Fig. 11.1 illustrates a case of an endoscopic endonasal removal of a clival chordoma adherent to the basilar artery and its branches, exemplifying the aforementioned principles.
11.5 Surgical Management
In the event of a major vascular injury, one of the first steps is letting everyone know it happened as fast and as clearly as possible. The anesthesiology team should expect intense and prolonged blood loss and act accordingly, scrub personnel directly assisting the surgeon should devote all of their attention to the procedure and instruments request, and circulating personnel should bring aneurysm clips if not already in the room. It is important to remember that an operator’s hasty and disorganized reaction to a major bleeding can sometimes cause more harm than the bleeding itself. In that regard, it is of upmost importance to remain as calm as possible. Adequate preparation and good communication with operating room personnel help to diminish the stress associated with such events. Help from another experienced surgeon, if available, should also be sought immediately. Having another operator can help to delegate the tasks, share the burden, and elaborate solutions. The additional surgeon can also drive the endoscope and bring cottonoid or hemostatic agent into the field while the operator is controlling the bleeding with tamponade and using his or her two hands. This can prove invaluable especially for less experienced surgeons.
11.5.1 Bleeding Localization and Control
Like in any bleed, the first step is to localize it. Bringing a cottonoid into the field and applying it with a suction at the site of the injury with enough pressure to stop the bleeding is a good way to do so. However, in case of intradural injury, pressure on the vessel should also be carefully applied in order not to damage the brainstem or cranial nerves behind it.
In case of a major bleeding, a significant volume of Surgicel, cottonoids, or other packing may have been applied for tamponade to control it. In this case it is more difficult to get perception of the amount of pressure on the surrounding structures which are hidden by the packing. These should be progressively taken out in order to locate the bleeding source and reapply the smallest possible Surgicel and/or cottonoid over it. Depending on the amount of bleeding, another surgeon holding/driving the endoscope and a second suction can be helpful to help take control of the field.
The “chopstick technique” used by the senior author can also be used and allows for bimanual manipulation with a single operator holding both the endoscope and the instruments. 7 One of the main advantages of the chopstick is to have no sword conflict with the endoscope and to allow for a very short distance between the tip of the endoscope and the tip of the instruments. The very close view of the tip of the instruments allows a precise control of the movements of the instruments and reduces the two-dimensional effect of the endoscope. The close view of the tip of the instruments also helps to reduce the risk of injury.
Once control is taken, this allows time to reassess the situation and surroundings. At that moment the following questions should be answered: Is the injury intradural or extradural? Can this vessel be safely sacrificed? What are the proximal and distal control options for the injured vessel?
Regardless of whether bleeding is of intradural or extradural origin, adequate visualization of the injured vessel is essential to help gain more definitive hemostasis. Although this can be challenging since the operator has to keep control over the bleeding while exposing the proximal and distal parts of the vessel, it should be attempted by either removing additional bone (e.g., exposing more proximal paraclival ICA), removing tumor, or dissecting arachnoid membranes. The goal is to visualize properly the site of injury and to have enough access proximally and distally to be able to occlude the vessel if needed. If potentially dangerous vessel dissection was kept for the end, this step is usually already done and proper visualization of the vessel and the injury is already obtained.
11.5.2 Extradural Bleeding
Major vascular injury management is different if it is present intradurally or extradurally. During EEA to the posterior fossa, the extradural vessels most at risk are the paraclival ICAs. The management of paraclival ICA injury follows the usual principles of ICA injury, which is the most commonly injured major vessel during EES and the injury on which the most literature has been written. 8 After gaining control of the field and proper exposure, a nonocclusive hemostatic method should be attempted. In cases of smaller injury, bipolar electrocautery on low setting can be attempted to close the vessel wall defect without occluding the vessel itself. The other preferred method is the application of a tangential clip to close the opening. During these attempts, significant blood loss should be expected and keeping contact with the anesthesiology team to ensure that resuscitation keeps up with the blood loss is paramount. To help visualize the defect, intravenous adenosine can be used to temporally arrest circulation. 9 Perfect coordination with the anesthesiology team is essential in order to arrest the flow only when the operator is ready to place the clip, maximizing the time during which the field will be free of blood.
If these maneuvers prove unsuccessful, local tamponade of the defect to stop the bleeding should be the next option. Sacrifice of the vessel should be considered only if a previous BTO was performed, confirming that sacrifice of the vessel is safe, or if no other option is available to control an ongoing bleeding putting the patient’s life at risk. Various materials have been reported for local tamponade, with cottonoid (gauze) being the most widely used, mainly because of its availability. 2 Other reported materials include Teflon, 10 crushed muscle, 11 , 12 , 13 Gelfoam, and oxidized cellulose. 13 , 14 , 15 One disadvantage of cottonoids is that they do not resorb and could promote infection if left in place. In that regard biocompatible and resorbable agents or autologous materials are better. Muscle has the advantages of good biocompatibility and crushing it could promote local blood clot formation via the release of calcium. 16 , 17 The main disadvantage of muscle resides in the fact that it must be harvested while keeping control over the injury. A possible tactic is to have one operator harvest the muscle as soon as the injury occurs while the others either compress the injury with a cottonoid or try other hemostatic methods. Muscle access should be anticipated during the preparation of the surgical field and draping. Common sites for muscle harvesting include the thigh and the temporalis muscle (which is closer to the nose). Regardless of the agent, the goal of local tamponade should be to stop the bleeding without occluding the vessel. 18 However, vessel occlusion is not uncommon and even sometimes unavoidable. 11 , 18 , 19
Other methods of vessel control have also been reported, such as the direct closure of the vessel using a Sundt-type clip. 18 A combination of the aforementioned techniques can also be used. For example, if a clip managed to significantly reduce the blood flow from the injury, adding some gentle local packing on the remaining bleeding might help to gain complete hemostasis.
If despite all of these maneuvers the bleeding is still ongoing, packing to control the bleeding as much as possible should be performed and emergent measures to bring the patient to the angiography suite to occlude the vessel should be taken. 14 , 20