11.1 Key Learning Points

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  Dealing with major vessel injury during endonasal posterior fossa surgery can prove more complex than with a parasellar internal carotid artery (ICA) injury.

  
  
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  Careful identification of high-risk cases helps prepare for a major vascular injury.

  
  
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  Adequate exposure helps to prevent and control major vessel injury during endoscopic endonasal surgery.

  
  
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  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.

  
  
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  Options for obtaining definitive control over an injury depend on many factors including intradural or extradural localization.

11.2 Introduction

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.

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