Injury of the internal carotid artery during endoscopic endonasal skull base surgery is a feared and perilous scenario. This article discusses perioperative strategies to prevent or manage an internal carotid artery injury to optimize outcomes. Meticulous preoperative planning is crucial in preventing its occurrence and minimizing its consequences. An effective plan of action relies on a well-prepared protocol, availability of proper instruments and devices, and an experienced multidisciplinary team. Intraoperative control of hemorrhage and stabilization of the patient’s cardiovascular status is followed by an angiography and endovascular treatment whenever possible. Close clinical and radiologic monitoring of the patient prevents early and late complications.
Key points
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Preoperative planning and the identification of potential risk factors are crucial in preventing an internal carotid artery injury and minimizing its consequences.
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An effective plan of action during the catastrophe relies on a previously established protocol, availability of proper instruments and devices, and an experienced multidisciplinary team.
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Intraoperative hemostasis should be followed by an angiography and endovascular treatment whenever possible.
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Close clinical and radiologic monitoring is important to prevent early and late complications.
Introduction
Skull base surgery has undergone a remarkable metamorphosis over the past two decades, precipitated in great part by the introduction of the extended endonasal approaches (EEA). Endoscopic endonasal techniques represent just one component of a larger philosophic and technical shift toward minimally invasive and minimal access strategies to reduce some of the risks and complications associated with traditional open skull base surgery. However, despite the fact that EEAs are effective and less invasive than traditional techniques, some surgeons consider that the risk of injury and inability to control, or repair, a major vascular injury is a significant surgical limitation of the technique. Although this statement is controversial and refutable for properly selected cases, the need to expose and manipulate the internal carotid artery (ICA) within the operative field, irrespective of the approach, often dictates the extent of the surgery and may even force the surgeon to abort the surgical procedure, deeming the tumor “unresectable.” Therefore, the relationship of the ICA to the surgical corridor and the target lesion is an important consideration that affects the entire perioperative planning.
Rather than a rare event, encountering the ICA in one form or another is extremely common during endoscopic endonasal skull base surgery. The lateral wall of the sphenoid sinus has an intimate relationship with the ICA and a transphenoidal route is the keystone of most EEAs. A bulging ICA and dehiscence of its bony canal are found respectively in 70% and 22% of patients, therefore compounding the difficulty of a wide range of sinonasal and skull base surgeries. In addition, multiple clinical situations, including the management of advanced sinonasal, middle, and posterior cranial fossa lesions, may require exposure and mobilization of the ICA. Furthermore, lesions within the petrous apex, cavernous sinus, infratemporal fossa, and parapharyngeal space require the identification of pertinent segments of ICA as a critical step.
Injury to the ICA and the resultant bleeding may lead to catastrophic complications that include permanent disabilities and death. Therefore, the prevention and management of such an injury is of paramount importance. The incidence of accidental injury of the ICA during traditional skull base surgery ranges from 3% to 8%. Although the rate of ICA injury during endoscopic sinus surgery is rare (<1%) and has been documented mostly as case reports, the incidence during EEAs is 10-fold higher. EEAs need a wide exposure and aim for more extensive resection; thus, it is logical that they are associated with a higher incidence (4%–9%) of ICA injury. Nonetheless, a review of the literature suggests that its incidence is rare, being reported mostly as part of retrospective studies and case reports. One must consider, however, that the incidence of this challenging surgical scenario is likely to be underestimated because many cases are not reported or the calculation of its incidence may include cases that are not at risk (eg, lesions in the anterior skull base).
There is scant literature regarding the comprehensive management of an ICA injury and hemorrhage. This article provides a panorama including a discussion of risk factors that help to recognize those patients at risk for an ICA injury, strategies to prevent the injury, and perioperative management strategies to yield the best possible outcome in case the ICA is injured. Suggested is a plan of action based on the available literature and the authors’ experience. The discussion pivots around the management of bleeding from an accidental ICA injury during an EEA, where two surgeons are involved; however, the expounded principles are applicable to other clinical scenarios.
Introduction
Skull base surgery has undergone a remarkable metamorphosis over the past two decades, precipitated in great part by the introduction of the extended endonasal approaches (EEA). Endoscopic endonasal techniques represent just one component of a larger philosophic and technical shift toward minimally invasive and minimal access strategies to reduce some of the risks and complications associated with traditional open skull base surgery. However, despite the fact that EEAs are effective and less invasive than traditional techniques, some surgeons consider that the risk of injury and inability to control, or repair, a major vascular injury is a significant surgical limitation of the technique. Although this statement is controversial and refutable for properly selected cases, the need to expose and manipulate the internal carotid artery (ICA) within the operative field, irrespective of the approach, often dictates the extent of the surgery and may even force the surgeon to abort the surgical procedure, deeming the tumor “unresectable.” Therefore, the relationship of the ICA to the surgical corridor and the target lesion is an important consideration that affects the entire perioperative planning.
Rather than a rare event, encountering the ICA in one form or another is extremely common during endoscopic endonasal skull base surgery. The lateral wall of the sphenoid sinus has an intimate relationship with the ICA and a transphenoidal route is the keystone of most EEAs. A bulging ICA and dehiscence of its bony canal are found respectively in 70% and 22% of patients, therefore compounding the difficulty of a wide range of sinonasal and skull base surgeries. In addition, multiple clinical situations, including the management of advanced sinonasal, middle, and posterior cranial fossa lesions, may require exposure and mobilization of the ICA. Furthermore, lesions within the petrous apex, cavernous sinus, infratemporal fossa, and parapharyngeal space require the identification of pertinent segments of ICA as a critical step.
Injury to the ICA and the resultant bleeding may lead to catastrophic complications that include permanent disabilities and death. Therefore, the prevention and management of such an injury is of paramount importance. The incidence of accidental injury of the ICA during traditional skull base surgery ranges from 3% to 8%. Although the rate of ICA injury during endoscopic sinus surgery is rare (<1%) and has been documented mostly as case reports, the incidence during EEAs is 10-fold higher. EEAs need a wide exposure and aim for more extensive resection; thus, it is logical that they are associated with a higher incidence (4%–9%) of ICA injury. Nonetheless, a review of the literature suggests that its incidence is rare, being reported mostly as part of retrospective studies and case reports. One must consider, however, that the incidence of this challenging surgical scenario is likely to be underestimated because many cases are not reported or the calculation of its incidence may include cases that are not at risk (eg, lesions in the anterior skull base).
There is scant literature regarding the comprehensive management of an ICA injury and hemorrhage. This article provides a panorama including a discussion of risk factors that help to recognize those patients at risk for an ICA injury, strategies to prevent the injury, and perioperative management strategies to yield the best possible outcome in case the ICA is injured. Suggested is a plan of action based on the available literature and the authors’ experience. The discussion pivots around the management of bleeding from an accidental ICA injury during an EEA, where two surgeons are involved; however, the expounded principles are applicable to other clinical scenarios.
Risk factors
Prevention is best; therefore, each clinical scenario and specific patient circumstances should be appraised during the perioperative period. Preoperative identification of risk factors is paramount to avoid or minimize the risk of ICA injury, to establish a surgical plan in case the vessel is injured intraoperatively, and to consider postoperative strategies that decrease the risk of morbidities related to the vascular accident or its treatment. Risk factors may be cataloged into anatomy related, pathology related, surgeon related, or institution related ( Table 1 ). However, one should consider that multiple factors are usually in play during any major surgical complication. A catastrophic complication is rarely the result of an isolated circumstance.
| Category | Factors |
|---|---|
| Anatomy-related | Dehiscent ICA canal Sphenoid septa with attachments to the ICA canals Short distance between ICAs Vessel wall abnormalities ICA displacement by the lesion |
| Pathology-related | Adherence of the lesion to ICA Previous extended surgery Previous radiotherapy Previous bromocriptine therapy |
| Skills and resource-related | Inexperience in skull base surgery Lack of adequate instruments and equipment |
| High-risk | Radical resection of an adherent lesion Encasement of ICA Need for wide exposure (≥2 segments of ICA) |
Anatomic Risks
The anatomic relationship between the ICA and the sphenoid sinus has been extensively described. Dehiscent bone over the ICA is found in 4% to 22% of anatomic specimens. Therefore, an incomplete bony cover or the presence of very thin bone over the ICA should be presumed and the mucoperiosteum and bone over the ICA should be dissected with care. Similarly, bulging of the ICA within the sphenoid sinus has been noted in 8% to 70% of patients. This variation and its frequency are subject to the degree of sinus pneumatization. Similarly, the average distance between the cavernous segments of the ICAs is 12 mm; however, it can be less than 4 mm. A close distance between the ICAs places both vessels at risk during the surgical exposure. Furthermore, intersinus septations commonly attach to the internal carotid and optic nerve canals. Bony septations need to be removed gently, avoiding aggressive manipulation that could result in fracturing a septum attached to the ICA canal, thus creating torsion or a sharp edge with a subsequent vascular injury. Strong septations that are resistant to true-cut forceps or rongeurs are best removed using a high-speed drill with coarse or hybrid diamond burrs.
Vascular abnormalities contribute directly to the incidence of ICA injury with subsequent catastrophic perioperative bleeding. Presence of aneurysms, pseudoaneurysms, or carotid-cavernous fistulae has been reported as a contributing factor for inadvertent internal carotid injury. Noticeably, around 10.6% of all intracranial aneurysms are located in the cavernous segment of the ICA.
Ectasia or displacement of the ICA by a tumor may place the vessel at risk by shifting its position into the path of the surgical corridor. Relatively common clinical scenarios include the presence of an ectatic ICA posterior to the median nasopharynx in a patient requiring a transodontoid approach and the anterior displacement of the petrous and paraclival segments in patients with chondrosarcoma.
Pathology-Related Risks
Tumors in intimate contact with the ICA could obscure or obliterate the plane of dissection leading to a devastating injury of the vessel during their resection. In general, the probability of a tumor invading the ICA wall, and consequently leading to a surgical injury during the tumor dissection, is proportional to the degree of tumor encirclement and its adherence to the vessel. Encirclement of the vessel is ascertained with preoperative imaging, whereas adherence could be hard to predict (it should be expected in previously operated or irradiated patients). Tumor histology may contribute to the risk of a transmural injury through the degree of invasiveness and infiltration of the ICA wall. Gardner and colleagues suggested that chondroid tumors (chordomas and chondrosarcomas) harbor a higher risk for ICA rupture than other pathologies because of the need for greater exposure of multiple segments of ICA and displacement of the vessel out of the anatomic position. We believe that these tumors may destroy the periosteum that normally protects the cavernous sinus and petrous segments of the ICA, thus making it more vulnerable to surgical trauma.
Previous surgery, previous external radiotherapy (risk may be higher after proton or stereotactic radiation), or chemoradiotherapy, and prior treatment with bromocriptine for pituitary tumors also have been linked to ICA injury. Increased fibrosis, adhesions, and loss of the surgical landmarks could explain this relationship. Raymond and colleagues found that 30% of patients who suffered an ICA injury have had prior bromocriptine therapy, 30% were revision cases, and 23% had previous radiation therapy.
The site of origin and extension of the lesion also play a significant role in the surgical threat to the ICA. Endoscopic sinus surgery and endoscopic approaches to the anterior cranial fossa carry a meager risk of injuring the ICA. Conversely, middle and posterior cranial fossa approaches carry a considerable risk because the course of ICA is closely related to the surgical corridor and area of resection.
Skills and Resource-Related Risks
Advanced endoscopic endonasal skull base surgery requires a highly qualified team with reasonable experience in managing vascular challenges and reconstructive techniques. Similarly, using inappropriate instrumentation during exposure or dissection of the ICA could lead to an accidental injury. A variety of manual and powered instrumentation including (but not excluding others) rongeurs, forceps, drills (coupled with cutting or aggressive burrs), microdebriders, ultrasonic aspirators, and monopolar electrocautery (blade, needle, or suction tipped) have been implicated in various ICA injuries. In general, powered instruments are best avoided during a dissection close to the ICA, with the exception of high-speed drills that are required to remove bone around the vessel. In addition, dealing with complex or high-risk cases in insufficiently equipped institutions is unwise (eg, no intensive care unit, no endovascular neurosurgeon or interventional radiologist).
High-Risk Factors
As a whole, the previously mentioned problems and concerns are relative factors and any single issue is rarely the culprit of an accidental injury. The likelihood of vascular injury increases exponentially with the amalgamation of multiple risks. For example, the authors consider the following scenarios as high-risk factors:
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Radical resection with curative intent for lesions that are adherent to the carotid wall.
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Tumors encircling the ICA greater than 120°.
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Lesions that require wide exposure of the carotid (ie, exposing one or more segments of the carotid or mobilization of the ICA).
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Previously irradiated lesions that are attached to the ICA (especially if proton, neutron, or intensified radiotherapy regimens have been used).
Identifying patients at risk helps in patient’s counseling, preoperative work-up, appropriate multispecialty consultation, intraoperative preparation, and postoperative follow-up. Furthermore, these patients may require preemptive surgical or endovascular control of the ICA.
Preoperative work-up
Advanced endoscopic endonasal skull base surgery should be performed in a multidisciplinary environment that provides adequate resources to attend to this complex clinical scenario. The surgical plan must be discussed among the members of the core team, consisting of a skull base otolaryngologist (ie, rhinologist or head and neck surgeon), a skull base neurosurgeon, neuroradiologist, and neuroanesthesiologist. In patients at high risk for an ICA injury the discussion should include a neurointerventional radiologist or endovascular neurosurgeon. Preemptive decisions, such as the need to assess the brain collateral circulation or to sacrifice the ICA as part of the tumor resection, are discussed at this time. Other specialties, such as medical oncologists, radiation oncologists, neuro-ophthalmologists, and endocrinologists, are consulted based on the needs of each case. Furthermore, complex skull base lesions are best managed in comprehensive medical facilities with appropriate diagnostic and therapeutic capabilities.
Imaging is highly valuable not only as a diagnostic tool but also in planning the most appropriate surgical approach and providing detailed anatomy of the ICA course. Consequently, it allows the team to identify patients at risk, thus fostering the required precautions ( Fig. 1 ). It has been shown that preoperative imaging decreases the complication rate of endoscopic sinus surgery. Computed tomography (CT) and MRI, with and without contrast, provide complementary information and are customary in the primary evaluation of skull base lesions. Other imaging modalities, such as CT angiogram, MR angiogram, and/or digital subtraction angiogram provide a detailed evaluation of vascular structures and their relationship to the surgical corridor, tumor, and planned resection.
High-risk cases ought to be discussed thoroughly with the neurointerventional radiologist or endovascular neurosurgeon. A balloon test occlusion (BTO) of the ICA is required to assess the adequacy of the collateral cerebral blood flow, and therefore evaluate the potentially deleterious effect of losing one’s ICA (see Fig. 1 ). A BTO, even when performed under neurologic surveillance as the only parameter, considerably reduces the incidence of postoperative stroke compared with indiscriminate ICA sacrifice. The addition of objective measurements of cerebral blood flow by xenon CT, transcranial Doppler, scintigraphy, or other methods increases the sensitivity of the technique and categorizes the risk for an ischemic stroke. However, even the best BTO is associated with a 5% to 10% false-negative rate resulting in a delayed stroke after therapeutic ICA occlusion, and cannot predict embolic phenomena. Additionally, a BTO is associated with a 3% to 4% procedural risk related to intimal damage resulting in arterial dissection and/or pseudoaneurysm formation and consecutive thromboembolism. The benefits of an elective BTO should be weighed against the risks of the procedure and the rate of false-negative findings. Therefore, the procedure is reserved for those patients who carry a high risk of ICA injury (see Fig. 1 ).
Preoperative preparations should also include the optimization of medical comorbidities and cessation of drugs that may increase the tendency for bleeding. Preoperative counseling and informed consent are obligatory steps. Operative risks and expected complications and the possible need for further endovascular treatment should be thoroughly explained. Additionally, the patient should be informed regarding the possibility of using external approaches to manage unforeseen situations. Furthermore, all available treatment options and the goal of the surgery should be discussed in a multispecialty tumor board or planning conference setting. This is especially advocated for patients at high-risk for injury, for whom alternative therapies must be weighed against surgery.
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