The introduction of preoperative reinforcement of the ICA with stents is a significant advancement in the surgical management of patients who are at risk of damage to the ICA. Stent insertion reinforces the artery and allows more aggressive carotid dissection while reducing the possibility of intraoperative injury to the ICA. To reduce the risk of thromboembolic complications, antiplatelet therapy is commenced 5 days before the stent insertion using a combination of clopidogrel (75 mg/day) and aspirin (100 mg/day). This therapeutic regimen is administrated for 1–3 months after stenting and then reduced to single-drug treatment with aspirin only. Antiplatelet agents are stopped and low molecular weight heparin (LMWH) commenced 5 days before surgery. Antiplatelet agents are introduced 2 days after surgery and LMWH is stopped 3 days after surgery. The patient then is placed on lifelong antiplatelet therapy (Fig. 9.6).

Reinforcement with stents is performed under general anesthesia as a separate procedure following diagnostic angiography. Three different types of self-expanding nitinol stents are used: Xpert Stent System (Abbott Laboratories Vascular Enterprises, Dublin, Ireland), Neuroform 3 (Boston Scientific, Fremont, CA), and LEO (Balt Extrusion, Montmorency, France). We consider the Xpert stent the most suitable for reinforcement of both the cervical and intratemporal portions of the ICA because of its diameter (4 or 5 mm) and length (20, 30, or 40 mm). To reduce the possibility of injuring the ICA at the stent-tumor border, at least 10 mm of tumor-free vessel wall must be reinforced with the stent, both proximally and distally. To achieve this, it is necessary to insert up to two or even three stents. Each stent is carefully selected and tailored to the individual patient. It is difficult to negotiate the stent between the vertical and horizontal portions of the carotid canal and in arteries that are coiled or kinked in the neck, and great care must be taken while this is being performed. In such situations, softer and more flexible stents must be chosen, to reduce the risk of dissection of the ICA. If a stent placement is technically impossible, a PBO is the next option.

The timing of reinforcement with stents also plays an important role; an interval of at least 4–6 weeks is advocated between stenting and surgery. This allows the formation of a stabilized neointimal lining (Fig. 9.7) on the luminal surface of the stent. In the presence of significant blood supply from the ICA, a bare stent is ineffective in reducing the vascular supply to the tumor. In such situations, the use of PBO, preoperative embolization with particles during temporary balloon occlusion of the ICA, and insertion of covered stents are possible alternative solutions. Present literature suggests that covered stents have several theoretical disadvantages, increased thrombogenicity, rigidity, and greater difficulty in positioning at arterial angles, when compared to bare stents.

One month after the stent insertion, the neointimal layer is developed and subsequent subadventitial dissection can be safely performed.

Intraoperatively, the ICA may require the following types of intervention, depending on degree of involvement: (1) decompression with or without partial mobilization of the artery, (2) subperiosteal dissection, (3) subadventitial dissection, (4) subadventitial dissection with stent coverage, and (5) arterial resection (after preoperative PBO).

Simple decompression—This technique is employed when the tumor is around the ICA but not adherent to the artery (i.e., Fisch class C1 TJPs). Decompression of the ICA is performed after identifying it medial to the Eustachian tube by drilling out the tympanic bone. A large diamond burr is used parallel to the course of the artery. Drilling is advanced both laterally and medially to the artery. By removing the bone anterior to the ICA, the artery can be displaced laterally or medially by manipulating it with the tip of the suction tube while drilling is being performed. If additional drilling around the ICA is required, a vessel loop is wrapped around the artery to enable a wider range and better control.

Subperiosteal dissection—This technique is indicated when the tumor involves the periosteum of the carotid canal without reaching the adventitia. In this technique, a plane of dissection is developed between the adventitia of the ICA and the periosteum of the carotid canal [20]. This is relatively easier and safer in the vertical petrous segment, as the ICA is thicker and more accessible when compared to the horizontal segment. The dissection of the tumor is started at the cervical level, from an uninvolved extratemporal segment of the ICA, where a good plane of dissection is easily identified. The bone of the carotid canal around the ICA from its entrance into the temporal bone is drilled out along with the tumor infiltrating the bone and periosteum. Gentle displacement of the ICA, from its entrance in the skull base to at least the genu of the horizontal segment, is required if the tumor has extended anterior to the artery. There could be areas where the tumor may extend into the adventitia of the artery, and subadventitial dissection may be required.

Subadventitial dissection—This technique is applied to tumors that infiltrate the adventitia without reaching the muscular layer (media) of the ICA. Subadventitial dissection consists of separating the adventitia from the muscular layer. The wall of the ICA at the level of the vertical segment is 1.5–2.0 mm thick with the adventitia being approximately 1 mm thick. The adventitia is absent at the horizontal portion [21]. Therefore, subadventitial dissection can only be executed at the vertical portion. The intraoperative risk of a vascular injury is especially high in irradiated or previously operated cases. Small lacerations to the arterial wall, or any avulsion of the caroticotympanic branches, can often be controlled with judicious use of the bipolar cautery. For small to medium defects, direct suture repair is recommended. Double-armed vascular sutures are used while temporary occlusion is applied. Care to evert the edges of the artery while suturing is important to avoid stenosis. The postoperative risks of subadventitial dissection include weakening of the vessel leading to subsequent blowout or to dilatation and delayed aneurysm formation.

Following balloon occlusion of the artery, dissection is started from cervically upward. It is ligated immediately proximal to the proximal balloon using a large vascular clip, followed by en bloc resection of the artery with the surrounding tumor. Care must be taken to identify the distal segment of the occluded artery and perform transection here, to avoid excess traction on the cavernous sinus segment during final tumor removal (Fig. 9.8).

In rare cases with failed tumor embolization due to high flow of tumor blood supply, permanent balloon occlusion can be performed even in cases with stent insertion (Fig. 9.9).

Prevention of injury to the ICA must be achieved at all costs. However, on rare occasions, a vascular injury may be encountered [22, 23]. In such case, the presence of proximal and distal control allows temporary occlusion, while a primary repair is carried out. A primary principle in such a situation is to achieve adequate visualization. Temporary compression or occlusion is achieved quickly by using previously placed control tapes. A variety of atraumatic vascular clips can also be used. Back-bleeding is a reassuring sign indicating some degree of collateral flow and allowing repair to be carried out in a timely fashion. Once the controls are achieved proximally and distally, small lacerations to the arterial wall or avulsion of the caroticotympanic branches can often be controlled with judicious use of the bipolar. Fine tips are used to approximate the edges in the longitudinal direction of the laceration. A low energy pulse is applied, and the forceps are advanced, and the process is repeated until the laceration is sealed. The occlusion is partially and then fully released to ensure closure. A layer of Surgicel^® is placed over the repair and reinforced with fibrin glue. For small to medium defects, direct suture repair is recommended. Double armed vascular sutures are used while temporary occlusion is applied. Care to evert the edges is important as to avoid significant stenosis. Patch grafting and bypass using saphenous vein are options in extreme situations. In case of a stented ICA, the greatest risk is potential injury is at the transition point of the stented and non-stented artery. It is imperative to use minimal traction at this point. Facilities for rapid transfer of the patient to the neuroradiology suite once temporary control is gained are essential, with the options of emergency balloon occlusion or covered stent placement [24]. Apart from repair of the artery, important resuscitation principles must also be adhered to. Judicious volume replacement, estimation of blood loss, and consideration of component therapy were made. Following repair, normotension and adequate circulating volume must be maintained to ensure adequate repair and maintain neuroprotection. Any injury to the internal carotid artery or subadventitial dissection must be followed up radiographically due to the risk of pseudo-aneurysm formation.