Complete resection of benign and malignant tumors of the head and neck is the most reliable method to achieve a cure. Curability of skull base tumors remains elusive due to difficulties in achieving complete tumor excision. The team approach using the skills of a neurosurgeon, otolaryngologist, and neuroradiologist is revolutionizing the concept of resectability, and therefore, curability.1
Nevertheless, controversy still exists about the advisability of resecting a CA invaded by tumor. The prognosis of patients with such lesions is generally poor. In addition, resection of the CA is associated with morbidity and mortality. Unselected carotid ligation causes significant cerebral ischemia in a large number of patients with associated mortality rates as high as 58%.7,10
Thus, some surgeons think that involvement of the CA prohibits surgical resection.11
On the other hand, some others advocate the resection of the CA when involved with tumor to improve cure rates.12,13
Methods of assessing the adequacy of cerebral circulation, modern anesthesia reducing the risk of intraoperative hypotension, and improved techniques of vascular reconstruction have made it possible to resect the CA.
There exist several methods to predict the safety of CA resection. Measurement of the back pressure in the distal CA stump has been used.14,15
Balloon test occlusion (BTO) has also been described.16
However, 5 to 20% of patients who are asymptomatic during BTO develop cerebral infarction following permanent CA occlusion.17
Other promising methods are xenon computed tomography cerebral blood flow imaging, technetium 99m hexamethylpropylenamine oxine single-proton emission computed tomography imaging, positron emission tomographic scanning, induced hypotension at the time of BTO, and intraoperative EEG.5
However, no test or combination of tests has been able to exclude definitively the possibility of cerebral ischemia after CA resection.18
“Stripping” the tumor off the CA has been proposed to avoid these ischemic complications,11,19
but this represents a subtotal resection. In 42% of cases, microscopic invasion of the adventitia and elastic media has been demonstrated.14
In addition, the question also exists as to whether radiation affects vasospasm and stripping of the adventitia might increase the susceptibility of the CA to malignant invasion and rupture.12,17
CA resection and vascular reconstruction using autogenous or synthetic material has been recommended to minimize the risk of ischemic complications.17,20
In a meta-analysis of 22 studies on vascular resection techniques by Snyderman and D'Amico,10
permanent neurologic sequelae were recorded in 17%. It was concluded that vascular reconstruction was not shown to significantly alter the risk of neurologic events following CA resection. Graft infection and anastomotic disruption with serious hemorrhage are the other risks associated with this technique.14,18
In addition, the idea that vascular reconstruction is not necessary in all patients has fueled the argument about the indication of this technique.1
The new technique studied in this experimental model has been named as extarterectomy by Nussbaum and colleagues,18
since the procedure entails removal of the complete external arterial wall. The technique was first described in a swine model by Lopes and Wakhloo.8,9
The concept relies on the endothelization that takes place rapidly after placement of the stent within the CA. This neointima can support the blood flow through the artery inside the stent, despite complete removal of the CA wall.18
Thus, cerebral blood flow is maintained without interruption during the entire procedure. This, in turn, minimizes the risk of ischemic complications.
Endothelization of the inner surface after intra-arterial stent implantation is a well-known and fully understood phenomenon.21
There are many animal studies and some applications on humans derived mainly from histopathologic examination of the resected coronary arteries that were stented previously. While the stent struts are engulfed by the intima in conjunction with neointima formation, endothelialization continues on the inner aspect of the vessel and is completed within 1 to 2 months. Histopathologic findings after human CA stenting, however, have recently been reported in an autopsy case.22
The authors demonstrated that after 8 months, the stented portion of the internal CA shows neointima formation ranging in thickness from 300 to 500 μm over the stent struts. This case gives further support to our hypothesis that endothelization and neointima formation after stent implantation in CA forms a stable and permanent inner layer and can bear arterial blood pressure even with the elimination of the vessel wall exterior to the stent struts.
The study of Lopes and Wakhloo8,9
and the first clinical application by Nussbaum and associates18
have demonstrated that neurologic sequelae were not experienced in any of the cases as in our experimental study. Complications reported in these previous studies were pseudoaneurysm in one animal8,9
and hemorrhage between the interstices of the stent.18
The latter was controlled with external pressure. Neither of these complications nor any other has been experienced in the present experimental study.