Carotid Body Tumors Treatment & Management

Radiotherapy as a primary modality of treatment for carotid body tumors (CBTs) has been heavily debated, because some investigators have found that these tumors are not radiosensitive and have reported regrowth after suppression. The tumors that are treated primarily with radiation are also difficult to resect afterwards because of radiation-induced fibrosis. Other investigators have reported no cure rates for patients who received radiation for their carotid body tumors (CBTs). The primary goal of radiotherapy is to slow or halt progression.

For these reasons, surgery is usually the treatment modality of choice for younger, healthier patients with carotid body tumors (CBTs), and radiotherapy is reserved for the elderly, patients who are poor surgical candidates, and selected individuals with multiple paragangliomas in whom resection may be highly morbid.

Patients with metastatic disease may be candidates for external beam radiation, chemotherapy, iodine-131 (¹³¹I)-MIBG therapy, or clinical trails. Consultations with the appropriate services, such as endocrinology, radiation oncology, and medical oncology, is necessary for these patients. ^[29]

Carotid body tumors (CBTs) are treated with either surgery or radiotherapy. When choosing treatment, consider the following factors: presence of other paragangliomas, bilateral carotid body tumors, the age and the health of the patient, and the patient's preference. ^[4]

In a study by Dorobisz et al of 49 carotid body paragangliomas (47 patients) managed with surgery, including 43 simple resections, treatment of 40 tumors (82%) was uneventful, with patients experiencing an uncomplicated postoperative period. ^[30]

Nonetheless, surgical treatment of carotid body tumors can be associated with significant morbidities, especially with large Shamblin III tumors (greater than 5 cm). ^[31] For this reason, patients who have poor medical conditions, elderly patients, or patients with recurrent tumors are usually treated with radiation therapy.

Preoperative evaluation is extremely important to avoid major surgical complications. The use of MRI and genetic testing in susceptible families have allowed earlier detection of multicentric tumors in many patients. Operative risk is directly related to the size and extent of the tumor.

Preoperative embolization is still controversial, although it has been used to decrease the risk of intraoperative bleeding, particularly in larger tumors. ^[32]  A study by Cobb et al indicated that presurgical tumor embolization provides no benefit in patients undergoing carotid body tumor (CBT) resection, finding no significant differences in mortality, cranial nerve injury, and blood loss between patients who underwent embolization and those who did not. Moreover, as evaluated following risk adjustment, embolization was associated with a greater length of stay. ^[33]

In contrast, a literature review by Texakalidis et al reported that in patients who underwent embolization prior to resection, intraoperative blood loss was significantly lower and operative time shorter than in those who did not. Moreover, the investigators found the length of stay to be similar between the two groups. ^[34]

Carotid body tumors are rarely associated with pheochromocytomalike symptoms, but checking urinary catecholamines, vanillylmandelic acid (VMA), and metanephrines is helpful and is routine in many centers.

Preoperative imaging is necessary to evaluate the extent of the disease and its multiplicity. If catacholamine levels are elevated, an evaluation for adrenal pheochromocytomas should be performed. If detected these tumors should be removed prior to the carotid surgery.

Carotid balloon test occlusion is performed in patients who are at a high risk of carotid resection due to the tumor’s involvement. In such cases, consultation with a vascular surgeon and a neurologist for intraoperative EEG monitoring may be necessary.

In addition to the above testing, discussion with the patient about the postoperative complications is extremely important; this includes the risks of cranial nerve injuries (IX, X, XI, XII), bleeding, infection, the possibility of a carotid bypass or vein grafts, stroke, and death. ^[35]

Embolization of carotid body tumors has been a controversial topic. It has been recommended by some surgeons when the size of the tumor exceeds 4 cm in size. Blood loss appears to be less with prior embolization of larger tumors. Bilateral arteriography can also be performed to delineate the vascularity of the tumor and to detect any tumors on the contralateral side.

A study by Zhang et al indicated that preoperative tumor embolization, carried out less than 48 hours before surgery, can significantly reduce blood loss, surgical time, and length of hospital stay in patients undergoing carotid body tumor resection. The investigators warned that embolization should be carried out only in vessels that can be subselectively catheterized and that do not permit contrast medium to freely reflux into the internal carotid artery. The study involved 32 patients, including 21 patients who underwent embolization and 11 who did not. ^[36]

In contrast, a literature review by Abu-Ghanem et al indicated that in carotid body tumor resection, preoperative embolization is no more effective than nonembolization in terms of estimated blood loss, length of surgery or of hospital stay, or risk of stroke, cranial nerve injury, or vascular injury. ^[37]

A study by Cobb et al also indicated that preoperative arterial embolization does not contribute to the safety of carotid body tumor resection. The investigators found that rates of mortality, cranial nerve injury, and blood loss did not significantly differ between patients in the study who underwent carotid body tumor resection alone and those who first underwent preoperative embolization. ^[38]

Effective communication between the surgeon and the anesthesiologist is of utmost importance throughout the surgery. Whether the patient is totally relaxed is the surgeon's preference. Some surgeons prefer paralysis to aid in muscle retraction and to facilitate the use of electrocautery. Others prefer the patient not be paralyzed, which, they feel, aids in the identification of the cranial nerves.

Different types of neck incisions have been described. The incision chosen is usually based on tumor size and extent. A horizontal incision in the mid neck affords excellent exposure both superiorly and inferiorly and typically provides excellent cosmesis. Some surgeons prefer an endarterectomy approach using a transverse cervical incision along the anterior border of the sternocleidomastoid. For larger tumors, many incisions have been described, including preauricular extension of the incision for tumors extending to the infratemporal fossa.

The most important step in tumor removal is superior and inferior control of the blood vessels. This includes identification of the internal jugular vein, common, and internal carotid arteries and placing vessel loops on each. (In a report on 11 patients with Shamblin II or III carotid body tumors, Spinelli et al described a surgical technique in which resection of the tumors from the internal carotid artery was performed bloodlessly by clamping the external carotid artery [at its origin and distal branches] but not the internal carotid artery. ^[39] )

In cases in which the tumor is not involving the hypoglossal and vagus nerve, these nerves should be exposed and followed cranially. Identification of the accessory and glossopharyngeal nerve is also performed; in certain cases, the digastric muscle must be sacrificed for better exposure.

The small feeder vessels, together with some branches from the external carotid artery, are ligated. Dissection between the external and internal carotid artery exposes the larger feeding vessels, including the ascending pharyngeal artery, which is the main feeding vessel most of the time. This is followed by a craniocaudal dissection of the tumor from the carotid vessels. In tumors that are identified intraoperatively as Shamblin type III, the plane of dissection can be found on either the dorsolateral side of the internal carotid or the ventrolateral side of the external carotid.

Dissection of the carotid body tumor is performed in the subadventitial plane using either loupes or microscope, as described by Gordon-Taylor. This is supplemented with the use of bipolar cautery, which limits blood loss and controls bleeding.

Any injury to the carotid vessel requiring clamping of the common or internal arteries needs temporary heparinization with a low risk of complications; this is often followed by vascular reconstruction. van der Mey reported that 65% of patients who had their internal carotid artery ligated had a stroke and that 25% of patients who passed their balloon occlusion test had a delayed stroke. ^[40]

During removal of the carotid body tumor, care should be taken once again to avoid injuring the nerves, especially the superior laryngeal nerve, which has been reported to be the most injured nerve during dissection. This nerve is frequently involved with tumor posteriorly. Ideally, it can be identified and dissected as it exits the vagus nerve and courses medially towards the larynx.

In the immediate postoperative period, the patient should be carefully observed for any complication of the procedure, including postoperative hemorrhage or late stroke. In patients who underwent vascular reconstruction, ICU admission is recommended, along with heparinization.

Patients should be closely observed for any local recurrence, although these are usually rare. If the patient has no morbidity from the initial surgery, contralateral tumors should also be resected. In patients with significant permanent morbidities to cranial nerves, radiation to the contralateral side might be considered. As always, a careful weighing of pros and cons must be done and presented to the patient. Operating on small tumors has a very low rate of complications and the long-term effects of radiation on younger patients is potentially a contraindication.

Careful subadventitial dissection of the tumor and control of the proximal and distal carotids minimizes vascular complications. Of note is that the size of the tumor and involvement of the carotid artery predict the vascular complication risks. The highest risk is observed in tumors larger than 5 cm and/or grade 3 by Shamblin classification. These patients with large tumors also have more frequent postoperative cranial nerve injuries. ^[28]

A study by Kim et al indicated that in carotid body tumor resection, for every 1 cm reduction in tumor distance to the skull base, the risk of a greater than 250 mL blood loss increases 1.8 times, and the risk of cranial nerve injury increases 1.5 times. ^[41]

The most commonly injured nerve is the superior laryngeal nerve. This nerve supplies the cricothyroid muscle and provides sensation to the supraglottic larynx. The patient postoperatively might suffer from some degree of aspiration and voice changes (inability to create high-pitched sounds).

Injury to the vagus nerve results in vocal cord paralysis with resultant hoarseness and increased aspiration risk. When combined with a superior nerve paralysis, as is the case with a high vagal injury, aspiration is a significant problem because the larynx not only does not function well but is also anesthetic. This may be compensated by the contralateral vocal cord over time. If the problem persisted, then vocal cord medialization procedures should be performed.

Speech and swallowing problems result from a hypoglossal nerve injury. If the nerve is accidentally cut, primary reanastomosis should be attempted first. If primary anastomosis fails, then other options include a greater auricular nerve graft.

Postoperative shoulder pain and weakness is typically a result of an accessory nerve injury. This results in significant disability for the patient.

First bite syndrome is another complication that occurs when the sympathetic supply to the ipsilateral parotid gland is severed. The resultant parotid gland has an unabated parasympathetic supply. To date, no successful treatment of this syndrome exists.

In cases of bilateral tumor excision with loss of the bilateral Hering nerves, patients experience labile blood pressure postoperatively, which is difficult to control medically. Concurrent excision of bilateral carotid body tumors should, therefore, be avoided, although staging the surgeries might help because of the compensation provided by the aortic receptors.