Surgery for Glomus Tumors and Carotid Paragangliomas

Jose N. Fayad

• Treatment options for glomus tumors and carotid paragangliomas include observation, radiation therapy, and microsurgical removal. The appropriate treatment is determined by tumor size, age of patient, presenting symptoms, and possible morbidity associated with treatment. Asymptomatic carotid body tumors in the elderly with significant comorbidities may best be observed.
  
• The treatment of choice for younger patients is surgical removal. Complete surgical removal is possible in 80% of patients. Long-term facial nerve function after surgery is good (House-Brackmann grade I or II) in 95% of patients. Approximately 20% of patients will require vocal cord augmentation or a gastric feeding tube due to aspiration. Occasionally, a patient will require a tracheostomy.
  
• Bilateral glomus vagale tumors pose a challenge and a risk of loss of both vagus nerves, possibly resulting in a fatal outcome. For this reason, when one of these lesions is very large and symptomatic, and the contralateral vocal cord is functional, the larger tumor can be treated surgically and radiation therapy considered for the second lesion. In other bilateral cases, treatment with radiation may be recommended for both tumors.

• Clinically significant secretion of catecholamines is identifiable in only 1 to 3% of tumors and unlikely in glomus tympanicum tumors. In secretory tumors, a search should be made for concomitant pheochromocytomas, especially if high levels of epinephrine are detected. In patients with clinical symptoms, preoperative measurement of serum catecholamine levels and 24-hour urinary metanephrines and vanillylmandelic acid (VMA) testing is performed. Management of patients with secreting tumors includes perioperative blood pressure management with blocking agents, including phentolamine and phenoxybenzamine, and intraoperative invasive hemodynamic monitoring.

• Embolization is typically performed 24 to 48 hours prior to surgery for large tumors involving the jugular foramen and skull base. When the potential for sacrifice of major vessels exists, it is necessary to assess the cross-perfusion from the contralateral vessels. This is done using compression angiography, measurement of stump pressures, and temporary balloon occlusion. These studies are not 100% reliable, and more precise assessment is done using cerebral perfusion scans with single photon emission computer tomography (SPECT) imaging or xenon CT scan. Typically, patients who require sacrifice of an involved internal carotid artery and who perform well on these studies can be managed by preoperative permanent balloon occlusion. Those who fail the preoperative perfusion studies may require revascularization at the time of the resection.

• General anesthesia is preferred in all cases.
  
• With the exception of small glomus tympanicum tumors, an arterial line and central venous pressure line are inserted. Six units of blood are typed and crossmatched at the beginning of the procedure because of the risk of significant blood loss from these tumors.
  
• During the actual tumor dissection, particularly around the major vessels, the mean blood pressure is maintained at ~80 mm/Hg in younger patients and higher in older patients. The blood pressure is regulated pharmacologically with a continuous nitroglycerin infusion. This allows for rapid reversal of hypotension, if needed.
  
• Intraoperative facial nerve monitoring is routinely performed.

• Complete tumor removal is possible through a transcanal approach. It is important to extend the tympanomeatal flap more inferiorly and anteriorly than in the usual fashion for stapes surgery so that the inferior aspect of the tympanic membrane can be fully elevated and the hypotympanum can be visualized and accessed.
  
• The artery that usually supplies these tumors is the tympanic branch of the ascending pharyngeal artery, and bipolar electrocautery is usually effective in securing hemostasis. Avoid unipolar electrocautery to prevent injury to the cochlea and the possibility of sensorineural hearing loss. Surgicel will be needed to occlude the bony canaliculus from which the vessel arises.
  
• If there is bleeding from the superior extent of the tumor, it is important to be careful not to disrupt the ossicular chain or traumatize the facial nerve while obtaining hemostasis using Surgicel®. In tumors that extend posteriorly and superiorly involving the ossicular chain, it is essential to identify the ossicular chain and separate the incudostapedial joint to avoid trauma to the inner ear. Once the tumor is removed, the ossicular chain can be reapproximated.