20 Paraganglioma Embolization
Abstract
Head-and-neck paragangliomas are a relatively rare disease entity, but one that is encountered occasionally in clinical practice, particularly in tertiary care centers. Due to their highly vascular nature, location, and natural history, these tumors are most aptly treated with a multidisciplinary approach involving neurointerventionalists, head-and-neck surgeons, vascular neurosurgeons, and vascular surgeons. The decision to proceed with preoperative embolization of these tumors is controversial, with many conflicting studies supporting surgical resection with or without preoperative embolization. Due to their relatively rare incidence, it has been difficult to study the role of preoperative embolization with rigor, but a close analysis of the available literature is important for the appropriate neurointer-ventional management of these tumors.
Keywords: carotid body tumor, paraganglioma, embolization
20.1 Goals
1. Review and understand the literature that describes the symptomatology and natural history of head-and-neck paragangliomas, specifically carotid body tumors (CBTs).
2. Review the classification scheme of CBTs and how it applies to the treatment decision for these tumors.
3. Critically analyze the literature that evaluates the utility of preoperative embolization of these tumors.
20.2 Case Example
20.2.1 History of Present Illness
A 47-year-old female presents for a painless and progressively enlarging swelling of the right side of her neck. An ultrasound ordered by her general internist revealed an approximately 5-cm mass situated at the right carotid bifurcation. The patient initially noticed this swelling 16 months ago, but it has noticeably enlarged since that time, albeit slowly. She also complains of hoarseness of her voice that started approximately 1 year ago. She denies any difficulty swallowing, or other significant neurologic complaints.
Past medical history: Chronic headaches, basal cell carcinoma, asthma.
Past surgical history: Excision of a basal cell carcinoma of the right face, open reduction and internal fixation of a left humerus fracture.
Family history: Denies any familial history of cancer or masses.
Social history: Two to three glasses of red wine per week, no smoking or other illicit substance use. Review of systems: As per the above.
Examination: There is a firm, nontender, and pulsatile mass of the right neck at the anterior border of the right sternocleidomastoid, mobile in the medial-lateral direction but immobile in the rostral-caudal dimension (Fontaine sign). Firm compression of the mass leads to a slight decrease in its size, with re-expansion on release of pressure in a series of pulsations (sign of Recluse and Chevassu).1 Her voice is slightly hoarse, but otherwise her physical and neurologic examination is unremarkable.
Imaging studies: See figures.
Carotid Doppler: A 5-cm heterogeneously hypoechoic circumscribed mass in the right neck, lateral to the right submandibular gland, with the medial aspect of the mass inseparable from the adjacent carotid vasculature and carotid bifurcation, which remains widely patent.
Computed tomography (CT) neck with contrast in ▶ Fig. 20.1 shows an avidly enhancing mass in the right carotid space that splays the proximal right internal and external carotid arteries. It is intimately associated with the carotid bulb, measuring 5.0×4.2×4.0 cm, most consistent with a carotid body tumor. The tumor partially encases both the right external and internal carotid arteries, consistent with a Shamblin 2 carotid body tumor.
Diagnostic cerebral angiogram in ▶ Fig. 20.2a, b demonstrates a hypervascular lesion at the right carotid bifurcation that splays the internal and external carotid arteries apart. The tumor receives vascular supply primarily from robust branches from the ascending pharyngeal artery, the superior thyroid artery, and occipital artery. There is no significant tumor blush identified from selective injections of the right internal carotid artery. There was no vessel wall abnormality to suggest significant invasion of the internal or external carotid arteries. The patient had a widely patent anterior communicating artery with brisk collat-eralization from left common carotid artery injections.
▶ Fig. 20.2c, d: Diagnostic cerebral angiogram postselective catheterization and embolization. The ascending pharyngeal, superior thyroid, and occipital arteries were selectively cathe-terized and embolized with a combination of polyvinyl alcohol (PVA) particles and Onyx, with overall a 95% reduction in tumor blush.
20.2.2 Treatment Plan
The patient agreed to definitive treatment of her right-sided CBT, which included preoperative embolization followed by surgical resection with an interdisciplinary team including an experienced neurointerventionalist, vascular neurosurgeon, and otorhinolaryngologist.
20.2.3 Follow-up
The patient did very well after definitive treatment of her right CBT, including preoperative embolization followed by surgical resection by an interdisciplinary team involving a neurointerventionalist, vascular neurosurgeon, and otorhinolaryngologist. Total operative time for surgical resection was 189 minutes with an estimated blood loss of 100 raL The patient was discharged home on postoperative day 2, with 1 additional day of hospital stay preceding surgical resection for her embolization. The patient remained at her neurologic baseline following surgery, with slight hoarseness. At her 6-month follow-up appointment, she had persistent mild hoarseness of voice, but otherwise had no complaints.
Fig. 20.2 Angiogram of right-sided carotid body tumor in the (a) anteroposterior, and (b) lateral projections prior to embolization. Postembolization angiogram of the same carotid body tumor in the (c) anteroposterior and (d) lateral projections.
20.3 Case Summary
1. What are the general characteristics, symptomatology, and natural history of carotid body paragangliomas? Paragangliomas are highly vascular, slow growing, and relatively rare tumors of neural crest cell origin with an incidence of approximately 1:30,000.23 CBTs are the most common paraganglioma of the head and neck and account for roughly 70% of head-and-neck paragangliomas.3 They originate from the carotid body, as their namesake implies, and they are generally nonsecretory, although 10% can be.4 Historically they have been called by many names including chemodectoma, glomus caroticum, in addition to carotid body paraganglioma. They derive their blood supply from branches of the external carotid artery, with the most common arterial supply coming from branches of the ascending pharyngeal artery.5
A majority of CBTs are diagnosed due to an insidious neck swelling, typically at the anterior border of the sternocleidomastoid muscle.6 The mass tends to be firm and painless and can be pulsatile due to their high degree of vascularity. These tumors are usually highly mobile in the medial-lateral direction but resist manipulation in the rostral-caudal dimension due to the tumor’s attachment to the carotid body and carotid bifurcation (Fontaine’s sign).1 CBTs also may be found due to progressive cranial nerve dysfunction, including hoarse voice or difficulty swallowing.7,8 A minority of these masses are found incidentally.
These lesions are typically slow growing and their symptomatology is explained by direct compression of nearby neurovascular structures, with an average rate of growth of 0.5 cm per year.9 While mostly benign, there is a small but definite risk of malignancy that is approximately 2 to 5%.10,11,12 The treatment modality of choice for these lesions is surgical resection with or without preoperative embolization, given their predictable growth and small, but definite, risk of malignancy.
2. What patient factors would you consider when deciding on your re commendation for treatment versus observation?
As with all candidates for surgery, the age and medical comorbidities of the patient need to be carefully considered in the context of the patient’s symptoms. A young, relatively healthy patient should have definitive treatment of their paraganglioma regardless of symptomatology as the natural history dictates that the tumor will invariably enlarge and eventually become symptomatic.7,8,9,10,11,12 However, an elderly patient with multiple medical comorbidities and an asymptomatic or mildly symptomatic CBT may be better served by either close observation or radiation therapy, as opposed to undergoing a relatively higher risk surgery.
3. What tumor factors would you consider when deciding on your recommendations for observation or treatment of carotid body paragangliomas?
Classification of carotid body paragangliomas based on operative risk was first proposed by Shamblin in 1970 based on retrospective review of 90 patients who underwent CBT resection.5 He identified three groups in his classification scheme, with group 1 including CBTs that were not associated with the carotid vessels and were easily dissected from the vessel adventitia. Group 2 includes those tumors that partially encase the carotid vessels, while group 3 includes tumors that completely encase the carotid artery. Group 1 tumors are the easiest to surgically resect, while the group 3 tumors are much more difficult, sometimes requiring external carotid artery sacrifice or internal carotid artery repair.
The Shamblin grade alone does not inform a decision regarding the need for surgical resection as these lesions should be surgically resected if the patient is medically able to tolerate surgery. It does, however, inform the surgeon of the potential difficulty of surgical resection and potential benefit of adjuvant treatments, such as preoperative embolization. Group 2 and 3 patients’ tumors are more difficult to dissect and resect due to their proximity to and involvement of the carotid vasculature, making vessel injury requiring repair or bypass more likely. This potentially could increase intraoperative blood loss, operative time, and potential for ischemic events or strokes.13,14,15
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