The carotid body was first described by von Haller in 1743 . It is highly specialized organ located at the common carotid artery bifurcation. Its feeding vessels run primarily from the external carotid artery. The function of the carotid body is related to autonomic control of the respiratory and cardiovascular systems, as well as blood temperature [3, 10, 12, 15–23]. Paraganglioma is a relatively rare neoplasm occurring in carotid body [1–6].
The carotid body paraganglioma is more common in women [2–5, 20, 25–28]. The incidence of bilateral carotid body lesions is approximately 10%. Most of these lesions are benign however malignant behavior is often encountered. For diagnosis of malignant carotid body paraganlioma there are no clear histological characteristics that differentiate it from benign lesions. This diagnosis is reserved for the tumors with local, regional and distant metastasis. The rate of malignancy is reported to be 6–12.5% of all cases [3–5, 9, 11, 29–35]. The 7–9% of the cases are hereditary [2, 4, 20, 25–28, 36]. None of our cases were bilateral or hereditary.
Carotid body paraganglioma often present as slow growing, non-tender neck masses located just anterior to the sternocleidomastoid muscle at the level of the hyoid. The tumor is mobile in the lateral plane but its mobility is limited in the cephalocaudal direction [3–5, 13–15, 21, 26, 36–38]. Occasionally the tumor mass may transmit the carotid pulse or demonstrate a bruit or thrill . Because of its location in close approximation to carotid vessels and X-XII cranial nerves, tumors enlargement causes progressive symptoms such as dysphagia (two of our cases), odynophagia, hoarseness of voice (two of our cases) or other cranial nerve deficits [2–5, 14, 26, 27, 32, 37, 40]. The patients may give a history suggestive of symptoms associated with catecholamine production such as fluctuating hypertension, blushing, obstructive sleep apnea and palpitations [3–5, 10, 14, 15, 21–23, 37].
Size of the tumor has a great importance not only for its clinical manifestations but also for treatment. In 1971, Shamblin introduced a classification system based on tumors size . They classified small tumors that could be easily dissected away from the vessels as group I. Group II (7 of our cases) included paragangliomas of medium size that were intimately associated and compressed carotid vessels, but could be separated with careful subadventitial dissection. Group III consisted of (5 of our cases) tumors that were large and typically encased the carotid artery requiring partial or complete vessel resection and replacement. Histologically, carotid body paraganglioma resemble the normal architecture of the carotid body. The tumors are highly vascular, and between the many capillaries are clusters of cells called Zellballen .
The carotid angiography is the most useful diagnostic test for paragangliomas. The angiography demonstrates tumor blood supply and widening of the carotid bifurcation by a well-defined tumor blush ("lyre sign"), which is classic pathognomonic angiographic finding [5, 8, 37–39, 42, 43]. MR and contrast CT are more effective non-invasive imagining modalities comparing with duplex ultrasonography, especially for small tumors [3, 37–39, 42–45]. Radioimmunodetection of carotid body paraganglioma by 111In labeled anti-CEA antibody is also described in literature [9, 46]. The differential diagnosis includes other tumors in this area, carotid artery aneurysms and elongation. For this reason using of precutaneous fine-needle aspiration for preoperative diagnosis of carotid body paraganglioma, can be very dangerous .
Resection of carotid body paraganglioma carries inherent risks of injury to the cranial nerves, carotid arteries as well excessive blood loss. Reigner first attempted resection of a carotid body paraganglioma in 1880, but the patients did not survive . Maydel was the first to remove a carotid body paraganglioma successfully in 1886, but the patient became aphasic and hemiplegics due to internal carotid artery ligature . In 1903, Scudder performed the first successful removal of carotid body paraganglioma . The surgical excision with careful subadventitial dissection is treatment of choice for most carotid body paragangliomas (Shamblin I and II) [2–6, 14–18, 34, 37–40, 43]. The Shamblin III of carotid body paraganglioma requires resection of the external and/or internal carotid artery. If the internal carotid is encased in tumor or damaged during resection, immediate repair/replacement should be performed [15, 37, 39, 40, 42, 43, 51, 52]. The second problem during tumor excision is bleeding, which sometimes can be massive. In such cases clamping of all carotid arteries is useful, with placement of internal carotid shunt [18, 35, 37]. Having in mind our experience with surgical treatment of both carotid body gangliomas as well as carotid stenosis, we recommend Pruitt-Inahara double balloon occlusive internal carotid shunt . The placement of this shunt through incision on the common carotid artery contributes to the adequate bleeding control from the common and internal carotid arteries, as well as brain protection. This procedure gave a clean and dry operative field during tumor removal [3, 37]. Some other articles recommend angiographic embolization preoperatively [3, 23, 37, 42, 53–55]. The Preoperative embolization of a carotid body paraganglioma can be performed by ethanol or polyvinyl alcohol. The finally result is a complete devascularization . Earlier the carotid body paragangliomas were considered radioresistant . However, more recent studies indicate good responses to radiation therapy [11, 30]. Most authors recommend radiotherapy for giant and recurrent carotid body paragangliomas, and with malignant carotid body paragangliomas metastatic to the regional lymph nodes [8, 33–36].
The modern surgical techniques have reduced the risk of postoperative stroke in carotid body paraganglioma resection to less than 5% [37, 40, 56]. However, the incidence of cranial nerve injury remains strikingly high, ranging from 20% to 40% [37, 38, 48, 56, 57]. In 20% of patients the neurological deficits is permanent. We found two (18%) transient hypoglossal, and one transient vagus nerve damage. recurrence after complete resection occurs in approximately 6% of patients [15, 37, 39, 40, 42, 43, 51, 52]. In our study however, there were no recurrences. The patients with internal carotid artery reconstruction should undergo duplex scanning periodically to identify graft stenosis.