الفهرس 
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Abstract
SUMMARY UMMARY
arotid body originates from the third branchial arch mesoderm and from ectodermal-derived neural crest lineage the normal carotid body is an ovoid pink structure approximately 6 x 4 x 2 mm in size. It is commonly described, perhaps erroneously, as located posteriorly within the adventitia at the bifurcation of common the carotid artery.
The gland is innervated by the glossopharyngeal nerve. Its blood supply is the richest per gram of tissue of any tumor and is derived from vasa vasorum, branches of the vertebral artery, and, predominately, from the external carotid artery via its branches.
Characteristic feature of carotid body tumors is slow growth rate, which is reflected clinically by the delay between the first symptoms and the diagnosis, which averages between 4 and 7 years of age.
Carotid body tumor usually presents as a lateral cervical mass, which is often less mobile in the craniocaudal direction because of its adherence to the carotid arteries. The mass of the carotid body tumor is located lateral to the hyoid, whereas the vagal body tumors are found more cranially behind the ascending part of the mandible and sometimes project into the lateral oropharynx as a pulsating mass with displacement of the tonsil, soft palate, and uvula. Many carotid body tumors are pulsatile by transmission from the carotid vessels or less commonly expand themselves, reflecting their extreme intrinsic vascularity. Sometimes, a bruit may be heard by auscultation, but can disappear with carotid compression.
Angiography of the carotid system was the final diagnostic method for these lesions. Today, the diagnosis can be made with MR imaging in axial and coronal planes. The settings should include gadolinium-enhanced three-dimensional time-of-flight sequences, which demonstrate the extension of the tumor in relation to the carotid arteries and the involvement of the base of the skull. Additionally, MR imaging provides a perfect screening tool for multifocal (i.e., occult) head and neck paragangliomas.
Magnetic resonance imaging and MR angiography provide good insight into the vascularization of the tumor and the origin and contribution of the several branches of the external carotid Differential diagnosis, including other vascular or nonvascular tumors in the neck, can also be made. These include branchial cleft cysts, metastatic carcinomas, lymphomas, schwannomas, salivary gland tumors, and carotid artery aneurysms.
Angiography, though no longer the first-line imaging method, remains valuable for preoperative evaluation, and the possibility of preoperative embolization. Angiography can confirm the
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diagnosis and can provide information about the vascular supply of the paraganglioma, the status of the carotid arteries (e.g., stenosis, irregularity), and the patency of the circle of Willis.
Shamblin classification has been widely used by physicians as a predictor of vascular morbidity and for surgical decision-making. A directly proportional relationship of the Shamblin group with blood loss and surgical time has also been reported.
Surgery of carotid body tumors should not be undertaken without careful preparation and the patient’s consent. A preoperative endocrinological analysis for bioactivity should be performed.
The rationale for surgical excision of carotid body tumors is based much on the local (i.e., personal) experience with this rare, highly vascular tumor. Some physicians favor aggressive surgical excision, given the risk for cranial nerve impairment caused by progressive tumor growth and the risk for malignant degeneration.
Alternatively, radiotherapy has been advocated with good results in local tumor control, although the definition of successful treatment is difficult in such an indolent neoplasm. Other investigators claim the tumor is not radiosensitive because there is no direct cell-killing effect, and report regrowth of initially regressed carotid body tumor. Moreover, radiation therapy rapidly leads to substantial sclerosis and fibrosis that complicate future surgery and in the long run may carry the risk of an induced malignancy.
The primary purpose of tumor embolization is to allow a successful complete resection of such a vascular tumor, as the control of bleeding can be quite challenging.
Our meta-analysis for evaluation of the effects of preoperative embolization on the outcomes of carotid body tumor surgery, included (14) studies with a total number of patients (n=477). The results of these studies showed no statistically significant difference between preoperative embolization group and non embolization group in carotid body surgery for (blood loss & operation time). Preoperative embolization did not reduce risk of postoperative complications