Carotid Body Tumors

Abstract

Carotid body tumors (CBTs) are derived from parasympathetic autonomic nervous system cells and are the most common type of head and neck paragangliomas, accounting for 65-80% of lesions. CBTs may occur sporadically, may be familial with identified gene mutations on the succinate dehydrogenase subunit, or a component of familial neuroendocrine syndromes. Environments or medical conditions leading to chronic hypoxia can increase the risk of CBTs. The differential diagnosis of CBT include other neck masses such as enlarged lymph nodes or other neck tumors. Computed tomography or magnetic resonance angiography is often diagnostic as CBTs cause a characteristic splaying of the carotid bifurcation. The degree of encasement of the carotid arteries is classified by Shamblin Type I-III, and the higher Shamblin category correlates to highest risk of nerve injury after surgical resection. All tumors should be removed in healthy patients, with observation or radiotherapy reserved for high-risk or elderly asymptomatic patients. Tumor embolization may be considered in CBTs larger than 4cm. Resection, with or without tumor embolization, requires adequate exposure of the distal carotid with consideration of nasotracheal intubation or mandibular subluxation. The surgeon must be prepared to resect and replace the carotid artery in large CBTs using techniques similar to carotid endarterectomy to reduce stroke risk. Cranial nerves should be carefully exposed and preserved during a systematic dissection. Despite careful resection, cranial nerve injury may be as high as 30-40%, although only 5% are permanent. Stroke risk (1%) and mortality (<1%) are low. KEY WORDS: Carotid body tumor, succinate dehydrogenase, Shamblin Type, neuroendocrine tumors, parasympathetic autonomic nerve cells, tumor embolization