Carotid body tumors are 75% sporadic and 25% familial. Sporadic CBTs are usually unilateral. Bilateral CBTs suggest familial paragangliomas. In this case, biochemical testing with urine metanephrines and catecholamines should be done to rule out pheochromocytoma. Succinyl dehydrogenase mutations are another screening test for the index patient and family members with bilateral/familial CBTs. This enzyme is part of the citric acid cycle and is associated with other neuroendocrine tumors.
- More common in females
- Ages 50-70
- Have low chance of malignancy (5% of cases), unless the onset is young and/or with family history
- Almost never have endocrine fucntion
Shamblin Classifications
Shamblin classifications of CBT are based on how encroached the tumor is to the carotid bifurcation.
- Type I – there is no tumor encasement of the vessels, tumor size < 5 cm, and the carotid bifurcation isn’t widened. The tumor can be easily resected out.
- Type II – the tumor is attached to the arteries, but not circumferentially encased. This is more surgically demanding
- Type III – There is complete encasement of the ICA and ECA. Tumor size is > 5 cm. Carotid bifurcation is widened. There is high risk of cranial nerve injury with surgical resection.
surgical and non-surgical Treatment of carotid body tumors
- Biopsy is contraindicated due to risk of bleeding.
- Due to low but finite chance of malignancy, surgical resection is recommended. In good risk patients, resection before the tumor gets too big is advantageous.
- If surgical risk is high, such as in patients with contralateral cranial nerve dysfunction, radiation therapy should be considered.
- If patient is old, tumor is stable, and cranial nerve injury risk is high, you may consider doing nothing (monitor).
- Large tumors are well-vascularized by branches of external carotid artery, which is usually the ascending pharyngeal branch. Preoperative embolization of feeder vessels may decrease blood loss and tumor size. This is usually recommended by experts for Shamblin II and III tumors.
- Surgical resection can take place within 24 hours of embolization to minimal inflammatory response after embolization.
- Bipolar electrocautery is a must to decrease cranial nerve injury.
- There is approximately 5% risk of permanent cranial nerve injury, with 40% risk of temporary neurapraxia.
- Perioperative stroke risk is 1-2%. Mortality rate is <1%.