Carotid body tumors (CBT) are rare tumor developed from the neural crest. Manifestations of the tumor are variable; mainly it presents as a asymptomatic mass having slow growth and compressing the surrounding anatomic structures, ¹ it can rarely cause syncope by compression of the peripheral nerves such as the vagus and cervical sympathetic nerve. ²

Syncope is characterized by loss of consciousness and falling, because of transient cerebral hypo perfusion. ³ We report three cases with CBT and recurrent syncope attacks and convulsive syncope. Their symptoms disappeared after surgical removal.

Case 1

A 78-year-old woman was admitted to Al-Zahra Hospital, Isfahan, Iran, in December 2010, because of episodic vertigo and attack of loss of consciousness when she was in a sitting position. These attacks were accompanied with perspiration, pallor and bradycardia and after a few seconds followed with colonic movement of left extremities. She regained consciousness after taking supine posture.

The past medical history was negative except for the history of toxoplasmosis 7 years ago; drug and family history were unremarkable. Neurological examination was normal in a lying position but when she was sitting she became pale, lost her consciousness and convulsive syncope happened. Electroencephalography (EEG) did not show any abnormal discharges, Brain magnetic resonance imaging (MRI) and computed tomography scan, Holter monitoring, echocardiography and coronary angiography were normal. Cervical MRA and digital subtraction angiography (DSA) revealed CBT Figure 1. Figure 1

Cervical MRI confirming the presence of a carotid body tumor

CBT arising from paraganglia has higher incidence in female than males and more common presenting in 50-70. ⁴

The pathogenesis of CBT remains uncertain but hypoxia and genetic factors are probable mechanisms. Some studies have shown that low pressure of oxygen in the blood and chronic hypoxia both continuously and intermittently due to living in high altitude and sleep apnea respectively, can precipitate carotid gland hyperplasia and hypertrophy. Genetic bases established in up to 35% of individual with CBT who have a higher occurrence of multiple ganglioneuroma in childhood if they experience chronic hypoxia. ⁵

A common manifestation of CBT is a slow-growing, painless mass in the neck, located anterior to the sternocleidomastoid muscle at the level of the hyoid bone that usually was found accidentally by patients or physicians. ⁶ Occasionally, a carotid pulse, bruit or thrill may be associated with the mass. ⁶ In rare instances carotid sinus syndrome is manifestation of CBT that is characterized by syncope and hypotension due to a hypersensitive carotid sinus located in the carotid bifurcation. ⁷ , ⁸ Actually, carotid sinus is a baroreceptor which is a collection of nerve ending that locates at the carotid bifurcation, regulates the cardiac rhythm and blood pressure. ⁷ Its compression, therefore, induces bradycardia, hypotension, repeated syncope and falling. ² Syncope is an important differential diagnosis for patients with recurrent loss of consciousness. Prolonged syncope can cause tonic movements and it has been shown that as a convulsive syncope ⁹ , ¹⁰ the prevalence of convulsive syncope is approximately 0.03%. ¹¹ Furthermore, seizure must be considered in recurrent episode of unconsciousness; Clinically, distinguishing between seizure and syncope is difficult, although the presentation of both conditions are the same, their pathophisiology are totally different; cerebral hypo perfusion marked in syncope does not happen in epilepsy because epilepsy is due to abnormal electrical activity. ¹¹

To the best of our knowledge, there are just a few cases reported by syncope and CBT, ² , ¹¹ , ¹² and recurrent convulsive syncope as presentation of carotid body is very rare. We had three patients with convulsive syncope and CBT, which were female.

CBTs is an infrequent cause of syncope, and convulsion is a rare presentation of syncope, so frequent happening of convulsive syncope and CBTs assume that convulsive syncope is more common in CBTs than other causes of syncope. In addition, the higher frequency in females increases probability for genetic base of this tumor, this hypothesis is supported by bilateral CBT in third case who is young, and based on previous report bilateral CBT more commonly occurring on familial basis. ¹³ Another hypothesis is that females are more sensitive to hypoxic events to improve CBT. Finally, the improvement of syncope by surgery suggested that CBTs is a reversible cause of syncope and that surgery could be a good therapeutic approach.

The gold standard for the diagnosis of CBTs is a DSA, another diagnostic way which can confirm the CBTs is Color Doppler Sonography. ⁶

Treatment of choice for CBTs is the surgical resection. ⁵ Surgical planning depends on the relation of the tumor to the internal carotid artery (ICA), so, degree of contact of the tumor with the ICA was used to classify the tumor radiologically into three types in an attempt to predict the Shamblin group of the tumors: Type I, less than or equal to 180°; type II, greater than 180° and less than 270°; and type III, greater than or equal to 270°, ¹³ based on this criteria all of our patients have had grade I CBT, If the tumor have small and still display.

Outlying involvement of the ICA, this needs to refer patients to the surgeon, because the small size may understand incorrectly to signify greater ease of resection. ¹⁴

Subsequently, in each patient with recurrent episodes of syncope, especially convulsive syncope CBT must be considered as a suspected treatable cause.