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Findings: The CT scan shows an abnormal course of the left internal carotid artery. The carotid arteries have extensive atherosclerotic changes in them. The bifurcation of the left carotid artery and the left internal carotid artery are situated medial to their normal location in the posterior pharynx. The left internal carotid courses medially across the posterior pharyngeal area, causing the apparent mass. There is no other abnormality detected in the neck.
Diagnosis: : Abnormal tortuosity of the internal carotid artery presenting as a pharyngeal mass.
Discussion: Tortuosity or looping of the internal carotid artery is common in the elderly. This is secondary to loss of arterial wall elasticity due to atherosclerosis and hypertension. Embryologically, the internal carotid artery is derived from a coiled third aortic arch and the dorsal aortic root. Failure to uncoil in the embryo results in a congenital tortuosity. This tortuosity can later become more pronounced in the elderly.
In this patient, the condition is unilateral and the extent of displacement of the left internal carotid artery is considerable. Atherosclerotic changes are seen in the carotids bilaterally. Taking both these factors into consideration, the condition is most likely a combination of congenital tortuosity with an added component of atherosclerosis.
An early study by Kelly, of the aberrant carotid arteries showed that the female:male sex ratio was 3:2. In 71% of cases the anomaly was bilateral and 63% occurred on the right side. The aberrant internal carotid artery is usually found adjacent to the lateral pharyngeal wall. The posterior presentation of the aberrant vessel near the midline is rare.
Most often the anomaly is silent, and picked up incidentally. The major clinical significance of the aberrant internal carotid artery is that the posterior pharyngeal mass should not be mistaken for a solid mass. This may create a situation where the clinician may try to biopsy the posterior pharyngeal mass. It can also cause hemorrhage following tonsillectomies and adenoidectomies. The significance of a tortuous internal carotid artery in cerebral insufficiency is controversial. Some consider it as a potential cause for cerebral and retinal embolization.
References:
Miller S et al. "Aberrant internal carotid artery presenting in the midline
retropharyngeal space: case report". Can Assoc Radiol J; 48(1) 33-37, 1997.
Shankar L, et al. "High-resolution computed tomography of an aberrant internal
carotid artery". J Otolaryngol; 21(5) 373-375, 1992.
Hertzanu Y, Tovi F. "Radiology case of the month. Aberrant internal carotid
artery manifesting as a pharyngeal mass". J Otolaryngol; 21(4) 294-296, 1992.
Kelly AB. "Tortuosity of the internal carotid in relation to the pharynx".
J Laryngol Otol; 40 15823, 1925.
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