Unilateral aberrant retropharyngeal internal carotid artery

Clinical History

A 47 years old woman with neck pain was admitted to emergency department after a traffic accident. Radiologic examinations revealed no abnormalities related to trauma but an abnormal vascular structure in retropharyngeal space. This was an incidental finding.

Imaging Findings

A patient complaining with neck pain, was admitted to the emergency department after a traffic accident. Physical examination revealed asymmetric retropharyngeal soft tissue bulging. Non-contrast computed tomographic (CT) images revealed no bone abnormalities related to trauma but widening of the retropharyngeal space was detected. Contrast -enhanced CT images showed that the enlargement of the retropharyngeal space was primarily due to an retropharyngeal course of the right internal carotid artery (ICA ). An magnetic resonance imaging (MRI) exam was required for the evaluation of the head trauma, and a sequential magnetic resonance angiography (MRA) was performed in order to further evaluate the vascular anatomy. The abnormal course of the cervical portion of the right ICA in the retropharyngeal space was clearly demonstrated; the vessel shifted medially almost to midline location and, then returned to its normal location before entering the skull base. The right common carotid bifurcation was at a higher level than the left one.

Discussion

The retropharyngeal space extends from the skull base to about the level of the sixth thoracic vertebral body. It is bounded posteriorly by the prevertebral fascia and anteriorly by the buccopharyngeal fascia. Normally, the retropharyngeal soft tissue space contains only fat and lymph nodes and their associated lymphatic channels. Causes of retropharyngeal soft-tissue widening may be hematoma, inflammatory processes such as abscess formation, benign and malignant neoplasms (mainly metastatic retropharyngeal adenopathies). An aberrant course of the ICA is a rare cause of retropharyngeal space enlargement. Some degree of aberrant course of cervical ICA tortuosity is found in 10 to 30 % of arteriogram especially in elderly patients. 67% of cases are unilateral on the right side and 31% are bilateral. The exact cause of the aberrant retropharyngeal course of ICA is unknown. Vascular tortuosity and atherosclerotic changes in elderly and hypertensive patients or a congenital origin have been suggested. Our patient was not hypertensive and had not any other atherosclerotic changes. Therefore, we believe it had a congenital origin or mixed mechanism in this patient. Most of the cases are asymptomatic. Sometimes, it can cause dysphagia. Awareness of this abnormality is important because of the possible risks such as massive bleeding or other catastrophic results during some surgical or interventional procedures. Radiological examination is important in the differential diagnoses of retropharyngeal masses before surgical intervention. Lateral cervical radiograph shows retropharyngeal soft-tissue widening. If vascular calcification is present, it can be recognized on lateral radiograph by the position of vessel in relation to the vertebrae. ICA transposition can be accurately diagnosed with CT or MRA. Three dimensional reconstructucted images can reveal the course and anatomical relationship of the vascular structures in a non-invasive manner. Radiologists and clinical physicians should be aware of the possibility of this unusual position of the carotid arteries. Radiologists should report and alert the clinicians about this anomaly, even if it is an incidental finding in asymptomatic patients.

Differential Diagnosis List

Final Diagnosis

Aberrant retropharyngeal course of the internal carotid artery

URL:	https://www.eurorad.org/case/4282
DOI:	10.1594/EURORAD/CASE.4282
ISSN:	1563-4086