Neuroradiology Case of the Week

Case 23

José A. Echeverri, MD, Francisco Garcia-Morales, MD
and Sven E. Ekholm, MD, PhD

Clinical Presentation: This 46-year-old man presented with dysphagia. There was no other significant past medical history. A neck and chest CT were requested for further evaluation.

Imaging Findings:

Figure 1: Scout view obtained for the Chest CT shows a right sided aortic arch (arrow).	Figure 2: The first branch of the ascending aorta is the left common carotid artery (CCA) (arrow).
Figure 3: The second branch is the right CCA (arrow).	Figure 4: The third branch is the right SCA (arrow).
Figure 5: Axial Image at the level of the right aortic arch shows a retroesophageal diverticulum (Diverticulum of Kommerell) (up-pointing arrow). The diverticulum produces mass effect over the esophagus (down-pointing arrow) with subsequent dysphagia.	Figure 6: Notice the origin of the aberrant left SCA artery from the diverticulum (arrow).
Figure 7: Left subclavian artery (arrow).	Figure 8: Left subclavian artery, giving off the left vertebral artery (arrows).
Figure 9	Figure 10
Figure 11	Figure 12
Figure 13
Figures 9-13: Vascular Ring: a left ductus arteriosus extends from the aortic diverticulum to the left pulmonary artery (arrows). There seems to be some flow within the ductus.

Diagnosis: Right aortic arch with aberrant left SCA and left ductus arteriosus.

Discussion:
    A right aortic arch with an aberrant left SCA is usually an incidental finding in asymptomatic adults [1,2]. It is rarely associated with cyanotic congenital heart defects, except if associated with a Tetralogy of Fallot. Although usually asymptomatic this anomaly may present in the adulthood as dysphagia, known as “dysphagia lusoria,” which means difficulty in swallowing caused by aortic root anomalies [3].
    The right aortic arch with aberrant left SCA is due to a regression of the fourth left aortic (branchial) arch, between the left CCA and the left SCA. The first branch of the right aortic arch will be the left CCA (Fig. 2), the second branch is the right CCA (Fig. 3) and the third is the right SCA (Fig. 4). The fourth branch is the left SCA, which originates from the junction of the right arch and the right descending aorta. This vessel will cross the midline from right to left between the esophagus and the thoracic spine (Fig. 6). Some patients have a large retroesophageal diverticulum (diverticulum of Kommerell) (Fig. 5), thought to be a remnant of the embryonic left arch, from which the left SCA arises (Fig. 6). The diverticulum of Kommerell is the result of the large blood flow through the fetal ductus arteriosus. The ductus arteriosus is on the left, arising from the aortic diverticulum, if present (Figs. 9-13), or from the left SCA. This combination of a right aortic arch and left ductus arteriosus forms a vascular ring [1,2,4].
    The combination of right aortic arch, aberrant left SCA and left ductus arteriosus is the most common type of right aortic arch anomaly where a vascular ring is formed around the esophagus [4].

References:

1. Spindola-Franco H, Fish BG, Abnormalities of the Great Arteries, In: Elliot LP ed. Cardiac Imaging in Infants, Children and Adults. Baltimore, MA; J.B. Lippincott Company; 1991; 344-368.
2. Dahnert W, Radiology Review Manual 2nd edition. Philadelphia, PA: Williams & Wilkins; 1993; 355-372.
3. Kettles DI, Latouf SE, Von Opell U: Dysphagia Lusoria. Clinical Cardiology 1999; 22: 751-753.
4. Amplatz K, Moller JH: Radiology of Congenital Heart Disease. St Louis, MO: Mosby; 1993: 995-1049.