Aneurysm of an anomalous right subclavian artery.

An anomalous right subclavian artery arising from the left side of the aortic arch distal to the left subclavian artery was first described by Hunauld (1735). In most cases the artery passes behind the oesophagus to reach the right side of the neck. The defect is usually attributed to a failure of development of the fourth right aortic arch, the caudal part of the right dorsal aorta persisting, sometimes with dilatation, to form the proximal part of the abnormal right subclavian artery. There are numerous accounts of this anomaly and they have been reviewed by Cairney (1925). Symptoms are unusual but in a small proportion of cases dysphagia is complained of. Bayford (1789) termed the difficulty in swallowing dysphagia lusoria.