Aberrant Right Subclavian Artery, An Unusual & Less Identified Cause of Dysphagia “Dysphagia Lusoria”A Case Report on Imaging Findings

Dysphagia, or difficulty swallowing, is a common clinical symptom that often prompts an extensive evaluation. While many causes of dysphagia are well recognized, such as malignancies or structural abnormalities of the esophagus, there exists a rare and often overlooked cause – the aberrant right subclavian artery (ARSA). This congenital anomaly can result in compression of the esophagus, leading to what is known as Dysphagia lusoria. In this article, we delve into a case report of a 38-year-old male with this unusual diagnosis and explore its clinical presentation, imaging findings, and management strategies.

Understanding Dysphagia Lusoria

Dysphagia lusoria refers to difficulty in swallowing due to compression of the esophagus by an abnormal right subclavian artery. The term "lusoria" originates from the Latin phrase “lusus naturae,” meaning "freak of nature," which aptly describes the unusual anatomical course of the artery.

The condition was first described by Bayford in 1761, when he reported a case of a 62-year-old female patient with long-standing dysphagia that ultimately led to her death. Aberrant right subclavian artery is the most common congenital abnormality of the aortic arch, occurring in approximately 0.5% to 1.7% of the population. Despite this relatively frequent occurrence, the condition often goes undiagnosed as about two-thirds of patients with ARSA are asymptomatic.

Pathophysiology of ARSA

In a normal aortic arch, the right subclavian artery arises as the first branch of the aortic arch, supplying blood to the right upper limb. However, in patients with ARSA, the artery takes an aberrant path, arising as the fourth branch of the aortic arch, distal to the left subclavian artery. Instead of originating on the right side of the body, it crosses from left to right behind the esophagus in approximately 80% of cases, causing compression of the esophagus and leading to dysphagia.

In some cases, the artery's path is located between the esophagus and trachea, or even in front of the trachea, but these instances are rarer. Compounding this condition is the possible development of atherosclerosis or aneurysmal dilation of the artery in elderly patients, exacerbating the esophageal compression and leading to more pronounced symptoms.

Case Report: A 38-Year-Old Male with Progressive Dysphagia

A 38-year-old male presented to the hospital with a three-month history of progressively worsening dysphagia, specifically for solid and semisolid foods. He had also experienced significant weight loss. Initial evaluations, including an upper gastrointestinal endoscopy, were negative for mechanical causes of dysphagia, such as strictures or masses.

Due to the persistence of his symptoms, the patient was referred for an esophagogram, an imaging test that uses contrast to evaluate the structure and function of the esophagus.

Esophagogram Findings

The esophagogram revealed a fixed narrowing of the esophagus at the level of the aortic arch. The narrowing was noted to run from inferior left to superior right, involving the posterior aspect of the esophagus, a pattern highly suggestive of an ARSA. The esopha-gogram's anterior-posterior (AP) view showed the contrast being held up by an external mass near the aortic arch, further supporting the suspicion of an aberrant artery.

To confirm the diagnosis, a CT aortic angiogram was performed, which demonstrated the presence of an ARSA arising from the distal aortic arch. The artery was seen crossing behind the esophagus, exerting significant pressure on the postero-lateral esophageal wall, thus explaining the patient's dysphagia. Additionally, a pouch-like aneurysmal dilatation of the proximal portion of the artery, known as a diverticulum of Kommerell, was identified.

Morphological Types of ARSA

ARSA can present in several morphological patterns. Based on the Adachi-Williams classification, there are three types:

Type I (Type G) – Four branches in the sequence of right common carotid artery (RCCA), left common carotid artery, left subclavian artery, and ARSA.

Type II (Type CG) – Similar to Type I, but with an additional left vertebral artery branch arising between the left common carotid artery and left subclavian artery.

Type III (Type H) – Three branches, including the bicarotid trunk (a common trunk of both carotid arteries), left subclavian artery, and ARSA.

In this case, the patient demonstrated a Type II morphology of ARSA.

Clinical Discussion

The most common causes of dysphagia in adults include malignancy, esophageal motility disorders, and strictures. Dysphagia lusoria, caused by ARSA, is a rare but notable cause of organic dysphagia. Despite being the most common congenital anomaly of the aortic arch, ARSA often goes unrecognized in clinical practice due to its non-specific symptoms.

The condition occurs due to the involution of the fourth vascular arch and the right dorsal aorta during embryonic development, leaving the seventh intersegmental artery attached to the descending aorta. In some patients, the ARSA originates with a broad base, known as Kommerell's diverticulum, which can further complicate the clinical picture by causing more severe compression of the esophagus.

Diagnosis and Management

Dysphagia lusoria can be challenging to diagnose. Esophago-gastrod-uodenoscopy (EGD) is often negative in approximately 50% of cases, as the esophageal compression is extrinsic. In such cases, imaging studies play a crucial role. Barium swallow studies, such as the esophagogram used in this case, can demonstrate the characteristic indentation on the posterior esophageal wall caused by ARSA. However, CT angiography and chest MRI are the best diagnostic modalities, as they allow for precise visualization of the vascular anatomy and help guide treatment planning.

For symptomatic patients, management depends on the severity of the dysphagia and its impact on nutrition. In mild cases, dietary modification and symptomatic treatment may be sufficient. However, for patients with significant weight loss or intractable symptoms, surgical intervention may be required. Surgical options include resection and ligation of the aberrant artery, sometimes with the placement of an endovascular prosthesis.

Conclusion

Dysphagia lusoria is a rare but important diagnosis to consider in patients with unexplained dysphagia, especially when other more common causes have been ruled out. Advanced imaging techniques, such as CT angiography, are critical for identifying ARSA and planning appropriate interventions. Early recognition and management of this condition can significantly improve patient outcomes, particularly for those with severe symptoms.