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Clinical Information: The patient is a 19 month old female recently adopted from the Ukraine with a history of multiple upper respiratory infections and a positive PPD (negative chest film, pt is on Isoniazid). She now presents with stridor. Radiographic Findings: 1. ESOPHAGRAM/BARIUM SWALLOW 2. MRI CHEST Note that the patient has a normal left-sided aortic arch. As it courses from the heart, the first vessel off the aortic arch is the right common carotid artery. Follow its path to the right neck. Next is the normal take-off of the left common carotid and left subclavian arteries. The fourth vessel off the aortic arch is the aberrant right subclavian artery. You can trace its course posterior to the esophagus and trachea as it continues on to the right upper extremity. Note that there is no brachiocephalic trunk/Inominate artery since its two branches are accounted for. The trachea and carina have no apparent narrowing on these films so the patient's stridor is not fully understood. Impression: The posterior notching on the esophagram is classic for an aberrant right subclavian artery. However you must also consider a right-sided aortic arch, and double aortic arch in the differential. The MRI is the definitive study and clearly defines the normal left sided aortic arch and aberrant right subclavian artery. Discussion: An aberrant right subclavian artery is the most common congenital vascular anomaly of the aortic arch, with an incidence of 1:200 in the general population. It typically arises just distal to the left subclavian artery and passes posterior to the mediastinum on its way to the right upper extremity. This artery, along with the anterior aorta creates a vascular ring around the mediastinal structures. Rarely, the aberrant subclavian artery will pass between the trachea and esophagus. A right aberrant subclavian artery is most often asymptomatic; however, it has the potential for impinging on the structures in the mediastinum. If present, impingement is usually picked-up in early childhood between 3 weeks to 2 years. The child may be wheezy or stridorous while awake and asleep, with symptoms worsening during activity. If extreme, it can result in cyanosis and feeding difficulties. Dyphagia caused by aortic root abnormalities is termed "dysphagia lusoria" derived from Latin lusus naturae, freak of nature. Radiographically, it is often an incidental finding on esophagram where it causes the classic "posterior notch" on lateral view. On plain PA/AP chest films, it may cause a widened mediastinum silouette. The mediastinum is often difficult to evaluate on the young child due to the size of the thymus. An MRI is considered the definitive study to fully define the course of the vessels off the aortic arch. Occasionally, the aberrant artery arises from a diverticulum of the aortic arch known as the "Diverticulum of Kommerell." Turbulent blood flow within the diverticulum may result in thrombosis. In addition, aneurysmal deterioration of the aberrant right subclavian artery may occur and involve the origin from the aorta. Aneurysms are associated with dyspnea, dysphagia, and upper extremity ischemia, and may occasionally rupture, requiring surgery. It is important to note that an aberrant right subclavian artery is associated with a number of syndromes including Dubowitz's, VCFS (Velo-Cardio-Facial), Down's, DiGeorge's, and Edward's syndromes and many types of congenital heart disease. In the case presented above, this patient had developmental delays. An MRI of her head showed mild ventriculomegaly (which may not be significant), and the remainder of the exam were normal. References:
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