Aberrant Subclavian Arteries: Cross-Sectional Imaging Findings in Infants and Children Referred for Evaluation of Extrinsic Airway Compression

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1 Lane F. Donnelly 1 Robert J. Fleck 1, 2 Preeyacha Pacharn 1, 3 Matthew. Ziegler 1 radley L. Fricke 1 Robin T. Cotton 4 Received September 25, 2001; accepted after revision November 16, Department of Radiology, Children s Hospital Medical Center, 3333 urnet ve., Cincinnati, OH ddress correspondence to L. F. Donnelly. 2 Present address: Department of Radiology, Naval Medical Center, San Diego, C Present address: Department of Radiology, Mahidol University, angkok, Thailand Division of Otolaryngology, Children s Hospital Medical Center, Cincinnati, OH JR 2002;178: X/02/ merican Roentgen Ray Society berrant Subclavian rteries: Cross-Sectional Imaging Findings in Infants and Children Referred for Evaluation of Extrinsic irway Compression OJECTIVE. The purpose of our study was to describe patterns of airway compression identified on cross-sectional imaging in infants and children with either right aortic arch and aberrant left subclavian artery or left aortic arch with aberrant right subclavian artery. MTERILS ND METHODS. Data from MR imaging and CT performed to evaluate pediatric patients for extrinsic airway compression were reviewed for cases that revealed an aberrant right or left subclavian artery. Clinical, endoscopic, and imaging findings in identified cases were reviewed. Recurrent patterns of extrinsic compression were reviewed among cases. RESULTS. Twelve patients with right aortic arch with aberrant left subclavian artery and nine patients with left aortic arch and aberrant right subclavian artery were identified. ll 12 with right aortic arch with aberrant left subclavian artery had airway compression shown, with multiple sites or diffuse compression in six. Of these 12 patients, nine had compression at the level of the arch and aberrant subclavian artery (10 had Kommerell s diverticulum), and nine had compression of the distal airway in association with a midline descending aorta. Five of the nine patients with left aortic arch and aberrant right subclavian artery had airway compression shown, all at the level of the arch and aberrant subclavian artery. None of these compressions was associated with either Kommerell s diverticulum or midline descending aorta. CONCLUSION. oth right and left aberrant subclavian arteries can be associated with symptomatic airway compression, but the patterns of compression are different. The airway compression in right aortic arch with aberrant left subclavian artery is often associated with either Kommerell s diverticulum or midline descending aorta, whereas compression associated with left aortic arch and aberrant right subclavian artery is not. left aortic arch with aberrant right subclavian artery is the most common congenital arch anomaly, followed by right aortic arch with aberrant left subclavian artery [1]. right aortic arch and associated aberrant left artery can be associated with a left ligamentum arteriosum that forms a complete vascular ring and leads to airway compression [1]. left aortic arch with aberrant right subclavian artery has been described as not being associated with airway compression [1]. We have encountered both aberrant left and right subclavian arteries in pediatric patients referred for cross-sectional imaging in the evaluation of airway symptoms. number of case reports have revealed the capability of MR imaging or CT to show the anatomic findings of aberrant subclavian artery with or without an associated Kommerell s diverticulum [2 6]. However, to our knowledge, no articles have described the cross-sectional imaging findings in a series of children with aberrant subclavian artery who were referred for cross-sectional imaging because of suspected extrinsic airway compression. The purpose of this study was to review a series of children referred for cross-sectional imaging for airway symptoms to identify those who had airway compression associated with aberrant subclavian artery and to describe anatomic patterns of airway compression. Materials and Methods CT and MR imaging performed to evaluate for extrinsic airway compression were reviewed for cases in which either a right aortic arch with aberrant left subclavian artery or a left aortic arch with an aberrant right subclavian artery were present. MR imaging studies were reviewed from a 5-year period from 1996 through ll MR imaging studies were performed on a 1.5-T scanner (General Electric Medical Systems, Milwaukee, WI) with sequences including at minimum T1-weighted images in the axial, sagittal, and coronal planes. CT examinations were reviewed from a 1-year period from 1999 to 2000, after the installation of a multidetector CT scanner JR:178, May

2 Donnelly et al. (LightSpeed, General Electric Medical Systems). CT studies were obtained after the administration of IV contrast material. CT parameters included 2.5-mm slice thickness, 120 kvp, and weight-based, low-dose tube current [7]. ll patients were referred from our otolaryngology department for evaluation of potential lower airway compression. Symptoms included stridor or noisy breathing, with or without chronic or recurrent lower respiratory tract infection. In some of the patients, cross-sectional imaging was ordered after endoscopic evaluation revealed findings of extrinsic airway compression. Patient charts and imaging studies were reviewed in identified cases. The age, sex, and clinical presentation of the patients were recorded. It was noted whether the patient was evaluated with MR imaging or multidetector CT. The imaging findings reviewed included the presence of airway narrowing and, if present, the supe- rior to inferior level of airway narrowing (at the level of the aberrant subclavian artery, aortic arch, distal trachea, carina, or main bronchi). The presence of a right aortic arch with an aberrant left subclavian artery or left aortic arch with an aberrant right subclavian artery was recorded. The presence of a Kommerell s diverticulum and, if present, its contribution to airway compression were noted. Kommerell s diverticulum is defined as a dilatation of the proximal portion of an aberrant subclavian artery near the origin from the aorta. In our review, Kommerell s diverticulum was considered present when the measurement of the diameter of the subclavian artery near its origin from the aortic arch was at least twice the size of its diameter more distally. We noted whether a midline descending aorta was present and, if it was, whether the midline descending aorta contributed to airway compression. midline descending aorta was defined as present when the de- C scending aorta was anterior to the vertebral bodies, rather than in the normal, paravertebral location [8]. Recurrent patterns of extrinsic compression were reviewed between cases. In patients who had undergone bronchoscopy, imaging findings were compared with findings seen on bronchoscopy. We noted whether a patient underwent surgical treatment and, if so, what type of surgery was performed. The retrospective review of this material was approved by our institutional review board. Results We identified 21 patients who had undergone cross-sectional MR imaging or CT to evaluate potential extrinsic airway compression and who had aberrant subclavian arteries. The study population included 13 males and eight D Fig. 1. Right aortic arch with aberrant left subclavian artery causing airway obstruction in 22-month-old girl., xial T1-weighted MR image shows right aortic arch (). berrant left subclavian artery (arrowheads) is larger at its origin than more distally, consistent with Kommerell s diverticulum. Trachea (arrow) is severely compressed at this level., Endoscopic image at same level as shows extrinsic posterior compression (arrows) of trachea. C, xial T1-weighted MR image shows compression of carina and proximal bilateral main bronchi (arrows) associated with midline descending aorta (D). D, Endoscopic image at same level as C shows extrinsic compression of carina and main bronchi JR:178, May 2002

3 Imaging of Infants and Children with berrant Subclavian rteries females, ranging in age from 7 weeks to 12 years (mean age, 2 years 3 months). Thirteen of the patients were 1 year old or younger. Fifteen patients had undergone MR imaging and six had been examined by CT. Of the 21 patients, 12 had a right aortic arch with aberrant left subclavian artery, and nine had a left aortic arch with aberrant right subclavian artery. Of the 12 patients with a right aortic arch and aberrant left subclavian artery, 10 had Kommerell s diverticulum, nine had midline descending aorta, and one had a cervical arch. irway compression was seen in all 12 patients. The airway was compressed at the level of the arch and aberrant subclavian artery in nine patients. In all of these nine patients, the Kommerell s diverticulum contributed to the airway compression. The airway was compressed at the level of the distal airway in nine patients (carina in eight, left main bronchus in one) as a result of compression from the midline descending aorta (Figs. 1 3). In these patients, the descending aorta was in an abnormal midline location immediately anterior to the spine, rather than in the normal paraspinal location. The abnormal position of the descending aorta was associated with abnormal stacking of structures from anterior to posterior in the confined space between the anterior chest wall and the spine. The stacking in this confined space resulted in compression of the distal airway between the abnormally positioned descending aorta posteriorly and the pulmonary arteries anteriorly [8]. In the 10 patients with associated Kommerell s diverticulum, nine had airway compression at the level of the Kommerell s diverticulum. The two patients without a Kommerell s diverticulum had airway compression distally, related to a midline descending aorta. In six patients, the airway was compressed in multiple areas or in a continuous long segment of airway (Figs. 1 Fig. 2. Right aortic arch with aberrant left subclavian artery causing airway obstruction in 1-year-old boy., xial T1-weighted MR image shows aberrant left subclavian artery with mild compression of trachea (arrow). Proximal subclavian artery is dilated consistent with Kommerell s diverticulum (arrowhead)., xial T1-weighted MR image at more inferior level than shows compression of carina (arrows) associated with midline descending aorta (D). Degree of compression at level of midline descending aorta is more severe than that at level of Kommerell s diverticulum. Fig. 3. Right aortic arch with aberrant left subclavian artery causing airway obstruction in 11-month-old male infant., CT image through upper airway shows compression of trachea (arrow) at level of arch () and aberrant left subclavian artery (arrowhead). berrant subclavian artery is greater in diameter at its origin that it is more distally, consistent with Kommerell s diverticulum (not shown)., CT image at level of lower airway shows compression of carina and proximal left main bronchus (arrow) associated with midline descending aorta (D). JR:178, May

4 Donnelly et al. 3). ll such patients had both Kommerell s diverticulum and midline descending aorta resulting in the airway compression. In 11 of the 12 patients with a right aortic arch and aberrant left subclavian artery, the airway compression was confirmed at bronchoscopy as a pulsatile extrinsic compression at the described anatomic regions (Fig. 1). One patient did not undergo bronchoscopy. Nine of the 12 patients underwent surgical division of the ligamentum arteriosum; all of these patients subsequently had marked improvement or complete resolution of airway symptoms. One patient was treated with tracheotomy tube placement alone. Two patients who had less severe degrees of narrowing at imaging were treated conservatively. None of the nine patients with a left aortic arch and aberrant right subclavian artery had Kommerell s diverticulum or a midline descending aorta. irway compression was identified in five of these nine patients. In all five patients, the airway compression was at the level at which the aberrant sub- clavian artery crossed posterior to the trachea (Fig. 4). In the other four patients, no airway compression was identified. The five patients with airway compression had findings confirmed at bronchoscopy (Fig. 4). Two of the five patients with airway compression were treated with tracheotomy tube placement; the others were treated without surgical intervention. Discussion Children who present with airway symptoms such as a combination of stridor, apnea, cyanosis, or recurrent infection may be referred for cross-sectional MR imaging or CT for evaluation of potential extrinsic airway compression. In this review of children referred for cross-sectional imaging to exclude extrinsic airway compression, we identified patients with right aortic arch with aberrant left subclavian artery and with left aortic arch with aberrant right subclavian artery with associated airway compression. However, the patterns of airway compression and the treatment of these two groups of children were different. The presence of a right aortic arch and aberrant left subclavian artery is related to an interruption of the left aortic arch between the left common carotid and left subclavian arteries [1]. The presence of a left ligamentum arteriosum completes the vascular ring in most such patients; however, it is reported that only 5% of these patients have associated airway symptoms [1]. Patients who present with airway symptoms have been found to have an associated large Kommerell s diverticulum or tight ligamentum arteriosum with the airway compression at the level of the Kommerell s diverticulum, the aortic arch, or both [1]. In our study, anatomic variations associated with airway compression were more variable. The presence of a Kommerell s diverticulum was one of two anatomic variations associated with airway compression. The other anatomic variant was midline descending aorta. In nine of 10 patients with Kommerell s diverticulum, we found compression at the level of the arch Fig. 4. Left aortic arch with aberrant right subclavian artery causing airway compression in 2-year-old girl., xial T1-weighted MR image shows left aortic arch () and origin of aberrant right subclavian artery (arrowhead). Trachea (arrow) is compressed., xial T1-weighted MR image shows most marked compression of trachea (arrow) at level of aberrant right subclavian artery (arrowhead). C, Endoscopic image at same level as shows posterior extrinsic compression (arrows) of trachea by aberrant right subclavian artery. C 1272 JR:178, May 2002

5 Imaging of Infants and Children with berrant Subclavian rteries and aberrant subclavian artery. However, in one patient with a Kommerell s diverticulum, no associated airway compression was seen at that level. In an equal number of patients with right aortic arch and aberrant left subclavian artery leading to compression at the level of the aberrant subclavian artery, we found compression of the distal airway (carina or main bronchi) remote in location from the arch and Kommerell s diverticulum. This distal compression cannot be explained by the presence of a tight ring at the level of the arch and subclavian artery or Kommerell s diverticulum alone. These patients all had an associated abnormal midline position of the descending aorta. Midline descending aorta was first described as a potential cause of airway compression in 1995 [8]. Other investigators then found that a midline position of the descending aorta was more often present in children with left main bronchus compression than in nonsymptomatic patients [9]. Normally, the descending aorta sits in a paraspinal location. When the descending aorta lies immediately anterior to the spine, abnormal stacking of structures occurs in the confined space between the spine and the anterior chest wall. In such patients, the distal airway most typically the carina or left main bronchus is extrinsically compressed between the abnormally positioned descending aorta posteriorly and the pulmonary arteries anteriorly [8]. Midline descending aorta airway compression syndrome has been described as an isolated lesion [8], but it has also been reported to occur as a secondary phenomena as seen with hypoplastic right lung and resultant mediastinal shift or with a right aortic arch and left sided descending aorta [10]. The presence of a right aortic arch and aberrant left subclavian artery may be associated with an increased incidence of a midline descending aorta. ll nine patients in our study who were treated by division of the ligamentum arteriosum had marked improvement or complete resolution of airway symptoms after surgery, despite the anatomic variations associated with airway compression that were found among them. Therefore, it is likely that both the compression of the trachea related to a Kommerell s diverticulum and the compression of the distal airway related to a midline descending aorta are dependent on the presence of the left ductus arteriosum causing a tight ring. patient with a right aortic arch and aberrant subclavian artery can have airway compression associated with a number of anatomic factors. The presence of compression of the distal airway remote from the arch and Kommerell s diverticulum does not mean that these patients are not candidates for division of the ligamentum arteriosum, because these patients also seem to respond to surgical division of the ligamentum arteriosum. The most common congenital anomaly of the aortic arch is a left aortic arch with an aberrant right subclavian artery, occurring in approximately one in 200 people [1]. It is reported that the right ductus arteriosum almost always disappears; therefore, this arch anomaly is not associated with a vascular ring. It is common teaching that left aortic arch with an aberrant right subclavian artery is not associated with symptomatic airway compression [1]. However, in our series of patients referred for cross-sectional imaging because of airway symptoms suggesting compression, nine patients had left aortic arch with an aberrant right subclavian artery. Of these, five had cross-sectional imaging findings of compression of the trachea at the level of the arch and aberrant subclavian artery, and all were confirmed at bronchoscopy. These findings suggest that the presence of a left aortic arch with an aberrant right subclavian artery can be associated with airway compression. The anatomic patterns associated with airway compression in the patients with aberrant left subclavian artery differed from those of patients with right aortic arch and aberrant left subclavian artery. None of the patients with aberrant right subclavian artery had either an associated Kommerell s diverticulum or a midline descending aorta. lthough two of these patients did require tracheotomy, unlike the patients with right aortic arch and aberrant left subclavian artery, none of the patients with airway compression related to an aberrant left subclavian artery underwent surgery aimed at relieving the compression. Possibly patients with left aortic arch and aberrant right subclavian artery have less severe symptoms, although the symptoms in many patients were severe enough to warrant both cross-sectional imaging and bronchoscopy. lternatively, the care-providing physicians may have been reluctant to treat airway compression caused by a left aortic arch with an aberrant right subclavian artery, because airway compression has not been described in such patients. We recognize that the referral pattern for the patients images in this study predisposed to identify those with airway compression. Most children with left aortic arch and aberrant right subclavian artery are likely asymptomatic. This review was not designed to compare the capability of CT or MR imaging to depict extrinsic airway compression associated with aberrant subclavian artery. MR imaging has traditionally been the imaging modality of choice in evaluating these patients [10 12]. However, with the recent increases in speed of acquisition, helical CT has begun to play an increasingly larger role in the evaluation of these patients [12]. oth CT and MR imaging have been reported useful in describing the anatomy associated with right aortic arch and aberrant left subclavian artery [2 6]. Of the 21 patients in our study, six were evaluated on CT and 15 were evaluated on MR imaging. These numbers reflect the practice patterns over the past 5 years at our institution. We found both examinations to be adequate in depicting the findings in these patients. Multidetctor CT has the advantage of rapid imaging, which reduces the need for sedation in patients with compromised airways [13]. In conclusion, airway compression can occur with both right aortic arch and aberrant left subclavian artery and with left aortic arch and aberrant right subclavian artery. However, the patterns of compression are different. With an aberrant left subclavian artery, compression may be at the level of the right aortic arch and aberrant subclavian artery, often associated with a Kommerell s diverticulum. Compression of the distal airway associated with a midline descending aorta may also be present. In distinction, aberrant left subclavian artery is not associated with either Kommerell s diverticulum or midline descending aorta, and the airway compression is typically at the level of the arch and aberrant subclavian artery. References 1. Strife JL, isset GS III, urrows PE. Cardiovascular system. In: Kirks DR, ed. Practical pediatric radiology, 3rd ed. Philadelphia; Lippincot- Raven, 1998: oyagi S, kashi H, Tayama K, Fujino T. neurysm of aberrant right subclavian [corrected] artery arising from diverticulum of Kommerell: report of a case with tracheal compression. Eur J Cardiothorac Surg 1997;12: enedikt R, Jelinek JS, Schaefer PS, Edwards F, Ghaed V. 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