AJR 2002; 178:1269-1274
© American Roentgen Ray Society
Aberrant Subclavian Arteries
Cross-Sectional Imaging Findings in Infants and Children Referred for Evaluation of Extrinsic Airway Compression
Lane F. Donnelly1,
Robert J. Fleck1,2,
Preeyacha Pacharn1,3,
Matthew A. Ziegler1,
Bradley L. Fricke1 and
Robin T. Cotton4
1 Department of Radiology, Children's Hospital Medical Center, 3333 Burnet Ave.,
Cincinnati, OH 45229-3039.
2 Present address: Department of Radiology, Naval Medical Center, San Diego, CA
92134-1204.
3 Present address: Department of Radiology, Mahidol University, Bangkok,
Thailand 10700.
4 Division of Otolaryngology, Children's Hospital Medical Center, Cincinnati, OH
45229.
Received September 25, 2001;
accepted after revision November 16, 2001.
Address correspondence to L. F. Donnelly.
Abstract
OBJECTIVE. 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.
MATERIALS AND 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. All 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. Both 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.
Introduction
A 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]. A 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]. A 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. A 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
[2,3,4,5,6].
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 2000. All 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 (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]. All 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 superior 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. A midline descending aorta was defined as present when the
descending 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 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. Airway 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.
1A,1B,1C,1D,2A,2B,3A,3B).
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.
1A,1B,1C,1D,2A,2B,3A,3B).
All such patients had both Kommerell's diverticulum and midline descending
aorta resulting in the airway compression.
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Fig. 1A. —Right aortic arch with aberrant left subclavian artery
causing airway obstruction in 22-month-old girl. Axial T1-weighted MR image
shows right aortic arch (A). Aberrant 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.
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Fig. 1B. —Right aortic arch with aberrant left subclavian artery
causing airway obstruction in 22-month-old girl. Endoscopic image at same
level as A shows extrinsic posterior compression (arrows) of
trachea.
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Fig. 1C. —Right aortic arch with aberrant left subclavian artery
causing airway obstruction in 22-month-old girl. Axial T1-weighted MR image
shows compression of carina and proximal bilateral main bronchi
(arrows) associated with midline descending aorta (D).
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Fig. 1D. —Right aortic arch with aberrant left subclavian artery
causing airway obstruction in 22-month-old girl. Endoscopic image at same
level as C shows extrinsic compression of carina and main bronchi.
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Fig. 2A. —Right aortic arch with aberrant left subclavian artery
causing airway obstruction in 1-year-old boy. Axial 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).
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Fig. 2B. —Right aortic arch with aberrant left subclavian artery
causing airway obstruction in 1-year-old boy. Axial T1-weighted MR image at
more inferior level than A 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.
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Fig. 3A. —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 (A) and
aberrant left subclavian artery (arrowhead). Aberrant subclavian
artery is greater in diameter at its origin that it is more distally,
consistent with Kommerell's diverticulum (not shown).
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Fig. 3B. —Right aortic arch with aberrant left subclavian artery
causing airway obstruction in 11-month-old male infant. CT image at level of
lower airway shows compression of carina and proximal left main bronchus
(arrow) associated with midline descending aorta (D).
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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.
1A,1B,1C,1D).
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.
Airway compression was identified in five of these nine patients. In all five
patients, the airway compression was a the level at which the aberrant
subclavian artery crossed posterior to the trachea (Fig.
4A,4B,4C).
In the other four patients, no airway compression was identified. The five
patients with airway compression had findings confirmed at bronchoscopy (Fig.
4A,4B,4C).
Two of the five patients with airway compression were treated with tracheotomy
tube placement; the others were treated without surgical intervention.
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Fig. 4A. —Left aortic arch with aberrant right subclavian artery
causing airway compression in 2-year-old girl. Axial T1-weighted MR image
shows left aortic arch (A) and origin of aberrant right subclavian artery
(arrowhead). Trachea (arrow) is compressed.
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Fig. 4B. —Left aortic arch with aberrant right subclavian artery
causing airway compression in 2-year-old girl. Axial T1-weighted MR image
shows most marked compression of trachea (arrow) at level of aberrant
right subclavian artery (arrowhead).
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Fig. 4C. —Left aortic arch with aberrant right subclavian artery
causing airway compression in 2-year-old girl. Endoscopic image at same level
as A shows posterior extrinsic compression (arrows) of trachea
by aberrant right subclavian artery.
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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 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.
All 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.
A 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, occuring 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. Although 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. Alternatively, 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
[10,11,12].
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]. Both CT and MR imaging
have been reported useful in describing the anatomy associated with right
aortic arch and aberrant left subclavian artery
[2,3,4,5,6].
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.
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Abstract
Introduction
