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Left mainstem bronchial narrowing: a vascular compression syndrome? Evaluation by magnetic resonance imaging
R G Hungate1, B Newman, M P Meza
1Department of Radiology, Children's Hospital of Pittsburgh and University of Pittsburgh Medical Center, 3705 Fifth Avenue, Pittsburgh, PA 15213, USA.
Insights
Vascular compression of the left mainstem bronchus (LMSB) is more common in children with an anteriorly positioned descending aorta (DA). This finding suggests a link between aortic position and LMSB narrowing in pediatric patients.
Area of Science:
- Pediatric Radiology
- Thoracic Surgery
- Pediatric Pulmonology
Background:
- Vascular compression of the left mainstem bronchus (LMSB) by the descending aorta (DA) and pulmonary artery (PA) is a suspected cause of LMSB narrowing in children.
- Anatomical relationships in affected children have not been compared to those with a normal LMSB.
Purpose of the Study:
- To compare the anatomical relationships of the LMSB, DA, and PA in symptomatic children with LMSB narrowing to those in asymptomatic children.
- To evaluate the utility of MR imaging in defining LMSB narrowing.
Main Methods:
- Retrospective review of medical and radiologic records of 10 symptomatic children (1-19 months) with MR-demonstrated LMSB narrowing.
- Comparison with 40 asymptomatic control children (1 week-19 months) without great vessel or bronchial abnormalities on MR.
- Detailed chest MR evaluation of airway and great vessel anatomy, focusing on LMSB course and relationship to DA and PA, including DA position relative to the spine.
Main Results:
- Symptomatic children showed a statistically significant trend toward a more anteriorly positioned descending aorta (DA) at the level of the LMSB compared to controls (P < 0.05).
- The pulmonary artery (PA) segment was anterior to the LMSB more often in symptomatic children (RPA/bifurcation) than controls (LPA).
- MR imaging demonstrated LMSB narrowing with excellent correlation to bronchoscopy in 90% of symptomatic cases.
Conclusions:
- While an anterior DA position can be a normal variant, it is more prevalent and pronounced in children with LMSB narrowing.
- Vascular compression of the LMSB between an anteriorly displaced DA and the PA is a significant factor in symptomatic LMSB narrowing in children.
Background And Objective:
Vascular compression of the left mainstem bronchus (LMSB) between the descending aorta (DA) and pulmonary artery (PA) has been suggested as a cause for LMSB narrowing in children. These anatomic relationships have not been compared with those in children with a normal LMSB. Materials and methods. We undertook a retrospective review of the medical and radiologic records of 10 symptomatic young children (1-19 months, 5 boys, 5 girls) with MR demonstration of LMSB narrowing and compared them to 40 young children without great vessel or bronchial abnormality on MR (1 week-19 months, 28 boys, 12 girls). Chest MR evaluation included assessment of airway and great vessel anatomy with specific attention to the course of the LMSB and its relationship to the adjacent DA and PA. The position of the DA in relation to the spine was carefully evaluated.
Results:
Five children had focal and five had diffuse LMSB narrowing. DA position at the level of the crossing LMSB: in 40% of symptomatic children the DA was located in front of the adjacent vertebral body; in 40%, 1/2-3/4 and in 20% 1/4-1/2 of the circumference of the DA was located anterior to the spine. In the control group, the DA was prespinal in 10%, with a trend toward a more paraspinal location of the DA. The trend toward a difference in position of the DA between symptomatic and control patients was statistically significant (P < 0.05). DA position was not related to age (up to 19 months). At the level where the LMSB crossed the DA, a segment of the PA was located anterior to the LMSB, more often the right PA (RPA) or pulmonary bifurcation in symptomatic children and the left PA (LPA) in controls. No correlation was apparent between length of LMSB narrowing and DA or PA position. Chest radiographic abnormalities, when present, were subtle. Excellent MR/bronchoscopic correlation of LMSB narrowing was found in nine of the ten symptomatic children. One child underwent posterior aortopexy and ligation of the ligamentum arteriosum.
Conclusion:
LMSB narrowing is well-defined by MR imaging. While a prespinal position of the DA occurs in some children as a normal variant, it is more common and more marked in children with LMSB narrowing. Vascular compression of the LMSB between an anteriorly positioned DA and the pulmonary artery appears to be important in children with symptomatic LMSB narrowing.