The Ring-and-Sling complex – Does it “Ring” true?

Abstract

Background: The “Ring-and-Sling” complex (RSC) comprises congenital tracheal stenosis and an abnormal origin/course of the left pulmonary artery. Based on clinical and imaging studies, the luminal narrowing is assumed to be as a result of rings cartilage (forming an “O”). Aims: This is a postmortem based study of tracheal histology in infants after an autopsy encounter of a case of RSC. Subject and Methods: RSC was identified in an infant at autopsy. The tracheal histomorphology revealed the presence of cartilaginous plates (instead of rings) and fibro-elastotic proliferation at the site of trachealis muscle. These changes prompted a study on variations in the histology of the trachea (with no known anomaly) in 35 autopsied neonates and infants. The transverse sections of the trachea were taken at one or more levels (Level 1 – at the level of the thyroid, Level 2 – midway between the thyroid and the carina, and Level 3 – just above the carina. Statistical Analysis: Epi-info software (v1.4.3, CD, US). Results: On histology, 83 sections showed the trachealis muscle on the posterior aspect. A single semicircular cartilage was identified in only 17 of the 83 sections studied (20.5%, 6 in level 1, 9 in level 2 and 2 in level 3). In the remaining 66 sections (79.5%), the cartilage was disposed as multiple plates, ranging in number from 2 to 10. No significant association was found between semicircular cartilage rings and age, sex, gestational age, and level of section (P < 0.05). However, 14 cases with sectioning at all three levels were taken into account; all levels showed more cartilaginous plates compared to single rings, which were more common at level 1 (P > 0.05). Conclusions: The “ring” in RSC and normal infantile tracheas show cartilage plates with intermittent semicircular cartilage rings. These findings may have surgical implications for tracheal anomalies and bode favorable surgical outcomes.