Relationship between Trachea, Brachiocephalic trunk and Vagus nerve among fetuses

Respiratory compromise due to tracheal compression by the Brachiocephalic trunk (BT), a condition labeled as Innominate Artery Compression Syndrome, has been attributed to an anomalous origin of this vessel to the left of, and hence crossing, the trachea. The aim of this study was to establish the normal relationship between the BT and trachea in 30 spontaneously aborted human foetuses between 14–35 weeks of gestation. In current study, in all the cases, BT origin was to the left of the trachea, and then crossed trachea from left to right finally dividing further into its branches i.e subclavian artery (SA) and right common carotid artery (RCCA). It was also observed that trachea was crossed over by BT at middle level in 65% fetuses, while in the remaining 35% BT crossed trachea at lower one third level. This finding has clinical significance as during any kind of vascular intervention through vessels of heart, there are more chances of injury to trachea or adjoining structures if it is being crossed over by BT at middle level, rather than at lower one third level. Diameter of RCCA and LCCA was observed to be 1.22 ± 0.88 mm and 1.67 ± 0.83 mm, respectively. Both vagus nerves were found to be lying at distance of 0.76 ± 0.22 mm from the trachea at middle level in 78% of the cases, while in rest of the cases, vagus nerve was found to be lying in close approximation to trachea at the level of middle one third. Thus, more precautions need to be taken during vascular surgeries or tracheostomies in neonates, so as to avoid damage to the vagus nerve