Patterns of Thyrocervical Trunk Variation

Abstract

This study reports the classification of thyrocervical trunk branching patterns from 64 subclavian arteries in 33 adult cadavers. Of the 64 subclavian arteries, 28 (43.8%) were from male cadavers and 36 (56.3%) were from female cadavers. Branching patterns were classified based on a scheme described by Lippert and Pabst.1 A thyrocervical trunk was observed 63 times in the sample and was absent on one side in one cadaver; two cadavers had one side that was unusable due to previous dissections. In all cadavers that had a thyrocervical trunk, branching occurred at the subclavian artery distal to the vertebral artery and medial to the anterior scalene muscle. The incidence of the traditional thyrocervical trunk branching pattern described in textbooks (type a), in which the thyrocervical trunk is formed by the inferior thyroid, suprascapular, and transverse cervical arteries, was 64.1% (36.6% male, 63.4% female). The incidence of the next most common pattern (type c), in which the inferior thyroid and suprascapular arteries branched from a common trunk and the transverse cervical artery had a separate origin, was 21.9% (71.4% male, 28.6% female). The incidence of the third most common pattern (type b), in which the internal thoracic artery originated from the thyrocervical trunk in addition to the inferior thyroid, suprascapular, and transverse cervical arteries, was 6.3% (20.0% male, 80.0% female). Four other subclavian arteries had different branching patterns, including one that had no thyrocervical trunk. The cadaver with no thyrocervical trunk exhibited the inferior thyroid, suprascapular, and transverse cervical arteries arising separately from the subclavian artery.Chi‐square analyses comparing male and female distribution samples, as well as comparing right and left sides, yielded no significant differences for either. However, comparisons between the frequency of branching patterns in this study with those reported by Lippert and Pabst revealed a significant difference between the two samples (p<.05). While Lippert and Pabst reported the incidence of types a and c at 30% each, this study reports the incidence of those types at 64.1% and 21.9%, respectively. The cadaver with no thyrocervical trunk and separate arteries arising from the subclavian artery was not described in the extensive study by Lippert and Pabst, and perhaps may be a rare variant.This region of the body is a common site of invasive procedures; therefore, it is critical to be aware of common and variable arterial branching patterns.Support or Funding InformationThis study was made possible with the support of the Chicago College of Osteopathic Medicine and Midwestern University.