The rare origin of the suprascapular artery arising off the internal thoracic artery in the presence of the thyrocervical trunk : clinical and surgical implications

Anatomical textbooks usually cite the thyrocervical trunk, which arises from the first part of the subclavian artery, as the most common origin of the suprascapular artery [1, 2]. Variations concerning the origin of the suprascapular artery are rare but have been documented arising from all three parts of the subclavian artery, the costocervical trunk, the axillary artery, and the internal thoracic artery (often called the internal mammary artery by clinicians) [3 – 7]. The suprascapular artery can also be duplicated bilaterally or even absent [6]. Two separate case reports even noted the suprascapular artery taking origin from the dorsal scapular artery [8, 9]. Origin of the suprascapular artery from the internal thoracic artery has been documented during comprehensive studies of the subclavian artery and its branches [3, 4, 7]. The rate of this occurrence varies, however, the authors do not mention if these unusual origins took place in the presence of the thyrocervical trunk. In 1905, Bean noted this variant in 12 of his 104 cases (11.5%); however, most studies report a lower incidence for this variant origin, including Read and Trotter (4.2%), DeGaris (2.2%), Coulouma and Van Varseveld (5.0%), Thomson (1.8%), Adachi (4.3%), and recently Takafuji and Sato (4.2%) [4, 6]. In 2005, Weiglein et al. reported the suprascapular artery as arising from trunks called the “cervico-scapular, dorsoscapular, and cervico-dorso-scapular trunks” [10]. The cervico-scapular trunk contains the superficial cervical and suprascapular arteries. The dorso-scapular trunk contains the dorsal scapular and the suprascapular arteries. The cervicodorso-scapular trunk contains the superficial cervical, dorsal scapular, and the suprascapular arteries [10]. There were two cases of duplicate suprascapular arteries existing bilaterally [6]. The first suprascapular artery followed its most common pattern but the second suprascapular artery originated from the third part of the subclavian artery, was transfixed to the brachial plexus, and ultimately passed under the suprascapular ligament [6]. The occurrence of a subligamentous suprascapular artery has been extensively studied [9, 11, 12], and a 1999 study by Yücel et al. reported the incidence of the suprascapular artery traveling through the suprascapular notch in 2.5% of cases [13], including one case where the suprascapular artery arose from the third segment of the subclavian artery [14]. In 2009, Reineck and Krishnan reported three individual cases of the suprascapular artery passing through the suprascapular notch during arthroscopic suprascapular nerve release [15]. Interestingly, their clinical incidence of 3% closely correlates with studies reported in cadaveric Stavros ATSAS Jacob N. FOX H. Wayne LAMBERT