The current report describes a rare bilateral aberrant SPSA originating from the AA 1st part (left side) and from the dorsal scapular artery (right side, the accessory vessel from the duplicated SPSA). The SPSA variant origin from the subclavian artery is more common (10 and 12%) [18, 20], compared to the rare axillary origin (incidence ranging between 1.6% and 3.8%) [12, 14, 17]. Naidoo et al. [14] reported an axillary origin of the SPSA (from the 1st part in 2% bilaterally, from the 2nd part in 5% unilaterally). Other SPSA unusual origins include the internal thoracic artery (1–11%), the inferior thyroid artery (3.84%) [7], the costocervical trunk (1%) [17, 18, 20], the subclavian artery 1st part (1–2 mm lateral to the internal thoracic artery, a high origin) [5] and the dorsal scapular artery [17]. Bilateral aberrant origins from the AA 3rd part (distal origins) are rare [7, 11, 16], as well as the SPSA distal origin from the subscapular artery, with the artery passing inferior to the superior transverse scapular ligament [1]. The subclavian origin of the SPSA, proximal to the internal thoracic artery, is challenging to dissect, and may cause postoperative ischemia [6]. Ferreira [7] described a SPSA duplication, with the accessory SPSA forming an anastomosis with the main SPSA, as in the current case. Moreover, in the current case, the SPSA atypically coursed at the left side between the brachial plexus lateral and medial cords, while at the right side its course was typical, anterior to the brachial plexus, like in the majority of the published cases (71%) [3]. The SPSA atypically courses between the brachial plexus upper and middle trunks in 28% and posterior to the brachial plexus in 1% [3]. The SPSA typically passes over the superior transverse scapular ligament [18]. Its course inferior to the ligament is rare (2.5%) [19]. In the present case both suprascapular artery and nerve terminated inferiorly to the superior transverse scapular ligament, at the left side.
Developmentally, the main vessels derive from a primary capillary plexus. Under prevailing conditions, some vessels enlarge and reach their definite form and others regress [2]. During that process, the variant branching pattern, including both the variant origin and/or course, may appear. The current report highlights the coexistence of a bilateral aberrant SPSA of atypical course and termination (unilaterally), a SPSA duplication (unilaterally), with five LTAs, a subscapular artery divided into multiple branches, a double MCN and a double lateral root of the median nerve (unilaterally). In addition, the ectopic branches coexisted with the absence of other AA branches, such as the superior thoracic artery. The accessory LTAs emanated from both the AA and the subscapular artery. In the literature, variant LTA origins include the thoracoacromial artery (67.62%), the AA (17.02%), the thoracodorsal artery (5%) and the subscapular artery (3.93%) [10]. The LTAs multiplication (3.09%), as well as its variant origin are clinically important [10] since the artery should remain intact during neck and breast surgery [10]. The formation of common trunks among the AA branches is quite uncommon. The subscapular artery has been identified to originate in common with the LTA (28.7%), with the posterior circumflex humeral artery (15.2%), and with the LTA and posterior circumflex humeral artery (4.7%) [8]. In the present study, the accessory LTAs emerged both from the AA and the subscapular artery, similarly to Panagouli et al. [15] case, in which the LTA emerged from the subscapular artery. The abnormal origin, course and termination of the AA branching pattern may cause confusion in angiographic studies and complicate a surgery [3]. In the current study, the main MCN had a typical course and branching pattern, while the accessory one innervated both coracobrachialis and the biceps brachii short head. In Miller and Trelease study [13], the duplicated MCN supplied the muscles of the anterior arm compartment and provided lateral antebrachial cutaneous innervation.
The SPSA is clinically important during surgery in the anterior neck and supraclavicular region and must be identified and ligated [9]. The artery’s injury may cause micro-embolic events at the suprascapular nerve small vessels leading to neuropathy [7]. The knowledge of the SPSA variants is clinically important in arthroscopic suprascapular nerve decompression and in management of glenohumeral region disease [12]. The meticulous knowledge of the origin and course of possible SPSA variants is of paramount importance [9]. The SPSΑ course below the superior transverse scapular ligament (into the fibro-osseous tunnel) adjacent to the suprascapular nerve can reduce the amount of the surface area, exerting pressure on the nerve, causing neural microtrauma, and resulting in neuropathy [19].