Bilateral subclavian arteries passing in front of the scalenus anterior muscles

Abstract

Herein, we present a very rare case of bilateral subclavian arteries passing in front of the scalenus anterior muscles in a cadaver. This abnormality was observed in a 73-year-old Japanese male cadaver during a dissection session for students in 2004 at Osaka Dental University. The bilateral scalenus anterior muscle originated from the anterior tubercle of the transverse processes of the fifth and sixth cervical vertebrae and inserted into the scalene tubercle of the first ribs. The right scalenus minimus muscle was observed, but no left scalenus minimus muscle was observed. The aortic arch was a type A according to Adachi's classification. The origin of the internal thoracic artery was distal to that of the thyrocervical trunk. The bilateral brachial plexuses was formed by the union of the ventral rami from the fifth cervical to the first thoracic nerves and passed between the scalenus anterior and the scalenus medius muscles. To our knowledge, such a case has not been reported previously.

Comparative study of the ramification patterns of the subclavian branches as the subclavian artery passes in front or behind the scalenus anterior muscle

“…The incidence of the subclavian artery passing in front of the scalenus anterior muscle in our study was 1.8% (2/112 sides); this is higher than the incidences reported in previous studies (Table 3) Ramification pattern of the subclavian branches as the subclavian artery passed in front of the scalenus anterior muscle In our two cases of the subclavian artery passing in front of the scalenus anterior muscle, the subclavian artery gave off the vertebral artery, costocervical trunk, thyrocervical trunk, and internal thoracic artery, in this order (type X). Uemura et al (2007Uemura et al ( , 2009 reported the same ramification pattern of the subclavian branches in three cases in which the subclavian artery passed in front of the scalenus anterior muscle. In comparison, we classified the ramification patterns of the subclavian branches as the subclavian artery passed behind the scalenus anterior muscles into six types (types A-F), none of which were the same as type X observed with anterior passage of the vessel.…”

“…Takafuji and Sato (1991) suggested that the mechanism of the abnormality was caused by the disappearance of the primordium of the scalenus anterior muscle and the remaining portion of the primordium of the scalenus minimus muscle, resulting in the subclavian artery passing in front of the scalenus muscle (developing scalenus minimus muscle). However, Uemura et al (2007) were able to observe the scalenus anterior, medius, posterior, and minimus muscles in the right side in their cases. They therefore concluded that the hypothesis of Takafuji and Sato (1991) was not applicable to this anatomical situation.…”

“…In only three of these 17 cases were the ramification patterns of the subclavian branches reported in detail. Uemura et al (2007Uemura et al ( , 2009 reported that the subclavian artery passing in front of the scalenus anterior muscle gives off the vertebral artery, costocervical trunk, thyrocervical trunk, and internal thoracic artery, in this order. These documented abnormalities led us to investigate the ramification patterns of the subclavian branches as the subclavian artery passes in front or behind the scalenus anterior muscle during student dissection practice sessions.…”

Prevertebral and Craniocervical Junction Muscles

“…The scalenus anterior was bilaterally inserted into the first rib (100%). Uemura et al (2007) revealed that the subclavian arteries passed in front of the scalenus anterior in 16 cases of 15 cadavers, including 2 cases from 2 fetuses. The incidence of this anomaly was reported to be less than 0.7% in adults; among the 14 unilateral cases, the incidence on right side was 18% (2 of 11 cases) and on the left 81.8% (9 of 11 cases); 3 were uncertain.…”

Bilateral anatomic variation in the relation of the upper trunk of the brachial plexus to the anterior scalene muscle

“…The BP is usually formed by three trunks: the upper trunk (UT) formed by the ventral rami of the C5 and C6 spinal nerves, the middle trunk -which is a continuation of the ventral ramus of the C7, and the inferior trunk formed by the ventral rami of the C8 and T1 [6,10]. The three trunks usually pass through the interscalene triangle -bounded anteriorly by the anterior scalene muscle (ASM), posteriorly by the middle scalene muscle (MSM) and inferiorly by the first rib [22]. The ASM arises from the transverse processes of the C3 to C6 vertebrae, and it inserts into the Lisfranc tubercle of the first rib, between the grooves for the subclavian artery (SA) and subclavian vein (SV).…”