Anatomical Science International (2007) 82, 180–185 doi: 10.1111/j.1447-073x.2006.00162.x CaseBlackwell Publishing Asia Report Bilateral subclavian arteries passing in front of the scalenus anterior muscles* Mamoru Uemura, Akimichi Takemura and Fumihiko Suwa Department of Anatomy, Osaka Dental University, Osaka, Japan 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. Key words: abnormalities, gross anatomy, scalenus anterior muscle, scalenus minimus muscle, subclavian artery. Introduction acute cardiac insufficiency. The length and diameter of the blood vessels and size of the muscles were Herein, we present for the first time a very rare case measured with calipers. We investigated the incidence of bilateral subclavian arteries passing in front of the of this case in 318 cadavers (636 sides) studied in scalenus anterior muscles in a cadaver; this was dis- dissection sessions for students at our facilities in covered during a dissection session for students in the period 1994–2004. 2004 at Osaka Dental University. There are few reports The protocol for the present research did not include of the abnormalities concerning the course of the any specific issue that needed to be approved by subclavian artery. To our knowledge, no case of bilateral the ethics committees of our institutions. The present subclavian arteries passing in front of the scalenus work conformed to the provisions of the Declaration anterior muscles has been reported. Adachi (1928) of Helsinki in 1995 (as revised in Edinburgh 2000). and seven others (Mori, 1941; Komatsu et al., 1984; Inuzuka, 1989; Takafuji & Sato, 1991; Okamoto et al., Results 1997; Kodama, 2000; Yuda et al., 2000) have reported 14 cases of a unilateral subclavian artery passing in Right side front of the scalenus anterior muscle. Right subclavian artery Case Report The brachiocephalic trunk (16.2 mm in diameter) bifurcated into the right subclavian artery (12.0 mm The present case was observed in a 73-year-old in diameter) and the right common carotid artery Japanese male cadaver. The cause of death was an (8.1 mm in diameter). The right subclavian artery arose from the brachiocephalic trunk at a level with the middle of the third thoracic vertebra, ran super- *This study was presented at the 110th Annual Meeting of olaterally and sequentially branched first into the the Japanese Association of Anatomists (Toyama, Japan) right vertebral artery (4.0 mm in diameter), the right 29–31 March 2005. costocervical trunk (2.0 mm in diameter) and the Correspondence: Mamoru Uemura, Department of Anatomy, Osaka Dental University, 8-1 Kuzuhahanazono-cho, right thyrocervical trunk (3.2 mm in diameter) supe- Hirakata-shi, Osaka 573-1121, Japan. riorly, and then into the right internal thoracic artery Email: [email protected] (3.0 mm in diameter) inferiorly. In addition, the artery Received 6 June 2006; accepted 20 July 2006. passed in front of the right scalenus anterior muscle © 2006 Japanese Association of Anatomists and behind the right subclavian vein, and shifted Subclavian A. & scalenus anterior M. 181 Figure 1. Photograph (a) and schematic illustration (b) showing the anterior view of the subclavian arteries (su) and the scalenus anterior muscles (SA). aa, aortic arch; ac, ascending cervical artery; av, axillary vein; ax, axillary artery; bc, brachiocephalic trunk; br, brachial plexus; cc, common carotid artery; bv, brachiocephalic vein; co, costocervical trunk; C5–8, the fifth–eighth cervical nerves; CV4–7, vertebral body of the fourth–seventh cervical vertebrae; ds, descending scapular artery; E, esophagus; ij, internal jugular vein; it, internal thoracic artery; L, lung; LC, longus colli muscle; LO, longus capitis muscle; lt, lower trunk of the brachial plexus; mt, medial trunk of the brachial plexus; ph, phrenic nerve; R, first rib; S, scalenus minimus muscle; SM, scalenus medius muscle; SP, scalenus posterior muscle; sc, superficial cervical artery; ss, suprascapular artery; sv, subclavian vein; T, trachea; T1, the first thoratcic nerve; TV1, vertebral body of the first thoracic vertebra; tc, transverse cervical artery; ty, thyrocervical trunk; ut, upper trunk of the brachial plexus; va, vagus nerve; vc, superior vena cava; ve, vertebral artery; asterisk, diverticulum. towards the right axillary artery (8.0 mm in diameter) right scalenus anterior muscle. It originated from the at the lateral margin of the right first rib. The right anterior tubercle of the transverse process of the axillary artery passed between the seventh cervical seventh cervical vertebra and inserted into the right nerve (C7) and C8 of the brachial plexus. first rib at the posterior region of the scalenus anterior The right vertebral artery entered the transverse muscle tail. It was innervated by C8 (Figs 1,2). foramen of the sixth cervical vertebra. The right cos- tocervical trunk bifurcated into the right deep cervical Right brachial plexus (1.8 mm in diameter) and the right supreme intercostal The right brachial plexus was formed by the union arteries (1.9 mm in diameter). The right thyrocervical of the ventral rami from C5 to the first thoracic nerve trunk sequentially branched into the right descending (Th1). The upper (C5 and C6), middle (C7) and lower scapular (2.0 mm in diameter), the right superficial trunks (C8 and Th1) passed between the scalenus cervical (2.0 mm in diameter), the right ascending anterior and the scalenus medius muscles and cervical (2.2 mm in diameter) and the right inferior towards the axillary fossa and the humerus. No thyroid (2.0 mm in diameter) arteries. The right abnormalities were found in the trunks (upper, suprascapular artery (2.0 mm in diameter) arose from middle and lower) or the cords (medial, lateral and the right axillary artery (Figs 1,2). posterior; Figs 1,2). Right scalenus anterior muscle and the scalenus Left side minimus muscle The right scalenus anterior muscle (length 71.7 mm; Left subclavian artery width of muscle head 7.7 mm; width of muscle belly The left subclavian artery (18.6 mm in diameter at 11.4 mm; width of muscle tail 8.4 mm) originated the region where it branches from the aortic arch) from the anterior tubercle of the transverse processes arose superolaterally from the superior wall of the of the fifth and sixth cervical vertebrae and inserted aortic arch. A diverticulum was found near its origin. into the scalene tubercle of the right first rib. The This artery sequentially branched into the left vertebral muscle was innervated by C6 and C7. artery (4.0 mm in diameter), the left costocervical The right scalenus minimus muscle (length trunk (2.0 mm in diameter) and the left thyrocervical 42.5 mm; width of muscle head 8.6 mm; width of trunk (4.0 mm in diameter) superiorly and the left muscle belly 7.2 mm; width of muscle tail 5.0 mm) internal thoracic artery (3.4 mm in diameter) inferiorly. was observed to be located posterolaterally to the In addition, the artery passed in front of the left © 2006 Japanese Association of Anatomists 182 M. Uemura et al. Figure 2. Photograph (a) and schematic illustration (b) showing the anteroinferolateral view of the right subclavian artery (su) and the right scalenus anterior muscle (SA). aa, aortic arch; ac, ascending cervical artery; av, axillary vein; ax, axillary artery; bc, brachiocephalic trunk; br, brachial plexus; cc, common carotid artery; bv, brachiocephalic vein; co, costocervical trunk; C5–8, the fifth–eighth cervical nerves; CV4–7, vertebral body of the fourth–seventh cervical vertebrae; ds, descending scapular artery; E, esophagus; ij, internal jugular vein; it, internal thoracic artery; L, lung; LC, longus colli muscle; LO, longus capitis muscle; lt, lower trunk of the brachial plexus; mt, medial trunk of the brachial plexus; ph, phrenic nerve; R, first rib; S, scalenus minimus muscle; SM, scalenus medius muscle; SP, scalenus posterior muscle; sc, superficial cervical artery; ss, suprascapular artery; sv, subclavian vein; T, trachea; T1, the first thoratcic nerve; TV1, vertebral body of the first thoracic vertebra; tc, transverse cervical artery; ty, thyrocervical trunk; ut, upper trunk of the brachial plexus; va, vagus nerve; vc, superior vena cava; ve, vertebral artery; asterisk, diverticulum. scalenus anterior muscle and behind the subclavian vical (2.1 mm in diameter) and the left inferior thyroid vein and shifted towards the left axillary artery (1.7 mm in diameter) arteries. The left suprascapular (7.4 mm in diameter) at the lateral margin of the artery (2.0 mm in diameter) arose from the left axillary left first rib. The left axillary artery ran in front of artery (Figs 1,3). the left brachial plexus without passing through the plexus. Left scalenus anterior muscle The left vertebral artery entered the transverse The left scalenus anterior muscle (length 76.6 mm; foramen of the sixth cervical vertebra. The left cos- width of muscle head 12.0 mm; width of muscle belly tocervical trunk bifurcated into the left deep cervical 8.5 mm; width of muscle tail 13.0 mm) originated (1.8 mm in diameter) and the left supreme intercostal from the anterior tubercle of transverse processes of arteries (2.0 mm in diameter).