Origin of the dorsal scapular artery and its relation to the brachial plexus in Thais.

We investigated the variations of the origin of the dorsal scapular artery (DSA) and its relation to the brachial plexus in 252 sides of the posterior cervical triangles of Thais. The origin of this artery on each part of the subclavian artery or other arterial branches was examined with special reference to their course in relation to the brachial plexus. The results show that the DSA originated from three sites; most commonly from the transverse cervical artery (69%) followed by the direct branching from the second (2.8%) or the third part (28.2%) of the subclavian artery. When the DSA was branched from the transverse cervical artery, its course was always posterior or above the brachial plexus. When the DSA arose from the second or the third part of the subclavian artery, it always ran in the branches of the brachial plexus in various sites. The most frequent course was to pass between the upper and middle trunks of the brachial plexus (63.2%). Other courses were far less frequent and found to pass between the anterior division of the upper trunk and the middle trunk of brachial plexus or between the roots of C8 and T1 with the frequency of 1.3 and 2.6%, respectively.