An Absent Subscapular Artery Co-Existing with Multiple Variants of the Brachial Plexus and Clinical Implications.

Abstract

Knowledge of neurovascular variants in the upper limb is important to neurologists in explaining unusual neurological presentations, to trauma surgeons in the selection of appropriate surgical interventions, and to neuroradiologists in the interpretation of images. Here we present the case of an absent subscapular artery coexisting with multiple variants of the brachial plexus nerves in the left limb of a 71-year-old female cadaver. The median nerve was formed from 3 roots, 2 contributed by the lateral cord and one from the medial cord. The thoracodorsal branch shared a common trunk of origin with the lateral thoracic artery, while the circumflex scapular arose directly from the axillary artery. The musculocutaneous nerve did not penetrate the coracobrachialis muscle, but coursed superior to the second lateral root, and about the proximal and middle third of the brachium supplied the flexor arm muscle, continuing distally as the lateral cutaneous nerve of the forearm. The first lateral root coursed initially within the medial root proximally, exiting about 3 cm distally before travelling superolaterally to join the second lateral root. Final formation of the median nerve was in the distal third brachium. There is uniqueness in this median nerve formation; a variant or a reverse of Le Minor Type 2 was observed except that this lateral root joined the medial root initially, unlike in Type 2 in which the medial root joins the musculocutaneous nerve, both re-exiting to join in median nerve formation. Clinically, unexplained sensorimotor deficits in the flexor compartments distal to the elbow may be explained by inadvertent ligation to any of these median nerve roots.