Ultrasonographic anatomy of the brachial plexus and major nerves of the canine thoracic limb.

A technique for ultrasonography of the brachial plexus and major nerves of the canine thoracic limb is described based on examination of five canine cadavers and three healthy dogs. The ventral branches of the spinal nerves that contribute to the brachial plexus are identifiable at their exit from the intervertebral foramina. These nerves may be followed distally, cranial to the first rib, until they form the brachial plexus. The musculocutaneous, ulnar, and median nerves are identified on the medial aspect of mid-humerus and followed proximally to the axillary region and distally to the elbow. The radial nerve, formed by multiple nerve components, is seen on the mediocaudal aspect of the humerus. Nerves appear as hypoechoic tubular structures with an internal echo-texture of discontinuous hyperechoic bands, surrounded by a thin rim of highly echogenic tissue. Improved understanding of the ultrasonographic anatomy of the brachial plexus and its main branches supports clinical use of this modality.