The brachial plexus: Basic anatomical and functional considerations

✍ Scribed by Prof. Dr. J. M. G. Kauer

• Publisher: John Wiley and Sons
• Year: 1995
• Tongue: English
• Weight: 344 KB
• Volume: 16
• Category: Article
• ISSN: 0738-1085
• DOI: 10.1002/micr.1920160105

✦ Synopsis

T h e upper extremity receives its motor and sensory nerve supply from the spinal nerves C5-C8 and T1. The anterior rami of these nerves-often with contributions from C4 and T2-intermingle and are realigned in the brachial plexus, thus forming peripheral nerves with multisegmental contents. The fourth cervical anterior ramus usually gives a branch to C5, and T2 branches to T1. A large contribution from C4 accompanies a small contribution or absence of a contribution of T2. This forms the prefixed type of brachial plexus. The postfixed type is a plexus with only a small or absent contribution of C4 and a large contribution from T2.

The anterior rami of the spinal nerves are the roots of the brachial plexus; they intermingle into a variable plexiform formation. As a result the peripheral nerves that originate from the plexus have multisegmental contents. The process of dividing and rearranging nerve fibres continues in the more distal parts of the upper extremity with a marked interindividual variable outcome. Kerr has described the left-right intraindividual variability of the brachial plexus. ' Kaplan and Spinner have demonstrated the immense variability in the way the anterior rami of the spinal nerves form the plexus. Connections between peripheral nerves can also be viewed in this way: the median nerve-ulna nerve connection of Martin-Griiber in the forearm3 and the Riche-Cannieu median nerve-ulnar nerve connection in the hand.4

BRACHIAL PLEXUS ANATOMY

The first step in the plexus formation is the concentration of anterior rami of a number of spinal nerves into three trunks: the superior trunk ((25, C6), the middle trunk (C7), and the inferior trunk (C8, TI). Secondly, and shortly following, the trunks divide into anterior and posterior parts. The anterior parts hold the nerve fibres to the ventral compartments of the upper arm, the lower arm, and the hand.