Introduction
The brachial plexus is a network of the anterior branches of the spinal nerves of vertebrae C5-Th1. This is another name for the lower four cervical vertebrae and the uppermost thoracic vertebra. This “arm plexus” belongs to the so-called peripheral nervous system, which lies outside the skull bone and the spinal canal and connects the central nervous system with the successful organs. At first glance, the brachial plexus appears very confusing and confusing. However, once the basic structure has been understood, in the case of brachial plexus paralysis, it is often possible to draw conclusions about the lesion of the affected nerve and the physician can therefore make a precise diagnosis.
Structure
The individual branches of the anterior spinal nerves of our plexus first join to form the so-called trunci (trunks), after which they pass through a triangular passageway for several conduction pathways, which in anatomical jargon is called the posterior scalenus gap. These 3 trunks (trunci) can be subdivided by their associated nerves: – the upper trunk: Truncus Superior (consisting of spinal nerve C5 and C6) – the middle trunk: Truncus Medius (consisting of spinal nerve C7) – the lower trunk: Truncus Inferior (consisting of C8 and Th1) At the transition to our axillary region, this part of the plexus is not called trunks but small bundles or packets. In Latin, the term fascicle is often used here.
These can be subdivided according to their position in relation to our axillary artery. – the lateral bundle: Fasciculus lateralis (consisting of spinal nerve C5 – C7) – the central bundle: Fasciculus medialis (consisting of spinal nerve C8 – Th1) – the posterior bundle: Fasciculus posterior (consisting of spinal nerve C5- Th1) Our infraclavicular branches often branch off from these, which then run to the shoulder muscles. These branches will be explained in more detail in the next section.
The course of these branches allows us to divide our brachial plexus into nerves that run below the clavicle and nerves that run above the clavicle. This is of great relevance, especially for a doctor’s diagnosis. Nerves that run above the clavicle: These nerves share their course with our axillary artery and have the following names: – N. dorsalis scapulae – N. thoracicus longus – N. suprascapularis – N. subclavius These nerves can be summarized under the name supraclavicular nerves. Nerves that run below the collarbone: Fasciculus lateralis (C5 – C7) N. musculocutaneus N. pectoralis lateralis N. medianus (Radix lateralis) Fasciculus medialis (C8-Th1) N. ulnaris N. pectoralis medialis N. cutaneus brachii medialis N. cutaneus antebrachii medialis Fasciculus posterior (C5-Th1) N. radialis N. axillaris N. subscapularis N. thoracodorsalis
