Why is the brachial plexus important?
The brachial plexus is a bundle of nerves that start from the spinal cord in the cervical portion of the spine and continue branching to feed the whole arm. These nerves are responsible for innervating all of the muscles of the arm, contributing to our feelings of sensations in the arm, as well as innervating muscle movement.
The brachial plexus is an anatomical structure that often comes up around pain, sometimes shoulder, neck, or hand and wrist pain. It’s an important structure to be aware of as it can interact with muscle tension to present a variety of symptoms of sensation, like pain, tingling, or numbness. In more extreme cases, pressure on the brachial plexus can cause the neurogenic (related to nerves) type of thoracic outlet syndrome. That happens when the space between the clavicle and the first rib is reduced to the point that compression on the brachial plexus, as it comes through the thoracic outlet, causes symptoms like pain, tingling, and/or numbness in the shoulders and neck, and possibly even the arm and/or fingers.
Where is the brachial plexus?
Generally, the nerves of the brachial plexus come out from the cervical spine between the anterior and middle scalene muscles to run over the first and second rib and under the clavicle. They then run deep to the pectoralis minor muscle and continue to branch as they feed various parts of the arm. The specific path of the nerves in the brachial plexus have some variability from person to person (Golarz, 2020; Leijnse et al., 2019).
Why is the brachial plexus sometimes associated with pain or tingling?
The path of the nerves that make up the brachial plexus provide many opportunities for either bony structures or muscles to put pressure on these nerves. Bony structures like the cervical vertebrae, the clavicles, and sometimes even the upper ribs, can put pressure on the nerves of the brachial plexus. Pressure can also be put on these nerves by short or tight muscles, like pectoralis minor or the scalenes. Pressure from tight muscles or bony structures on these nerves can cause those symptoms we mentioned earlier: pain, tingling, numbness, and other nervy sensations.
Golarz, Scott. 2020. Anatomic variation of the phrenic nerve and brachial plexus encountered during 100 supraclavicular decompressions for neurogenic thoracic outlet syndrome with associated postoperative neurologic complications. Annals of Vascular Surgery. 62:1615-5947.
Leijnse, J.N., B.S. de Bakker, and K. D’Herde. 2019. The brachial plexus - explaining its morphology and variability by a generic developmental model. Journal of Anatomy. doi:10.1111/joa.13123.