Abdominal Origins of Shoulder Pain

C3-4-5 KEEPS THE DIAPHRAGM ALIVE…KIND OF!

First year anatomy taught us this little rhyme, but a recent review by Fernandez-Lopez et al (1) reminds us of some important lessons.

First of all, anatomy is INDIVIDUAL; while we generally share the same structures, variations are more common than we are taught. In their review, Fernandez-Lopez et al cited that 20% of the time the phrenic nerve may originate solely from the brachial plexus (C5-T1). As well, more than a third of people may have an accessory phrenic nerve originating from the subclavian nerve while others may have a “phrenicosuprascapular communication”.

The authors also illuminate the importance of the interconnectedness of the body structures. The phrenic nerve is not only motor to the diaphragm (a powerful connection between thorax and abdomen and associated myofascial links in itself) but also that its sensory afferent fibers include pericardial, pleural and parietal peritoneum sub diaphragmatically. Thus, in some instances, shoulder pain may be referred from abdominal surgery, both laparoscopy and cesarean section, due to chemical, metabolic, mechanical or vascular irritation of peripheral phrenic nerve endings and sensory motor neurons originating from the same level both ipsilaterally and contralaterally.

From a treatment perspective, the importance of treating the whole person including neuro, metabolic, myofascial/MSK and prioritizing scars cannot be overstated. As well, the power of the diaphragm, breathing and its influence is wide spread. So, if you are having difficulty resolving shoulder pain of ‘unknown’ origin, don’t forget to look for referred pain causes.

Fernandez-Lopez I, Pena-Otero D, Atin-Arratibel M, Eguillor-Mutiloa M. Influence of the phrenic nerve in shoulder pain: A systematic review, International Journal of Osteopathic Medicine 36 (2020) 36-48.