Erb's palsy without shoulder dystocia

The purpose of this commentary is to review certain articles which have provided evidence that Erb's palsy can occur without associated shoulder dystocia. The mechanism of the specific cause of the injury will be described.

Prior to the last 10-12 years it was assumed that Erb's palsy occurred exclusively with and was the result of shoulder dystocia. Gonik et al. [Am J Perinat 1991;8:31-34], reported on a research study based on the premise that when Erb's palsies occurred there must have been shoulder dystocia present but it went undetected by the delivering physician. Subsequently Gherman [Am J Obstet Gynecol 1998;178:423-427], published a detailed study which carefully looked at multiple aspects of shoulder dystocia including those similar injuries occurring with and without associated shoulder dystocia.

Both Gonik's and Gherman's research revealed distinct maternal and newborn differences when comparing Erb's palsy occurring with and without associated shoulder dystocia. These differences, which have nothing to do with the ability to recognize shoulder dystocia, provide conclusive evidence that Erb's palsy does occur without associated shoulder dystocia.

Therefore, Gonik's original premise, that shoulder dystocia must have been present if Erb's palsy occurred, is not supported. This brings into question the cause of Erb's palsy in those cases without shoulder dystocia. The maternal forces are the most likely cause both with and without shoulder dystocia.