Erb's Palsy Without Shoulder Dystocia
ABSTRACT & COMMENTARY
Synopsis: Cases of Erb's palsy occurring without shoulder dystocia may result from a different process than those resulting after shoulder dystocia and might be due to in utero forces applied before delivery.
Source: Gherman RB, et al. Am J Obstet Gynecol 1998;178:423-427.
To determine whether brachial plexus injury and Erb's palsy occurring without documented shoulder dystocia differs from those cases resulting after shoulder dystocia, these investigators studied 40 cases of Erb's palsy over one year. Gherman and associates defined shoulder dystocia as " . . . the need for ancillary obstetric maneuvers other than gentle downward traction after delivery of the fetal head." Nearly half of the cases (17) occurred without identification of shoulder dystocia in the patient's hospital record, while 23 were associated with shoulder dystocia. Only two cases of Erb's palsy associated with shoulder dystocia persisted for more than a year and, therefore, were considered permanent. In contrast, more than 40% of those occurring without evidence of shoulder dystocia were persistent. Other clinical features characteristic of brachial plexus injury in the absence of documented shoulder dystocia were a second stage of less than 15 minutes, a higher incidence of clavicular fracture, increased involvement of the posterior arm, a longer time to resolution of the brachial plexus injury, and a significantly lower birth weight (3561 g as compared to 4805 g in cases associated with shoulder dystocia). Gherman et al conclude that cases of Erb's palsy occurring without shoulder dystocia may result from a different process than those resulting after shoulder dystocia and might be due to in utero forces applied before delivery.
COMMENT BY STEVEN G. GABBE, MD
Shoulder dystocia complicates approximately one in 200 deliveries and results in permanent brachial plexus injury in 1-5% of these cases. These injuries usually occur in multiparous patients delivering a macrosomic infant, often after a prolonged second stage in association with an operative vaginal delivery and, often, in pregnancies complicated by diabetes mellitus. The anterior shoulder is frequently involved as a result of forces applied during flexion of the head in an effort to deliver the infant. Over the years, there have been reports of brachial plexus injury occurring in the absence of shoulder dystocia. In fact, this injury has been reported in association with Caesarean delivery. Gherman et al now describe 40 cases of Erb's palsy occurring in vertex-presenting fetuses delivered vaginally. In 17 cases, shoulder dystocia was not documented. One might argue that shoulder dystocia had occurred but was not described in the chart. However, a review of 10 recently published series supports the conclusion that Erb's palsy can occur without trauma at delivery. Perhaps the injury results from impaction of the posterior shoulder on the sacral promontory. Regardless of the etiology, this information may prove to be of importance in the defense of malpractice cases that frequently follow deliveries associated with a brachial plexus injury.
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