Congenital brachial plexus palsy

Dear Sir,

I read with interest the study by Tandon and Tandon (Tandon and Tandon 2005). I, however, would like to debate a few points: First, the authors state that there is little in the literature regarding factors, which increase the risk of obstetric brachial plexus palsy. In 2005, a literature review identified 10 articles which examined the risk factors of congenital brachial plexus palsy (CBPP): Three large studies examined the risk factors in the general population (numbers of cases included in these studies were 323, 1611 and 2399) and seven other studies examined the risk factors for CBPP in cases complicated by shoulder dystocia (Khunda and Tuffnell 2005). Second, keeping in mind that group 2 in their study included four women out of 27 who did not have shoulder dystocia, I find it difficult to justify the authors' conclusion ‘In the presence of similar neonatal variables, brachial plexus injury is more likely to occur in neonates of primiparous women in the presence of shoulder dystocia, if labour is augmented’. This may well have been the case if these four patients were excluded or if a sub-analysis was presented. Third, the authors use the posterior shoulder argument as evidence in support of the theory of maternal expulsive forces as a causative factor for CBPP in cases complicated by shoulder dystocia. I agree that this is likely to be so in most cases of posterior brachial plexus injuries, but would like to draw attention to two possible scenarios where traction on the head can lead to injury to the brachial plexus of the posterior shoulder:

1. Cases in which shoulder dystocia involves the posterior shoulder as well as the anterior shoulder and the delivery attendant applies upwards traction (or even more likely, downwards traction in case of delivery in all-fours position).

2. Cases in which the angle between the antero-posterior (AP) diameter of the head at delivery and its normal position in relation to the shoulders is more than 90° and the case is complicated by shoulder dystocia. This rare scenario can occur if the head enters the pelvis in an occipito-posterior position, but then rotates (more than 90°) to deliver in an occipito-anterior position. If the shoulders are then impacted at the pelvic entrance due to shoulder dystocia, they will not rotate to resume their normal position to the head, which on the other hand usually fails to restitute. If the delivery attendant is not mindful of this situation and does not act to correct the position of the head in relation to the shoulders or even worse rotates the head in the opposite direction, then downwards traction on the head will result in injury to the already stretched brachial plexus, which is attached to the uppermost side of the head at one end and to the posterior shoulder at the other end.