The role of electromyography in the management of the brachial plexus palsy of the newborn

Abstract

Despite being the foremost examination in the management of traumatic nerve damage electromyography (EMG) has an uncertain and ill-defined role in the investigation of brachial plexus palsy of the newborn (BPPN). This may be because EMG, which is used most commonly several months after birth, fails to answer adequately two of the most important questions posed by this condition: its aetiology and the likely prognosis. In this review, we contend that EMG has important contributions to the solution of both of these questions but only if the timing of the investigation is altered. Used early on in the first few days after birth, EMG can separate the rare palsies that occurred during the intrauterine period from those caused by events at the time of birth, and thus have an important role in directing the investigations of the aetiology more appropriately. EMG alone would still not be able to determine which of the perinatal events were responsible. If the EMG is then repeated before reinnervation complicates interpretation, it seems probable that it would identify accurately those cases, where neurotmesis and avulsion have occurred, much earlier than 3 months of age, the crucial age in the clinical assessment of BPPN for consideration for surgery. This might have very important implications for the future directions of treatment.

Introduction

It would be safe to say that Clinical Neurophysiology in general, and electromyography (EMG) in particular, has a rather chequered past in the management of brachial plexus palsy of the newborn (BPPN). Many centres do not use it at all and of those that do, few enthuse about it. EMG is the premier investigative technique for the investigation of acquired disorders of peripheral nerves (Robinson, 2000) and as such it is difficult to understand why it does not have a clear role in the management of BPPN, a most severe example of peripheral nerve injury. The purpose of this review is to present an analysis of why this anomalous situation may have arisen and how the use of EMG might be improved.

There are two major concerns to the clinician presented with a BPPN. The first is the aetiology. This will be of particular interest to the obstetricians who will be keen to audit the results of their interventions with the aim of improving management. Unfortunately, in many countries in the world, this laudable aim in BPPN is eclipsed by legal advisers wishing to apportion blame and in so doing realise large settlements for their clients. This compounding factor should not divert attention from the important scientific investigation of the aetiology of BPPN and, for the purposes of this particular review, EMG's role.

The second major concern in BPPN is the accurate estimation of the prognosis. This is very difficult but has most important implications for the need and timing of corrective surgery. Much reliance is placed on the observation of recovery over time. If EMG cannot address these two fundamental questions its usefulness will undoubtedly be diminished. This review is going to focus on these two areas and consider how effective EMG is in answering the problems that BPPN pose.