The incidence of brachial plexus birth injuries has been largely stable over the last decade despite improvements in the safety of obstetric practice and training. Large cohort studies over the years have noted an incidence of 0.4–2.5/1000 live births, with little change over time despite changes in obstetric practice designed to reduce perinatal complications [6–9]. Some have proposed that this is the result of a concurrent rise in average birth weight [5].

A 2008 study of children in the United States utilized the Kid’s Inpatient Database to produce an incidence of 1.5/1000 births by identifying injuries in three separate years over the period from 1997 to 2003. There were no significant associations in ethnic or socioeconomic factors that could be ascertained. Furthermore, this observational cohort study was more optimistic about a decreasing rate of injury over time, from 1.7 to 1.3 per 1000 live births over the 6-year period [10].

We have seen that a number of fetal and maternal characteristics are associated with the presence of injuries of the neonatal brachial plexus. Maternal diabetes, fetal macrosomia, prolonged labor, forceps delivery, primiparity, increasing maternal age, and shoulder dystocia have all been identified as risk factors for injury. Of these, shoulder dystocia and fetal macrosomia have been singled out as the higher risk conditions. Twin gestation and Caesarian delivery have been associated with a lower rate of brachial plexus palsy [10]. Some centers have attempted the use of elective Caesarian section to reduce the incidence of brachial plexus injury in the setting of multiple prenatal risk factors. One group noted a decreased risk of brachial plexus injury and clavicular fracture with Caesarian section compared with vaginal delivery. However, the category “other birth trauma ” saw an increase in risk with Caesarian delivery [11]. A head-to-head study investigating elective Caesarian delivery demonstrated no significant decrease in the incidence of brachial plexus injury [9].

In the delivery room, identification of the injury is the first step. Localizing the nerve injury may require further study, as the evaluation of a newborn infant will be limited early on by pain. It should be noted, however, that the pain is typically not the result of the nerve injury itself [12] but rather the corresponding fractures and muscular trauma. Neonates affected by brachial plexus palsies have also frequently been noted to suffer from other injuries. Clavicular fractures, facial nerve palsies, cephalohematomas, and arm ecchymoses have all been notably associated with brachial plexus palsies and are the typical stigmata of a traumatic delivery [6, 9].

The most common presenting finding in the neonate is the classic Erb’s Palsy , which arises from a lesion of the C5–6 roots. The arm is internally rotated and abducted at the shoulder, the elbow extended, and the forearm is pronated with flexed wrist and fingers (Fig. 4.2). Injuries may involve C4, causing respiratory distress as a result of phrenic nerve disruption. With C7 involvement, the triceps may be impaired as well. In the most severe cases, the entire plexus may be involved, causing complete paralysis of the arm (Fig. 4.3).

More proximal injuries can sometimes be identified by findings related to loss of function of nerves branching early from cervical roots or in close association with the roots themselves. A Horner’s syndrome may occur due to sympathetic chain injury where it is adjacent to the roots of C8 and T1. Winged scapula deformities result from injuries to the C5–7 roots proximal to the takeoff of the long thoracic nerve. Babies with brachial plexus injury often preferentially turn their heads away from the affected side, resulting in torticollis and/or positional plagiocephaly [5]. Furthermore, patients with residual deficits have sometimes been noted to have differences in upper extremity length when compared to the non-injured side, potentially compounding the degree of disability [13].

Recovery rates have generally been reported as favorable. Early studies of recovery rates of children after injury identified flaccid paralysis, Horner’s syndrome, and diaphragmatic dysfunction as poor prognostic indicators, as well as the absence of shoulder dystocia at delivery [2]. Large prospectively collected cohorts from the 1980s reported high overall rates of recovery, ranging from 77.8 % to as high as 95.7 % [6, 7]. However, more recent discussions of the rate of spontaneous recovery have somewhat tempered the optimism of some practitioners. Earlier reports may have overstated the likelihood of improvement without intervention [10] and newer data suggest that 30 % or more of the infants injured will not achieve a satisfactory outcome without intervention [14, 15]. Injuries involving more roots—i.e., C5–7 rather than only C5–6—portend a worse prognosis. In a study of 168 infants with brachial plexus palsy between 1990 and 2005, it was noted that infants with C5–6 lesions recovered completely 86 % of the time [16]. Those with C5–7 lesions, however, recovered only 38 % of the time while those with lesions of the entire plexus did not recover fully. These observations, among others, have resulted in changes to practice patterns with respect to timing of surgical evaluation and intervention for brachial plexus birth injury.

Discussions of the natural history of brachial plexus birth injuries are inextricably linked to the consideration of surgical repair. Identifying infants who are destined for a poor functional outcome is critical, and is largely in the hands of the child’s primary healthcare providers. Defining a satisfactory outcome is critical to the consideration of recovery rates. This has led to the development of multiple rating scales and tools for evaluators to characterize injuries to the infant brachial plexus.

The simplest observations reported by studies of infant recovery after injuries to the brachial plexus have hinged on evaluations of upper arm strength. For example, it has been demonstrated that infants who recovered fully had reached greater-than-antigravity strength in the deltoid, biceps, and triceps muscles by the age of 4.5 months. All others had persistent varying degrees of weakness [14].

Most instances of BPBP are identified immediately following delivery and require several important initial steps. Care should be taken to avoid exacerbating injury or causing pain on the affected side, and plan X-rays of the upper extremity and shoulder should be completed to avoid missing associated fractures and dislocations. The infant should also be thoroughly examined to identify ptosis or miosis , which may herald the presence of a Horner’s syndrome [1]. The next steps include evaluation by pediatric physical and occupational therapists, as well as regular follow-up to identify signs of recovery and, conversely, the infants who do not recover and may warrant referral for surgical management.

Multiple classification systems have been proposed to characterize brachial plexus injury in attempts to standardize the evaluation and monitoring of clinical progress in these children. The most widely recognized of these was published by the British Medical Research Council (BMRC) in [17] and evaluates infants using limb positioning, establishing a grading system from 0 to 5 to describe a range of muscle strength. The challenges of grading resistance in infants were observed over time, and a modified BMRC scale was introduced to accommodate this. The adjustment limited the grades to M0 to M3, thus reducing the gradations used to measure different degrees of manual resistance in the infant. This scale has been used widely as an outcome score for motor recovery [18].

The Score of 10 is a scoring system that was introduced in 1997 in order to characterize children with persistent deficits after birth injuries. It is performed at an age at which the child can follow verbal prompts to complete a range of active movements and assigns greater weight to movements that are particularly important to function. The total comprises Erb and Klumpke scores, representing evaluations of the upper and lower plexus (Table 4.2). The authors proposed that high scores indicated children with good function, mid-range scores defined children who had some degree of impairment but sufficiently good function to benefit from surgery, and those with low scores would be unlikely to achieve sufficient benefit from intervention [19]. As this score can only reliably be applied to older children, it is not helpful in the early evaluation and referral of infants with injuries.