History
When an infant is born with a brachial plexus palsy, the condition generally is apparent from birth. In a common scenario, the baby weighs over 4 kilograms and is the product of a difficult delivery to a multiparous woman, requiring the use of vacuum extraction or forceps. Upon delivery, which may involve anterior shoulder dystocia, the arm hangs loosely at the child's side. Respiratory depression may indicate an associated phrenic nerve palsy. [9]
Physical
Newborn findings
The infant with complete brachial plexus palsy (BPP; C5-T1) typically lies in the nursery with the arm held limply at his/her side. Deep tendon reflexes (DTRs) in the affected arm are absent, and the Moro response is asymmetrical, with no active abduction of the ipsilateral arm.
In children with total arm involvement, careful examination of the child's eye often demonstrates Horner syndrome (ie, miosis, ptosis, anhidrosis), suggesting injury to the stellate ganglion. [3]
Children with intrinsic hand weakness associated with BPP generally have Horner syndrome, and vice versa.
Respiratory status should be evaluated, since the phrenic nerve can be injured simultaneously.
The infant with an upper plexus palsy (C5-C7) keeps the arm adducted and internally rotated, with the elbow extended, the forearm pronated, the wrist flexed, and the hand in a fist. In the first hours of life, the hand also may appear flaccid, but strength returns over days to months.
The right side is injured in 51% of cases. Left BPP occurs in 45% of patients and bilateral injuries, in 4%.
The infant with a nerve injury to the lower plexus (C8-T1) holds the arm supinated, with the elbow bent and the wrist extended.
Sensation should be assessed closely, with the clinician noting any sensory loss in corresponding dermatomes.
Reflexes, typically absent in the affected limb, should be evaluated. This examination is particularly important in distinguishing BPP from hemiparesis, where reflexes may be brisk. Reflexes do not typically return in BPP except in the mildest injuries.
In the newborn nursery, it is essential that the physician carefully inspect the size of the hand and arm and the bulk of the pectoralis major muscle, along with palmar dermatoglyphics and limb range of motion (ROM), looking for clues indicating when the injury occurred. On occasion, injuries occur during gestation. In these cases, a child may, at the time of delivery, already have a smaller limb with asymmetrical palmar creases, pectoralis muscle atrophy, and/or joint contractures.
Associated injuries
The pediatrician must perform a careful examination of the infant with a BPP to look for associated injuries.
The most common associated (not causative) injuries include the following:
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Clavicular and humeral fractures
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Torticollis
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Cephalohematoma
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Facial nerve palsy
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Diaphragmatic paralysis
Findings in older children
The root level(s) and severity of injury ultimately determine the clinical picture and, in part, the outcome as a child ages.
The older child with BPP involving the upper trunk typically has difficulty with active shoulder abduction, forward flexion, symmetrical elbow flexion, and forearm supination.
With shoulder abduction, the medial edge of the scapula often can be seen protruding above the shoulder line, a manifestation referred to as Putti sign.
The reduction in shoulder abduction is due in part to weakness of the deltoid and in part to the lack of external rotation, which is needed for the greater trochanter to slide past the coracoacromial arch.
The term "trumpet sign" describes the child's typical pattern of bringing objects to the mouth (ie, shoulder abduction accompanied by elbow flexion).
Posterior subluxation of the humeral head can develop as the internal rotators of the shoulder overpower the weaker external rotators and become contracted.
Mild shortening and atrophy of the limb are observed.
Biting of the fingernails and hands to the point of tissue damage is not infrequent (4.7%) in children with BPP and is more prevalent in children with total BPP.
The child should be reevaluated on a regular basis to ensure that scoliosis does not develop from muscle imbalance and asymmetrical motor patterns.
Causes
For many years, blame has been placed on the obstetrician when a neonate has been diagnosed with brachial plexus palsy (BPP). The assumption has been that the method of delivery and the traction applied to the head and neck during the birthing process cause the injury as the shoulder crosses the pubic arch. This theory has been supported by the fact that less than 1% of all BPP cases have been found in cesarean section deliveries.
A retrospective study by Jennett and colleagues [10] (reiterated by Allen and coworkers [11] ) questioned this assumption and noted that there are 2 separate populations of children with BPP: those with shoulder dystocia and those without it. Jennett found that 22 of the 39 children with BPP who were studied did not have documented shoulder dystocia. Rather than having the traditional risk factors listed above, these infants had an average birth weight of 2.5-3.5 kg, and most were born to young, nulliparous women.
Gherman and colleagues proposed that the brachial plexus in many cases has been stretched in utero or in the descent of the fetus and may not represent a traction injury associated with the final stages of delivery. [12] They reviewed birth records of 9071 children delivered vaginally to determine the extent of association between shoulder dystocia and BPP. A total of 40 cases of BPP were noted (17 cases without shoulder dystocia and 23 cases with associated shoulder dystocia).
When shoulder dystocia occurred, the risk of BPP was 18.3-32%. According to Gherman, the characteristics of the injury in children with BPP were different in the presence and absence of shoulder dystocia. When dystocia was present, the affected shoulder usually was anterior (81%), but in children with BPP and no shoulder dystocia, the injured shoulder often was posterior (68%). Children who did not have shoulder dystocia but who sustained BPP tended to be slightly smaller than were unaffected children, exhibited an associated clavicular fracture, and were subject to a less favorable outcome.
In 2002, the American College of Obstetricians and Gynecologists recommended cesarean delivery for fetuses with an estimated weight of 5 kg or more, to reduce the prevalence of shoulder dystocia. If practitioners were to follow the recommendation, the affect on the cesarean delivery rate would be negligible, but the shoulder dystocia rate, which in this category of births is 20%, would be reduced.
In 2003, Raio and coworkers identified an increased incidence of brachial plexus injury among fetuses weighting more than 5 kg (2.86% vs 0.85% in fetuses weighing 4.5-4.599 kg), especially fetuses that developed shoulder dystocia. [13] The authors suggested that when the estimated birth weight exceeded 4.5 kg, women should be informed of the increased risk of perinatal morbidity (including brachial plexus palsy) prior to making a decision on the mode of delivery.
Most neonatal BPP occurs in the birthing process. [14] Risk factors for this type of injury, also referred to as obstetrical BPP (OBPP), include the following:
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Large birth weight (average vertex BPP, 3.8-5.0 kg; average breech BPP, 1.8-3.7 kg; average unaffected, 2.8-4.5 kg)
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Breech presentation
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Maternal diabetes
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Multiparity
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Second stage of labor that lasts more than 60 minutes
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Assisted delivery (eg, use of mid/low forceps, vacuum extraction)
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Forceful downward traction on the head during delivery [15]
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Previous child with OBPP
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Intrauterine torticollis
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Shoulder dystocia
The aforementioned study by Weizsaeker and colleagues compared pregnancies and deliveries involving 45 infants with Erb palsy with 90 controls. [7] The risk for the condition was higher for children whose mother had gestational diabetes. Mothers who did not have gestational diabetes but who nonetheless gave birth to children with Erb palsy were found to have higher blood glucose values after a 50 g glucose challenge. Other variables found to be independently predictive of Erb palsy were a long deceleration phase of labor, a long second stage, high birth weight, and high neonatal or maternal body mass. Being a member of the black population also was found to be independently predictive.
Other, less common causes of neonatal BPP include the following:
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Neoplasm (eg, neuromas, rhabdoid tumors)
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Intrauterine compression
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Humeral osteomyelitis
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Hemangioma
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Exostosis of the first rib
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Brachial Plexus. Image courtesy of Michael Brown, MD.
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Mallet classification.
