Brachial plexus palsy: an old problem revisited again. II. Cases in point

Maternal Endogenous Forces and Shoulder Dystocia

Childbirth is a complicated biomechanical process that many take for granted. However, the delivery forces generated by a mother (uterine contractions and maternal pushing) are strong and have a significant effect on the body and tissues of the fetus, especially during the second stage of labor. Although most infants are born without negative, force-related outcomes, in some infants the normal forces of labor cause an injury that can have either temporary or permanent sequelae. The biomechanical situation is further complicated when an infant's shoulder impacts the maternal pelvis, which provides increased resistance and creates added stresses within the neonatal body and tissues.

Perinatal brachial plexus palsy

BACKGROUND

Perinatal brachial plexus palsy (PBPP) is a flaccid paralysis of the arm at birth that affects different nerves of the brachial plexus supplied by C5 to T1 in 0.42 to 5.1 infants per 1000 live births.

OBJECTIVES

To identify antenatal factors associated with PBPP and possible preventive measures, and to review the natural history as compared with the outcome after primary or secondary surgical interventions.

METHODS

A literature search on randomized controlled trials, systematic reviews and meta-analyses on the prevention and treatment of PBPP was performed. EMBASE, Medline, CINAHL and the Cochrane Library were searched until June 2005. Key words for searches included 'brachial plexus', 'brachial plexus neuropathy', 'brachial plexus injury', 'birth injury' and 'paralysis, obstetric'.

RESULTS

There were no prospective studies on the cause or prevention of PBPP. Whereas birth trauma is said to be the most common cause, there is some evidence that PBPP may occur before delivery. Shoulder dystocia and PBPP are largely unpredictable, although associations of PBPP with shoulder dystocia, infants who are large for gestational age, maternal diabetes and instrumental delivery have been reported. The various forms of PBPP, clinical findings and diagnostic measures are described. Recent evidence suggests that the natural history of PBPP is not all favourable, and residual deficits are estimated at 20% to 30%, in contrast with the previous optimistic view of full recovery in greater than 90% of affected children. There were no randomized controlled trials on nonoperative management. There was no conclusive evidence that primary surgical exploration of the brachial plexus supercedes conservative management for improved outcome. However, results from nonrandomized studies indicated that children with severe injuries do better with surgical repair. Secondary surgical reconstructions were inferior to primary intervention, but could still improve arm function in children with serious impairments.

CONCLUSIONS

It is not possible to predict which infants are at risk for PBPP, and therefore amenable to preventive measures. Twenty-five per cent of affected infants will experience permanent impairment and injury. If recovery is incomplete by the end of the first month, referral to a multidisciplinary team is necessary. Further research into prediction, prevention and best mode of treatment needs to be done.

Newborn brachial plexus palsy

Understanding the causation of newborn brachial plexus injuries and why they are not decreasing in frequency.

Long-term neurologic outcome of infants born by cesarean section

Prevention of neurologic injury to the fetus through skilled and attentive care during the peripartum period is designed to identify signs of fetal distress so that appropriate obstetric interventions can occur. The impact of mode of delivery on neurologic outcome varies depending on the clinical indication for cesarean delivery and the associated maternal and fetal conditions. This review summarizes current knowledge of the impact of mode of delivery on long-term neurologic outcome.

Permanent brachial plexus injury following vaginal delivery without physician traction or shoulder dystocia

A vaginal delivery that resulted in a permanent brachial plexus injury unassociated with shoulder dystocia or physician traction is reported by the delivering physician. This case demonstrates unequivocally that not all permanent brachial plexus injury at vaginal birth is due to physician traction.

Part 2. Distinguishing physical characteristics and management of brachial plexus injuries

Brachial plexus injuries (BPI) are usually readily apparent at or shortly after birth. Failure of caregivers to recognize and appropriately treat BPI may contribute to the risk of life-long neuromuscular dysfunction for the infant and represents a serious medical-legal liability for the delivery provider. This article is the second in a series on BPI and provides a standard classification and a systematic guide to physical examination of the infant with suspected BPI. Conditions that mimic BPI are discussed along with diagnostic studies used to confirm this disorder. The natural history and predictors of outcome are presented along with a sample treatment protocol. Pictures and video clips are provided to enhance the reader's understanding of the consequences of this injury and the potential for improvement with surgical treatment. Useful Internet resources for parents, focused discharge planning, and guidelines for appropriate monitoring and follow-up are provided. Advantages of early referral and management by a multidisciplinary team at a brachial plexus specialty center are discussed.

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

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.

Management of infant brachial plexus injuries

Management of brachial plexus injuries is geared toward normalization of limb function, primarily through optimization of nerve regeneration and mechanical increase in elbow flexion and shoulder stabilization. Changes in the skeletal muscles and the osteous structures of the upper extremity are ongoing throughout the course of treatment, mandating continual assessment and aggressive rehabilitation. In patients who present too late for microsurgical intervention, irreversible changes take place in skeletal muscles, highlighting the importance of early referral. However, secondary procedures have been shown to be beneficial in older patients and in those whose primary procedures failed. Further advances in bionics and stem cell therapy may help replace the dynamic functional deficits of obstetric brachial plexus palsy.

Brachial plexopathies: classification, causes, and consequences

The brachial plexus, which is the most complex structure of the peripheral nervous system, supplies most of the upper extremity and shoulder. The high incidence of brachial plexopathies reflects its vulnerability to trauma and the tendency of disorders involving adjacent structures to affect it secondarily. The combination of anatomic, pathophysiologic, and neuromuscular knowledge with detailed clinical and ancillary study evaluations provides diagnostic and prognostic information that is important to clinical management. Since most brachial plexus disorders do not involve the entire brachial plexus but, rather, show a regional predilection, a regional approach to assessment of plexopathies is necessary.

The Surgical Treatment of Obstetric Brachial Plexus Palsy

Learning Objectives: After studying this article, the participant should be able to: 1. Understand the natural history of obstetric brachial plexus injury with an emphasis on clinicopathologic features. 2. Develop an awareness of the indications and timing for both nonsurgical and surgical treatment. 3. Acquire knowledge of the current methodologies involved in primary and secondary brachial plexus reconstruction.Obstetric brachial plexus palsy is a potentially devastating form of cervical nerve injury that occurs in 0.38 to 2.6 births per thousand. In this review, we discuss fundamental clinicopathology and delve into the indications and methods of both nonsurgical and surgical strategies. An analysis of the major techniques of reconstruction is placed within the context of historical trends and a contemporaneous survey of the literature. On this basis, and given our own 12-year experience (with 415 surgically treated patients), several general conclusions can be made: (1) Early surgical intervention (3 to 6 months) is essential to optimizing long-term outcome in patients who have not had return of function in critical muscle groups. At Texas Children’s Hospital, we have developed an efficient multidisciplinary approach to primary brachial plexus exploration and reconstruction by integrating the neurosurgical, physical medicine and rehabilitation, neurologic, and plastic surgical services. (2) Secondary residual deformities—most notably the quintessential internal rotation and adduction deformity of the upper extremity—arise from both prolonged conservative management and failed surgical treatment; however, an effective armamentarium of reconstructive options (tendon transfers, muscle releases, neurotizations, and free muscle flap transplantations) has evolved to markedly improve the functional status of these patients. (3) Innovative reconstructive approaches, including nerve grafting, intraplexal and extraplexal neurolysis, and nerve transfers, should be well planned and applied for maximal functional recovery of the extremity. Priorities for the restoration of hand function, elbow flexion, and shoulder abduction should be the goal.

Congenital brachial palsy: incidence, causes, and outcome in the United Kingdom and Republic of Ireland

OBJECTIVES

To determine the incidence and study the causes and outcome of congenital brachial palsy (CBP).

DESIGN

Active surveillance of newborn infants using the British Paediatric Surveillance Unit notification system and follow up study of outcome at 6 months of age.

SETTING

The United Kingdom and Republic of Ireland.

PARTICIPANTS

Newborn infants presenting with a flaccid paresis of the arm (usually one, rarely both) born between April 1998 and March 1999.

MAIN OUTCOME MEASURES

Extent of the lesion at birth and degree of recovery at 6 months of age.

FINDINGS

There were 323 confirmed cases giving an incidence of 0.42 per 1000 live births (1 in 2300). Significant associated risk factors in comparison with the normal population were shoulder dystocia (60% v 0.3%), high birth weight with 53% infants weighing more than the 90th centile, and assisted delivery (relative risk (RR) 3.4, 95% confidence interval (CI) 2.9 to 3.9, p = 0.0001). There was a considerably lower risk of CBP in infants delivered by caesarean section (RR 7, 95% CI 2 to 56, p = 0.002). At about 6 months of age, about half of the infants had recovered fully, but the remainder showed incomplete recovery including 2% with no recovery. The relative risk of partial or no recovery in infants with extensive lesions soon after birth compared with those with less extensive lesions was 11.28 (95% CI 2.38 to 63.66, p = 0.000005).

CONCLUSIONS

The incidence of CBP in the United Kingdom and Republic of Ireland is strikingly similar to that previously reported nearly 40 years ago. Most cases are due to trauma at delivery, which is not necessarily excessive or inappropriate. Given the uncertainty about the appropriate management of these infants, serious consideration should be given to a formal clinical trial of microsurgical nerve repair.

Erb's palsy contrasted with Klumpke's and total palsy: different mechanisms are involved

OBJECTIVE

The purpose of this study was to examine the available evidence regarding the nature of the forces that were involved in the production of a lower plexus palsy or a total (whole arm) palsy, as contrasted with the nature of the forces that resulted in an upper plexus palsy.

STUDY DESIGN

This was a review of studies that dealt with specific mechanisms that were supplemented by reports of total palsy that were gleaned from the literature and case reports from the clinical and medical legal cases of the authors.

RESULTS

Studies of the forces involved in brachial plexus injury in adults and from cadaver studies in infants who were stillborn or who died in the newborn period attest to the nature of the forces needed to damage the lower plexus. This evidence is reinforced by the case reports.

CONCLUSION

Forces other than simple widening of the head-shoulder angle are necessary to disrupt the roots or cords of the lower brachial plexus. The position of the arm and direction of the forces that are applied determine the nature of the lesion.

Obstetric lesions of the brachial plexus

The few studies on prognosis of obstetric lesions of the brachial plexus that are not hampered by selection bias or a short follow-up suggest that functional impairment persists in 20-25% of cases, more than commonly thought. Electromyography (EMG), potentially useful for prognosis, is often considered of little value. Denervation in the first week of life has been interpreted as evidence of an antenatal lesion, but is the logical result of the short axonal length affected. EMG performed at close to the time of possible intervention (3 months) usually shows a discrepancy: motor unit potentials are seen in clinically paralyzed muscles. This can be explained in five ways: an overly pessimistic clinical examination; overestimation of EMG recruitment due to small muscle fibers; persistent fetal innervation; developmental apraxia; or misdirection, in which axons reach inappropriate muscles. Further research into the pathophysiology of obstetric lesions of the brachial plexus is needed to improve prognostication.

Mathematic modeling of forces associated with shoulder dystocia: a comparison of endogenous and exogenous sources

OBJECTIVE

A mathematic model was developed to estimate the compressive pressure on the fetal neck overlying the roots of the brachial plexus by the symphysis pubis during a shoulder dystocia event. The induced pressure was calculated for both exogenous (clinician applied) and endogenous (maternal and uterine) forces during the second stage of labor.

STUDY DESIGN

Intrauterine pressure and clinician-applied force data were taken from the existing literature. A free-body diagram was generated and equilibrium equations were used to calculate the contact pressure between the base of the fetal neck and the symphysis pubis during a shoulder dystocia event.

RESULTS

Clinician-applied traction to the fetal head (exogenous force) led to an estimated contact pressure of 22.9 kPa between the fetal neck and the symphysis pubis. In contrast, uterine and maternal expulsive efforts (endogenous forces) resulted in contact pressures that ranged from 91.1 to 202.5 kPa. The estimated pressures resulting from endogenous forces are 4 to 9 times greater than the value calculated for clinician-applied forces.

CONCLUSION

Neonatal brachial plexus injury is not a priori explained by iatrogenically induced excessive traction. Spontaneous endogenous forces may contribute substantially to this type of neonatal trauma.

Obstetric brachial plexus injury: risk factors related to recovery

OBJECTIVE

To investigate if multivariate risk calculation can discriminate those infants who do not recover after an obstetric brachial plexus injury (OBPI).

STUDY DESIGN

All liveborn infants without lethal congenital abnormalities from 1988 through 1996 with a gestational age > or =30 weeks were included. Outcome variables were all OBPI and non-recovered OBPI. Risk calculation was performed by univariate analysis for all infants and by multivariate logistic analysis for all singleton infants delivered vaginally in cephalic presentation.

RESULTS

A total of 62 of 13 366 liveborn infants sustained an OBPI (0.46%). Seventeen (27%) did not recover completely. Birth weight, female sex, second stage >60 min, diabetes, multiparity, maternal age and non-Caucasian origin were important risk factors for non-recovered OBPI. A model without birth weight, which can not be measured accurately antepartum, is considerably less effective. Risk factors for all OBPI and for non-recovered OBPI were similar.

CONCLUSION

A predictive multivariate model is of limited value due to the low incidence of non-recovered OBPI. However, it may be useful to discriminate individual cases with exceptional risk.

Perinatal brachial plexus palsy

Perinatal brachial plexus palsy (PBPP) has been traditionally classified into three types: upper plexus palsy (Erb's) affecting the C5, C6, and +/- C7 nerve roots, lower plexus palsy (Klumpke's) affecting the C8 and T1 nerve roots, and total plexus palsy. Although most cases will resolve spontaneously, the natural history of the remaining cases is influenced by contractures of uninvolved muscle groups and subluxation or dislocation of the shoulder and elbow. Microsurgical nerve repair has demonstrated to provide improved outcomes compared to conservative treatment, while advancements in secondary reconstruction have offered significant improvements in the performance of activities of daily living for older children with unresolved plexus palsy.

Brachial plexus palsy: an in utero injury?

Acquired brachial plexus injury historically has been linked with excessive lateral traction applied to the fetal head, usually in association with shoulder dystocia. Recent reports in the obstetric literature, however, have suggested that in utero forces may underlie a significant portion of these injuries. Brachial plexus palsies may therefore precede the delivery itself and may occur independent of the actions of the accoucheur. Thus we propose that the long-held notions of a traction-mediated pathophysiologic mechanism for all brachial plexus injuries warrant critical reappraisal.

Shoulder dystocia

Shoulder dystocia continues to represent a largely unpredictable and potentially disastrous obstetric emergency. Recent attention has been focused on the effectiveness of obstetric maneuvers employed to alleviate shoulder dystocia. Reports have also questioned the traditional thinking that brachial plexus injury is caused by application of excessive lateral traction to the fetal head. Rather, in-utero forces may underlie a significant portion of these injuries.