Pediatrics

Birth injuries: peripheral nerves

OVERVIEW: What every practitioner needs to know

Are you sure your patient has a congenital brachial plexus palsy? What are the typical findings for this disease?

Most common symptoms:

Otherwise healthy newborn has one arm that is limp and does not demonstrate active movement (may or may not have hand movement).

The Moro reflex will be asymmetrical, and no reflexes can be obtained in the affected arm.

In an older infant the arm is frequently held in internal rotation at the shoulder, with the forearm pronated with the palm down or it may hang limp at the child's side.

Decreased musculature may or may not be noticeable in the affected arm compared with the other side.

Associated Injuries (may occur in conjunction with congenital brachial plexus palsy but are not causitive of congenital brachial plexus palsy)

  • Fractured clavicle

  • Fractured humerus

  • Torticollis

  • Cephalohematoma

  • Facial nerve palsy

  • Horner syndrome

  • Diaphragmatic paralysis

  • Spinal cord injury

Clinical findings in older children with history of congenital brachial plexus palsy

The root levels (C5-8,T1) affected, as well as the timing and degree of neurologic recovery, affect the outcome and as such the clinical picture in an older patient.

In upper trunk (C5-6) lesions, there may be persistent difficulty with active shoulder external rotation, abduction, forward flexion, symmetrical elbow flexion, and forearm supination. This results in the classic Erb palsy with a "waiter's tip" posture.

In entire plexus lesions, the entire arm and hand frequently have persistent weakness and the child may demonstrate a degree of neglect toward the limb.

In pure lower trunk lesions (C8-T1), which are very rare, the child will demonstrate a paralyzed hand with good shoulder and elbow strength and movement. This is known as a Klumpke palsy.

In Erb palsy, children may demonstrate a "trumpet sign" (shoulder abduction to 90 degrees to assist ease of elbow flexion) when asked to bring the hand to the mouth.

The affected limb is often smaller (shorter in length and smaller in circumference) with atrophied musculature in children who have had incomplete neurologic recovery.

A Putti sign may be seen where the medial edge of the scapula can be seen protruding above the shoulder line when the child abducts the shoulder.

Over time, imbalance between the less affected (thus stronger) shoulder internal rotator muscles and the more affected and weaker external rotators can result in the development of internal rotation contracture and glenohumeral deformity. This leads to mechanical restrictions in active and passive shoulder range of movement and posterior subluxation of the humeral head.

Sensory abnormalities may increase the frequency of self-injurious behavior toward the affected limb, such as biting or picking of the fingernails and skin to the point of tissue damage. This is more prevalent in children with total plexus involvement.

Children are at increased risk for scoliosis because of muscle imbalance and asymmetrical movement patterns.

Prognostic indicators

Severity of injury depends not only on how many nerves are affected but also on the severity of damage to the nerves:

It is important from a prognostic and management standpoint to try and differentiate between avulsion injuries (nerve root completely pulled out from the cord) and other varying degrees of nerve injury.

There are three basic types of nerve injury:

Neuropraxic lesions occur when the nerve is stretched, resulting in local myelin injury, but the underlying axons remain intact. Recovery depends on the percentage of myelin affected and occurs over a period of weeks to months

Axonotmesis-type lesions or nerve rupture lesions range in their severity depending on the degree of axonal elements that are disrupted. Wallerian degeneration of the nerves occurs, but if sufficient endoneurium and perineurium remain intact, this will provide a structure for the regenerating axons to follow and improves prognosis. However, if there is disruption of the endoneurium, the regenerating axons may regrow in a "tangle," resulting in a neuroma, and the regenerating nerve will not achieve congruity. This results in a poor prognosis and requires surgical excision and potential grafting.

Neurotmesis or avulsion-type lesions result in complete nerve severance. This is the worst prognosis because the roots have typically been completely torn from the spinal cord in this scenerio. Surgery is necessary to gain any meaningful recovery.

Referral to an experienced clinician or brachial plexus multidisciplinary clinic or center for close follow-up and managment is important if complete neurologic recovery does not occur within the first 3 weeks of life.

Classifying severity of injury

Narakas classification

Class 1: Classic Erb Palsy (affecting C5-6 nerve roots—infant lacks ability to abduct shoulder or externally rotate shoulder, flex elbow, or supinate forearm; wrist and hand movments are intact.

Class 2: C5-7 roots are affected—the addition of C7 causes additional weakness in wrist extension and digital extension; flexion remains intact

Class 3: All roots (C5-8 and T1) are affected and the infant has a flail arm with no active movement noted in the hand or wrist; no other concurrent nerve injuries are noted.

Class 4: Most severe—all roots are affected but the infant also has concurrent Horner syndrome evident (ptosis, miosis, anhidrosis) and should be evaluated closely because a concurrent phrenic nerve injury with a weakened (noted as elevated on roentgenogram) hemidiaphram may also be present.

Classes 3 and 4: Typically associated with worse prognosis and limited spontaneous neurologic recovery—these injuries more frequently include root avulsions and severe nerve rupture injuries; presence of Horner syndrome with or without phrenic nerve injury is especially associated with avulsion-type injuries because the sympathetic ganglion is located in relatively close proximity to the cord.

What other disease/condition shares some of these symptoms?

Other conditions that may mimic congenital brachial plexus palsies:

Spinal cord injury: suspect this if the child has bilateral involvement and evidence of leg weakness as well. Male infants may have priapism in the acute period.

Brain injury (stroke, malformation, or mass): suspect if the child has hemiparesis—leg involvement as well as arm involvement. Reflexes may be brisk as opposed to absent. Hemiparesis may have a variable degree of arm versus leg involvement (one or the other may be more involved) but asymmetry in tone in a newborn's examination side to side should lead to more close observation and consideration of brain imaging.

Amyoplasia congenita: congenital absence of muscles in the arm

Congenital varicella: typically complete plexus involvement, frequently bilateral involvement with other associated findings such as scarring/ hypertrophy of the skin, and hypoplasia of one or more limbs or digits. The anterior horn motor neurons and dorsal root ganglia typically are both affected.

Mass: tumor or hemangioma compromising the vasculature or directly compressing or even infiltrating the plexus

Infection: osteomyelitis of the vertebral body or transverse process or of the clavicle or humerus may result in inflammation and vascular compromise of the brachial plexus.

What caused this disease to develop at this time?

Traction of the nerves that contribute to the brachial plexus, located between the neck and the shoulder/axilla causes brachial plexus birth palsies.

Perinatal risk factors include:

  • Macrosomia (large for gestational age), birth weight greater than 4 kg

  • Maternal type 1 or type 2 diabetes or gestational diabetes

  • Family history or history of mother previously delivering a neonate with brachial plexus palsy

  • Prolonged labor

  • Breech delivery with difficult arm or head extraction

  • Delivery requiring vacuum or foreceps assistance

  • Difficult delivery (delivery by cesarean section may reduce risk but does not eliminate possibility of brachial plexus injury)

  • Shoulder dystocia

  • Fetal distress or other causes of muscle hypotonia in the infant may result in less protection of the plexus during the delivery process

What laboratory studies should you request to help confirm the diagnosis? How should you interpret the results?

Electrodiagnostic studies (nerve conduction studies and electromyography) may be helpful in determining the severity of the lesion. The presence of normal sensory nerve conduction in the absence of motor nerve conduction is diagnostic of a root avulsion. Denervation potentials can be seen on needle examination by 2-3 weeks after injury and may assist in determining timing of the injury.

Caveats:

These are technically difficult studies to perform in young children. Electromyography may underestimate the severity of the injury, providing false optimism. Most experienced clinicians at brachial plexus centers and brachial plexus microsurgeons rely on serial physical examinations to assess neurologic recovery.

Helpful imaging studies

Radiography can be used to look for clavicle or humerus fracture/dislocation or hemidiaphram paralysis.

Magnetic resonance imaging (MRI) is very helpful in detecting root avulsions. MR myelography and neurography may improve diagnostics. MRI has a clear advantage over the previous gold standard of computed tomography (CT) myelography because it does not result in any radiation exposure and is noninvasive.

CT myelography is equally sensitive in detecting root avulsions but is invasive (requiring contrast administration) and is associated with significant radiation exposure. Both MRI and CT myelography require sedation/general anesthesia of the infant to obtain adequate images.

Older children with a history of brachial plexus injuries and partial recovery may require imaging evaluation of the shoulders (typically MRI), as muscle imbalances frequently lead to glenohumeral deformity and may require surgical management.

Confirming the diagnosis

All patients with a brachial plexus palsy identified at birth should be referred to a physical or occupational therapist in the nursery for family education. If the child has not had complete recovery by 3-4 weeks he/she should be referred to a specialty brachial plexus clinic or center.

If a high concern exists for an avulsion injury or if the bicep has not achieved antigravity strength by 3 months of age, the child should be referred to a brachial plexus microsurgical specialist for consideration of primary surgery such as, for example, nerve decompression or neuroma resection. Timing of primary neurologic surgery typically occurs between 3 and 9 months of age, sooner (closer to 3 months) for avulsion injuries.

For persistent contractures and glenohumeral bony deformity, orthopedic surgery referral is indicated.

If you are able to confirm that the patient has a congenital brachial plexus palsy, what treatment should be initiated?

Immediate treatments include the following:

Therapy referral in the nursery for parent and caregiver instruction in careful handling of the infant to avoid additional traction on the injured limb or neck to protect the nerves in the first week of life. Immobilization of the arm by pinning with clothing across the chest is controversial and, instead, instruction on and institution of gentle range of motion exercises is preferred.

Outpatient physical or occupational therapy should then be instituted (Ideally a therapist specially trained and experienced in pediatrics and specifically congenital brachial plexus injuries, such as a pediatric hand therapist, should be sought).

Goals of therapy are to promote and maintain shoulder, elbow, hand, and wrist range of motion; improve sensory input to affected limb; strengthen weak muscles; and promote function and attainment of developmental milestones. Parents need to be educated by the therapists as well to carry over stretching and facilitation techniques into the home on a daily basis.

If a severe injury such as a root avulsion or rupture is suspected clinically, referral to a brachial plexus microsurgery specialist is warranted to further evaluation and consideration for primary neurosurgical procedures as stated above.

Longer term treatments include the following:

Continued therapy to encourage bimanual activities, improve sensory input, and promote function and also to maintain joint range of motion with stretching, strengthening, and myofascial release techniques to minimize or prevent as best as possible contracture development and glenohumeral bony deformity.

Splinting may be necessary to maintain anatomic alignment in the wrist or hand or may be necessary to maintain shoulder range of motion (shoulder/elbow/wrist/ hand orthosis [so-called Statue of Liberty splint]) when loss of shoulder external range of motion is noted as the child grows.

Electrical stimulation may be a technique used by therapists to work on strengthening weak muscles in the shoulder and arm.

If progressive loss of range of shoulder motion occurs and cannot be corrected with aggressive stretching, myofacial release, and splinting techniques with the therapist, referral to a specialist should be made to better evaluate the glenohumeral joint and consider botox injections to improve shoulder range of motion or to consider surgical intervention to balance forces and improve joint biomechanics.

Surgical options include tendon transfers, contracture releases, and bony osteotomies.

What are the adverse effects associated with treatment option?

With aggressive forearm supination, children with congenital brachial plexus palsy are susceptible to radial head dislocations, which are unlike "nursemaid’s elbow" in that they are somewhat difficult to reduce and may lead to permanent contracture and deformity.

Without therapy, children are at high risk for agnosia of the affected limb, severe muscle contractures, severe glenohumeral deformity, and posterior shoulder dislocation. Even aggressive therapy may not completely mitigate these risks; however ideally such therapy will be able to postpone and lessen the extent of any orthopedic surgical intervention.

Outcomes Associated with Congenital Brachial Plexus Palsy

Natural history studies suggest that “good” (i.e., the affected arm regains some useful function) recovery occurs in 75%-95% of cases. Recovery typically is better in upper trunk lesions than in lower trunk lesions. Entire plexus involvement (Narakas classes 3 and 4) is a negative prognostic indicator, as is presence of Horner syndrome and phrenic nerve involvement.

Full recovery by 3-4 weeks of age carries the best prognosis, as contractures or glenohumeral deformities do not typically develop in these children.

Recovery of antigravity biceps function by 4 weeks of age typically portends eventual complete neurologic recovery. Infants should still be monitored for shoulder contractures and glenohumeral abnormalities.

Delayed complete neurologic recovery (typically occurring between 1 and 4 months of age) carries a good functional prognosis but is associated with a high incidence of joint contractures and glenohumeral deformities. A clinical marker for this group is demonstration of at least antigravity deltoid and bicep function by the third month of life.

Recovery of antigravity biceps function after 4 months generally indicates an incomplete neurologic recovery and a worse functional prognosis. These children are at high risk of development of joint contractures and glenohumeral deformity. If a patient has not recovered antigravity biceps function by 6 months of age, they will never achieve complete neurologic recovery and will have persistent weakness along with increased risk for glenohumeral deformity.

Early exposure to imbalanced muscle forces around the shoulder results in glenohumeral joint deformities, contracture development, and increased predisposition to posterior shoulder dislocation.

Epidemiology of Congenital Brachial Plexus Palsy

The incidence of congenital brachial plexus palsies has been quoted as being anywhere between 0.13 and 3.6/1000 live births; however recent studies quote that it is closer to approximately 0.38-1.56/1000 live births (1/1000).

The incidence of permanent impairment is between 3% and 25%. There is no link between sex or race in incidence of congenital brachial plexus palsies.

There is a slight increased incidence of right arm involvement (51% of cases versus 45% in the left arm). There is a 4% incidence of bilateral involvement.

How can congenital brachial plexus palsies be prevented?

Good prenatal care may identify risk factors for brachial plexus palsies. Cesarean section lowers the incidence of shoulder dystocia in large for gestational age infants greater than 5 kg, which is otherwise 20% in this group. Shoulder dystocia and large for gestational age are risk factors for congenital brachial plexus palsies.

What is the evidence?

Alfonso, D. "Causes of neonatal brachial plexus palsy". Bull NYU Hosp Joint Dis. vol. 69. 2011. pp. 11-6.

(This is a nice article discussing the proposed pathophysiology and physics involved in congenital brachial plexus palsy as well as other potential causes of plexus injuries at birth. The article stresses that traction forces alone cannot account for all incidents of congenital brachial plexus palsies and urges clinicians to abandon the term obstretrical brachial plexus palsy.)

Gilbert, A, Tassin, JL. "Surgical repair of the brachial plexus in obstetric paralysis". Chirurgie. vol. 110. 1984. pp. 70-5.

(Although this original article is in French, it is one of the earliest articles describing primary neurosurgical techniques and outcomes after these procedures. It is frequently cited and has produced many subsequent studies on natural history versus neurosurgical repair.

Hale, H, Bae, DS, Waters, PM. "Current concepts in the management of brachial plexus birth palsy". J Hand Surg Am. vol. 35. 2010. pp. 322-31.

(This article summarizes and reviews current literature regarding natural history and timing of interventions and discusses current best evidence for microsurgery neurosurgical repairs and secondary orthopedic procedures.)

Orestes, M. "Brachial plexus palsy after cesarean delivery: an intrauterine phenomenon?". Obstet Gynecol. vol. 107. 2006. pp. 35S.

(This article discusses the rare cases of congenital brachial plexus palsy noted after cesarean section or uneventful vaginal deliveries with no documented shoulder dystocia or other identified traction forces.)

Piatt, J. "Birth injuries of the brachial plexus". Pediatr Clin North Am. vol. 51. 2004. pp. 421-40.

(Another nice summary article discussing the natural history, management recommendations, and timing of interventions in congenital brachial plexus palsy.)

Smith, NC, Rowan, P, Benson, LJ. "Neonatal brachial plexus palsy. Outcome of absent biceps function at three months of age". J Bone Joint Surg Am. vol. 86. 2004. pp. 2163-70.

(A longitudinal prospective study that looked at the timing and relation of bicep function to long-term outcome to try and make recommendations regarding neurosurgical repair.)

Semel-Concepcion, J, Gray, JM, Nasr, H. "Neonatal brachial plexus palsies".

(This is a nice and easily accessible overview of the background, etiology, treatment recommendations, and options that is fairly comprehensive inscope.)

Waters, P. "Comparison of the natural history, the outcome of microsurgical repair, and the outcome of operative reconstruction in brachial plexus birth palsy". J Bone Joint Surg. vol. 81. 1999. pp. 649-59.

(Excellent article discussing prognostic factors and outcomes in congenital brachial plexus palsies. Attempts to better clarify recommendations for timing of interventions based on natural history findings.)

Waters, PM, Bae, DS. "Effect of tendon transfers and extra-articular soft-tissue balancing on glenohumeral development in brachial plexus birth palsy". J Bone JointSurg. vol. 87A. 2005. pp. 320-5.

(Article describes the glenohumeral deformities commonly seen over time in patients with brachial plexus birth palsies as well as reviews the common orthopedic techniques and procedures currently practiced to correct these deformities and improve shoulder function.)

Ongoing controversies regarding etiology, diagnosis, treatment

Timing of microsurgical repair in cases not involving root avulsionis still somewhat controversial. Recent studies suggest that microsurgical repair may improve outcome if there is no evidence of biceps recovery by 4-5 months of age.

There are several different surgical approaches to balance forces and optimize shoulder function in patients with glenohumeral deformity and contracture. It is important that the patients'families research and discuss these options carefully with their surgeons to be sure they have realistic postsurgery expectations.

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