Introduction

The anatomy, incidence, etiology, demographics, and initial management of a child with brachial plexus palsy have been discussed in this chapter. Timely referral to a brachial center is recommended to allow for obtaining accurate baseline data, to perform serial examinations, and to determine the necessity of surgical intervention. These visits also allow time for the family to understand their child’s injury, ask appropriate questions, develop a rapport with the brachial plexus team, and gain confidence in the decision-making process.

The family must be comfortable with the brachial plexus team, as many of these surgeries are lengthy, tedious, difficult, and not without complications. In addition, secondary procedures may be necessary, and long-term follow-up is required. This chapter will discuss the initial referral of the child and the subsequent decision-making process regarding primary nerve surgery. The indications, timing, techniques, and rehabilitation of nerve surgery will be discussed.

Initial Referral

Upon referral, the initial evaluation reviews the birth history including prenatal, birth, and postnatal phases. The prenatal period focuses on the mom’s health with respect to gestational diabetes and weight gain. The number of previous pregnancies and birth histories are required information. Principal risk factors for shoulder dystocia are fetal macrosomia, gestational diabetes, and history of previous shoulder dystocia. The birth period focuses on the delivery with specific questions concerning the use of instruments (forceps or vacuum), the difficulty of the delivery, and any maneuver necessary to effect delivery. Parents are often unfamiliar with the term shoulder dystocia. We ask if their child was “stuck,” that infer dystocia. In addition, the maneuvers performed are unfamiliar terms. We ask were your legs bent to your chest (McRobert’s maneuver), did someone push of your belly (suprapubic pressure), and was the bay rotated during the delivery (Corkscrew or Rubin’s maneuver). The postnatal period focuses on the child’s health including APGAR scores, birth weight, need for resuscitation, necessity of intubation, results of X-rays, and requirement of neonatal intensive care admission. The initial movement in the affected arm is critical historical information as most parents simple state that their child “could not move their arm.” The presence or absence of shoulder, elbow, wrist, and hand (finger opening or closing) movement requires delineation. The goal of the postnatal questioning is to determine the extent of the initial brachial plexus injury and any interim improvement to date. In our clinic, the therapists play an integral role in the examination process and family education. They also guide and oversea any postoperative therapy.

The physical examination of the infant focuses on active and passive movement. Passive motion should be full and painless unless some muscle tightness has occurred following birth. The stretching of tight muscles will yield pain; however, passive motion is necessary to maintain supple joints. Painful passive motion not attributed to muscle tightness warrants further evaluation. X-rays may reveal an undetected fracture of the clavicle, humerus, or elbow. Active motion measurements require patience and experience. Infants are most comfortable resting on the laps of their parents versus stranded on an examination table. The mom or dad can rotate and position the child to allow examination of both limbs and to permit the assessment of gravity eliminated and against gravity movement. Infants respond to tactile stimulation and noise. Stroking the limb will induce movement as will sound, such as a rattle. Patience is truly a virtue during the examination. An uncooperative infant may be tired, poopy, or just irritable. A poopy child is better evaluated after a diaper change. A hungry infant may require feeding before examination; however, a completely satiated child will be somnolent.

The passive examination determines the suppleness of the joints while the active evaluation ascertains the presence or absence of nerve innervation and muscle activation. Passive motion is simply documented in degrees using a goniometer. In infants, the goniometer can be a protractor or a visual estimate (“ocular goniometer”) depending upon the child’s cooperation. Active motion utilizes the practical anatomy of the brachial plexus to determine the injury pattern and root involvement ( Table 12.1 ).

Active motion is graded according to the Active Movement Scale (AMS) developed at the Hospital for Sick Children in Toronto, Canada ( Table 12.2 ). A key grading rule during the scoring of the AMS is that a motion cannot be graded as 5 or higher unless the movement is full against gravity (grade 4). For example, elbow flexion must be full with against gravity before achieving a grade of 5, 6, or 7. We have applied a similar concept to our grading during manual muscle testing in older children. In other words, a patient must achieve full motion against gravity (grade 3) before being granted a grade 4 or 5. The AMS is an invaluable tool to assess infants before and after surgery. The AMS been shown to be a reliable measurement between observers.

Sensibility cannot be assessed in an infant. Clinical clues are finger moistness and withdraw from a gentle pinch. Pruning in the tub is another indication of intact nerve supply.

Classification

The classic disease severity measure is the Narakas classification that divides brachial plexus birth palsies into four groups. Group 1 is the classic Erb-Duchenne palsy (C5 and C6) injury. Group 2 is the extended Erb-Duchenne (C5, C6, and C7) injury. Groups 3 and 4 are total plexus palsies separated by the absence (group 3) or presence of Horner syndrome (group 4). The very presence of Horner syndrome (drooped eyelid, constricted pupil, sunken globe, and sweating deficiency along the affected side of the face), usually implies an avulsion injury at C8 and T1 ( Fig. 12.1 ). Horner syndrome has been shown to have independent unfavorable prognostic value. These Narakas groupings have been shown to have prognostic power, with dramatically lower full chances of recovery rates for Narakas 3 and 4 patients.

Residual left-sided Horner syndrome with ptosis (drooped eyelid) and miosis (constricted pupil). In addition, Horner’s syndrome can lead to different eye colors (heterochromia).

Courtesy of Shriners Hospital for Children, Philadelphia.

Nerve Injury

Brachial plexus birth palsy injuries are the result of traction across the brachial plexus. The traction induces strain (change in length) across the nerve roots and trunks. The amount of ultimate strain has several components that affect the degree of nerve damage including the magnitude of the force and the vector along the nerve. The injury represents a continuum with progressive injury to the nerve. Mild stretch disrupts the myelin sheath and interrupts nerve conduction without loss of continuity of the axon (neurapraxia). Recovery takes place via remyelination without Wallerian degeneration. Ongoing stretch exceeds the elastic limit of the nerve, damages the myelin sheath, and the underlying axons with loss of axon continuity (axonotmesis). The connective tissue of the nerve is preserved (epineurium, perineurium, and endoneurium). The entire nerve distal to the injury undergoes Wallerian degeneration that usually begins within 24–36 hours after injury and is complete 1–4 weeks later. The axonal degeneration is followed by degradation of the myelin sheath and infiltration by macrophages. The debris within the distal stump is removed to allow for regeneration. The motor and sensory cell bodies transition from their normal role as signaling center to a nerve cell growth-promoting center with upregulation and a surge in cellular activity. The cell body synthesizes the structural proteins essential for axonal repair and regeneration. Axonal sprouts emerge just proximal to the injury (first node of Ranvier) and project into the distal nerve stump. Many axon collateral sprouts enter the distal stump with expectations of regeneration. Those sprouts that land into incorrect target contact are pruned. Eventually, accurate motor neurons project their axons into muscle and accurate sensory neurons reach their sensory receptors. Axonal regeneration occurs at a rate of 1–3 mm per day. The extent of recovery is related to the response of the axonal sprouting and the distance to the motor end plate. Longer distances prognosticate lesser recovery as the motor end plates within the muscle undergo irreversible end plate demise between 18 and 24 months. Subsequent to this demise, additional nerve regeneration will be ineffective in reinnervating the muscle.

Continual stretch leads to complete disruption of the nerve including the sheath, axon, and encapsulating connective tissue (epineurium, perineurium, and endoneurium). This injury is called as a neurotmesis and results in irreversible intraneural scarring. The prognosis for recovery is bleak without surgical reconstruction. The intervening scar forms a neuroma that must be resected to allow for nerve reconstruction to allow regeneration across the defect. Another surgical option is nerve transfers distal to the injury that bypass the injury completely.

Neurapraxia is an entity separate and distinct from the more severe injuries of axonotmesis and neurotmesis. Traction axonotmesis and neurotmesis lesions, however, are a continuum with an overlap similar to a Venn diagram ( Fig. 12.2 ). Brachial plexus injuries often have features of neurapraxia, axonotmesis and neurotmesis and even within the same trunk different degrees of nerve injuries can coexist. This combination complicates terminology and the decision-making process for surgery.

Neurapraxia is a separate entity, but traction axonometesis and neurotmesis can overlap.

Brachial plexus birth injuries are supraclavicular (above the clavicle), although the injury can extend below infraclavicular. Axonotmesis typically occurs at the level of the trunk. Neurotmesis injury can occur at the level of the trunk (a.k.a. rupture). Neurotmesis can also occur when the nerve root is pulled from the spinal cord (a.k.a. avulsion). Currently, there is no reliable technique to restore continuity between an avulsed nerve root and the spinal cord. Surgery can bypass the injury as discussed later.

Ancillary Testing

Electrodiagnostic testing has a minimal role on brachial plexus birth palsies. The uncooperative infant is unable to tolerate the examination, requires sedation, and cannot follow instructions. Electrodiagnostic studies, including nerve conduction velocity and needle electromyography, overestimates clinical recovery in the proximal muscles of the shoulder and arm. This incorrect prediction provides false hope to the parents and delays referral for surgical intervention.

Radiologic studies can provide usually information by identifying nerve root avulsion injuries. The presence of a pseudomeningocele, a meningeal pouch filled with cerebrospinal fluid that extends through the intervertebral foramen into the paraspinal area infers a nerve root avulsion ( Fig. 12.3 ). This pouch represents an extraction of the dural and arachnoidal sleeve through the intervertebral foramen that often occurs during a root avulsion injury. CT myelography and magnetic resonance imaging have greater than 90% true positive rates for determining avulsion injuries correlated at surgery when pseudomeningoceles are seen. Smaller pseudomeningoceles may represent a false positive with preservation of nerve root integrity. Unfortunately, current imaging studies are unable to assess whether the neuroma has axons incontinuity or there has been complete axonal disruption.

Coronal MRI reveals right-sided pseudomeningoceles that have formed outside the intervertebral foramen indicative of root avulsion injury.

Courtesy of Shriners Hospital for Children, Philadelphia.

Timing of Surgery

The timing of surgery is dependent upon the degree and extent of injury. Mild plexus injuries (neurapraxias) recover quickly via remyelination without Wallerian degeneration. This process occurs in the first 6–8 weeks of life and does not require surgery. Moderate injuries (axonotmesis) recover more slowly following Wallerian degeneration and axonal regeneration. This process occurs at a rate of 1–3 mm per day and results in signs of clinical recovery between 3 and 6 months. The proximal muscles will recover first followed by the more distal muscles. Neurotmesis (rupture or avulsion) will not recover and requires surgical intervention.

The quandary in brachial plexus birth palsies is determining when to intervene. Surgery must have a positive effect compared to the natural history of recover. Global injuries with a Horner’s syndrome (Narakas 4) require early surgery within the first 3–4 months of life. The injury pattern is a combination of ruptures and avulsions that requires surgical reconstruction with nerve grafting and nerve transfers.

The Narakas 1 (C5 and C6) and 2 (C5, C6, and C7) injury patterns are more controversial regarding timing and technique of nerve surgery. There is no universal consensus regarding indications and timing of surgical intervention. Ancillary testing is unreliable in determining the exact extent of injury. We prefer serial examinations every 4–6 weeks to assess recovery. The active movement scale is measured and documented. Failure to demonstrate noteworthy signs of recovery by 5–8 months is an indication for surgeries. Injuries with no recovery or minimal recovery require surgery. In addition, injuries that demonstrate some early recovery but the process subsequently stagnates require surgery.