Brachial Plexus Birth Injury: Treatment and Interventions

Abstract

Introduction: Brachial plexus birth injury (BPBI) is a condition affecting newborns and involves damage to the nerve fibers compromising the brachial plexus during birth. Although most newborns recover spontaneously, a large subset require surgery to regain function, and others will have permanent disability despite intervention. Deciding when to pursue surgical intervention remains a challenge for clinicians treating BPBI. Methods: A comprehensive search of the literature was conducted using PubMed, Scopus, and MEDLINE databases. A total of 24 primary and secondary sources were chosen for inclusion following full-text assessments. All sources were analyzed to provide a comprehensive review on the development of BPBI treatments and interventions over time. Results: Spontaneous recovery can be achieved in many cases of BPBI, but most patients require physical therapy and other forms of treatment to avoid muscle imbalance and prevent contracture formation. In addition to physical therapy, the most common non-surgical interventions include botulinum toxin injections and splinting. In cases requiring surgery, clinicians may use several tests and diagnostic imaging to aid in decision making. Common surgical interventions for BPBI include nerve grafting, nerve transfers, and muscle and tendon transfers. Conclusion: Most newborns recover from BPBI within the first 3 months of life. However, some require treatment to restore optimal function. In general, non-surgical interventions should be the primary course of treatment, and surgery should be avoided unless the patient is deemed unable to recover with any other treatment.

Introduction

Brachial plexus birth injury (BPBI) occurs during birth and damages the nerve fibers compromising the brachial plexus. Incidence across countries varies between 0.5 and 3 for every 1000 live births. ¹ Most patients recover within the first 3 months of life. Surgery is necessary for others to regain function, but many of those will sustain some degree of permanent injury. ² Higher incidence of BPBI occurs with vacuum or forceps delivery, larger birth weight, gestational diabetes, and shoulder dystocia. ³ A caesarean section delivery diminishes the likelihood of BPBI; however, it does not fully prohibit its occurrence. ⁴ Albeit uncommon, 1% of all reported BPBI cases occur during delivery by caesarean section. ⁴ The nerve roots that are most commonly involved in BPBI are C5 and C6. Lesions to the C5 and C6 roots primarily affect the shoulder abductors, internal rotators, and forearm flexor muscles. If C7 is also injured, then the triceps and wrist extensors are additionally affected. ⁵ Total plexus palsy, an injury affecting C5-T1, presents as a flaccid and flail limb. ⁴ The progression of total plexus palsy varies depending on the nature of the injury. While cases involving a neurapraxic T1 injury may demonstrate spontaneous recovery, others may progress to total limb paralysis if left untreated. The two most important factors for spontaneous recovery are nerve root involvement and spontaneous recovery of the biceps by 4 months of age. The progression of the injury and recovery time depends on the severity of the nerve traction injury. ⁴ About two-thirds of patients have sufficient spontaneous nerve recovery, such that primary nerve reconstruction is not required. Physical therapy is required in all infants and should be initiated soon after birth to maintain passive range of motion (ROM) while the nerves are recovering. ⁵

Treatment and Intervention

Physical Therapy

BPBI patients often experience impairments in passive range of all motions, with supination and shoulder external rotation being the most common. Theories of why this occurs include: strength imbalance between recovered muscles and muscles with injured nerves, relative agnosia affecting development during recovery of joint sensation and movements, direct shoulder capsular injury during birth, and imbalanced functional reinnervation of some muscles. ⁶

Balanced regrowth of the shoulder can be compromised if the internal shoulder rotator muscles over-dominate the external shoulder rotator muscles. ⁶ Internal rotation contracture and skeletal changes can significantly compromise the patient's recovery by preventing full ROM or recovered muscle action. In such cases, the scapula tends to be elevated and anteriorly rotated, and the deformity appears early in infancy. If left untreated, the injury can progress into hypoplasia, retroversion, biconcavity or convexity of the glenoid, and/or flattening and subluxation of the humeral head; therefore, prompt treatment is essential.

As mentioned previously, the great majority of BPBIs affect the upper plexus and recover spontaneously. However, 60% to 80% of patients with upper plexus injuries and persistent motor deficits beyond 3 to 6 months of age present with glenohumeral dysplasia. ⁷ Early identification of patients with glenohumeral instability is vital to early implementation of corrective strategies and may minimize the risk of long-term shoulder dysfunction.

On inspection of the shoulder, BPBI children with glenohumeral dysplasia may have an internally rotated posture, asymmetry of the soft tissue folds near the axilla, and apparent shortening of the humeral segment. ⁷ Clinical examination should assess passive ROM for shoulder external and internal rotation with the arm abducted and adducted. As stated by Zuo et al, ⁷ the loss of passive external rotation beyond neutral with the elbow flexed and the scapula stabilized against the thorax is indicative of glenohumeral dysplasia. Tightness of the internal rotators and a posteriorly displaced humeral head also suggest glenohumeral instability.

Coupled with physical examination, diagnostic imaging of the shoulder is a helpful tool in screening BPBI children for glenohumeral dysplasia. Ultrasonography with a high-resolution linear transducer is the study of choice in infants 3 to 6 months of age due to its ability to provide clear visualization of the cartilaginous glenoid. ⁷ Glenohumeral joint alignment can be reliably quantified by the examiner, with the literature reporting high rates of intraobserver and interobserver consistency.

While ultrasonography is the preferred method of screening for glenohumeral dysplasia, MRI is often utilized for complete evaluation and surgical decision-making. ⁷ The severity of glenohumeral dysplasia can then be graded using the Waters classification. The grade of dysplasia, as well as clinical and/or radiologic evidence of glenohumeral instability, may justify a recommendation of stretching and/or splinting. Mild cases with a high likelihood of recovery may only require stretching, while more severe cases warrant splinting to prevent contracture of the internal rotators.

Specific physical therapy strategies for the shoulder often include stretching to maintain full passive glenohumeral ROM, encouragement of active motion, constraint induced movement therapy, and electrical stimulation. ⁶ Physical therapy is important in the recovery of BPBI patients, but there are differing results regarding its efficacy. ⁵ There is data to suggest that exercises increase plasticity in the spinal cord and central area through ependymal cell proliferation. Consequently, this alters the representation of body parts in the motor cortex, and plasticity increases due to increased sensory input after exercises. There is further evidence to show that cortical modeling can increase through exercises following hand injuries. However, a study conducted by Sahin and Karahan ⁵ in 2018 demonstrated that although exercises positively affect recovery rate and prevent possible complications, the intensity and frequency of the exercises do not significantly impact recovery.

Stretching and ROM

Unless the clavicle or humerus is fractured, immobilization is not advised. ⁸ Physical therapy exercises should be started immediately and performed several times per day to prevent contractions at the shoulder, elbow, and wrist. An exercise program may begin with passive ROM exercises for all joints of the upper extremities, followed by active ROM and muscle enhancement exercises in the subsequent months. ⁵ Patients with lower plexus palsies who develop early contractures of the hand and do not improve with physical therapy should be placed in a wrist/hand splint with the thumb in opposition. Additionally, a shoulder external rotation splint may help to prevent internal rotation contracture at the shoulder. ⁸

Botulinum Toxin and Splinting

BPBI patients with functional limitations resulting from restricted shoulder and elbow movement may benefit from receiving Botox injection during recovery. ⁸ When brachial plexus lesions cause differential muscle weakening, the imbalance between muscle groups across a common joint often leads to movement restrictions. These restrictions result from improper coactivation between agonist and antagonist muscle groups during neuromuscular healing, or a power imbalance due to sustained weakness of one muscle group in relation to the other, which can also lead to structural joint deformities.

Botox injections into strong antagonist muscles can increase coordinated muscle balance in BPBI patients. ⁹ Clinical evidence of muscle group imbalance is the most important criterion for selecting patients for Botox treatment. The temporary weakening of the strong antagonist muscles, discriminating in favor of the agonist muscles, may contribute to better muscular balance by strengthening agonist muscles peripherally or by promoting motor learning at the level of the central nervous system. Improvement in Active Movement Scale (AMS) scores can begin at 1-2 months and last until after a full year of treatment. However, greater improvement in scores is more likely at 1-2 months, possibly due to wearing effects of Botox. Indications for use are (1) minimal improvement over time in AMS scores for flexion of the elbow in the face of improvement in other movements and (2) evidence of co-contraction limiting effective movement on physical examination. ⁹

Treatment using botulinum toxin is similarly indicated for infants with internal contracture of the shoulder. ¹⁰ This procedure temporarily denervates the internal rotators as neuronal recovery takes place in the shoulder abductors and external rotators. However, Botox alone is often insufficient for recovery of shoulder motion. Physical therapy and splinting should be implemented in conjunction with Botox injection 2 to 3 times over the course of 18 months for full therapeutic effect ⁸ (Figure 1).

Figure 1.

Infant boy with recovering C5-C6 brachial plexus palsy who developed very tight internal rotation. His internal rotators were temporarily paralyzed with botulinum neurotoxin, and he was placed in a cast for shoulder external rotation while his rotator cuff recovered.

Verchere et al ⁶ performed a retrospective review of splinting in BPBI patients to assess how splinting impacts recovery. The first splint used in the study was a betapile torso suit that was created to stabilize shoulder rotation by anchoring the humerus to the bodysuit with a Velcro strap. This method produced improvements in external rotation and supination, but patients displayed low compliance due to extreme discomfort resulting from high temperatures. In response, Verchere et al ⁶ created a custom volar thermoplastic elbow extension splint. This splint is called the “Sup-ER” splint, as it was designed to hold the affected limb in full forearm supination (Sup) and shoulder external rotation (ER). Medical imaging confirmed the ability of the Sup-ER splint to reposition the glenohumeral joint and maintain congruity, even in patients who presented with ultrasound-confirmed posterior subluxation in the resting position out of the splint. The authors recommend beginning Sup-ER splint use at around 6 weeks of age, with the recommended duration ranging from 8 to 12 months. ⁶ It is important to note that the Sup-Er splint is only one of many options for splinting. Many centers have moved towards a “teapot” style splint to hold the shoulder in external rotation and adduction. ¹¹ The posture achieved with a teapot splint provides stable reduction of the glenohumeral joint.

Efficacy of splint use is dependent upon family compliance and beginning the splinting process before 3 months of age. ⁶ Furthermore, it is important to identify patients who have an internal rotation imbalance greater than the splint can correct by 4 months of age. In these situations, patients can be administered a Botox injection to the pectoralis major and subscapularis, as well as temporary application of an external rotation spica cast for about 4 weeks. Following the removal of the spica cast, the patient may be returned to a Sup-ER splint or another similar splint.

It is vital to start the splinting process early as babies 6 months and older can begin to overpower the splint. ⁶ Physical therapy should be used in addition to splinting as to prevent joint contractures, strengthen recovering muscles, promote the development of sensory stimulation, and improve developmental milestones in the presence of incomplete neuromuscular function.

Surgical Decision Making

Modern guidelines for management of BPBI evolved out of a report by Gilbert and Tassin ¹² in 1984. The authors evaluated nonoperative cases and concluded that if elbow flexion and deltoid contraction had not started by 3 months of age, ultimate function was likely to be poor.^12,13 In this way, the report created the original standard for predicting upper extremity recovery, with elbow function at 3 months as the main criterion for surgical intervention. This standard was further refined by Dr Clarke et al ¹⁴ at the Hospital for Sick Children in Toronto to avoid operating on patients with injuries that may otherwise recover spontaneously.

Dr Clarke et al ¹⁴ developed the Test Score to consider elbow flexion, elbow extension, and wrist, thumb, and finger extension, essentially testing function of the C5-C8 nerve roots. The Test Score is determined by calculating values from the AMS and adding the total converted scores for the 5 previously stated movements. The AMS classifies motion without (0-4) or against (5-7) gravity for these 5 motions and then assigns a score from 0 to 2.0, with AMS values of 3-5 given a score of 0.6 and an AMS value of 6 given a value of 1.3 (Table 1). The tally of all 5 determines the Test Score, with values <3.5 being strongly predictive of poor recovery without surgical intervention. Test Scores are acquired at 3 months of age for early determination of the need for surgical intervention.

Table 1.

Brachial Plexus and Upper Extremity Examination.

Joints (R/L)	Movements	Position	AMS Score	Converted Test Score
Shoulder	Abduction, Adduction, Flexion, Internal Rotation, External Rotation	Supine: gravity eliminated shoulder abduction and adduction Side-lying: gravity eliminated shoulder flexion, elbow flexion and extension Sitting: all remaining movements	0 1 – 2 3 – 5 6 7	0 0.3 0.6 1.3 2.0
Elbow	Flexion, Extension
Wrist, Fingers, and Thumb	Extension, Flexion, Intrinsic Function
Forearm	Pronation, Supination

Table 1 lists the brachial plexus examination by upper extremity movements. ¹⁵ Each joint is examined separately and in different planes to assess the contribution of gravity. However, the AMS calculations for determining the converted test score, as described by Clarke et al, ¹⁴ only take into account the elbow, wrist, fingers, and thumb extension to predict the need for surgery.

As explained by Cawthorn et al, ¹⁶ a single age, score, or criterion is inadequate for identifying patients requiring surgical management. Algorithms for BPBI assessment have evolved greatly over the years and continue to evolve. The most recent iteration developed by the Sick Kids Hospital calls for initial intake assessment by a physiotherapist prior to 3 months of age. Infants with suspected BPBI are evaluated for passive ROM and using the AMS. Based on the initial assessment, the physiotherapist decides whether the child would benefit from dynamic ultrasound imaging of the shoulder, early supination-external rotation (Sup-ER) splinting of the shoulder, and/or evaluation by the full team prior to 3 months of age.

Most infants with BPBIs are referred for a multidisciplinary clinic appointment by 3 months of age, during which ROM and AMS scores are evaluated again. ¹⁶ Cawthorn et al ¹⁶ identify a converted AMS score less than 3.5 or a completely flail extremity as indicators for primary nerve surgery at or before 3 months of age. Infants that do not meet criteria for surgery at this point will be reassessed at 6 months of age. Indications for primary nerve surgery at 6 months include a lack of significant improvement in AMS scores, as indicated by an elbow flexion score less than 3. Infants who have shown improvement in AMS scores return for a third multidisciplinary follow-up at 9 months of age, during which a final decision regarding surgical intervention is made. The Sick Kids Hospital algorithm uses the “cookie test,” which requires infants to bring a cookie to their mouth while the shoulder is held in adduction and with less than 45 degrees of neck flexion (Figure 2). ¹⁴ A positive response to this test confirms a functioning degree of shoulder external rotation, elbow flexion, hand supination, and finger pincer motion. An inability to pass the test results in a recommendation of primary nerve surgery.

Figure 2.

“Cookie Test” developed by Howard Clarke as a method to assess global upper extremity function at 9 months of age and predict meaningful spontaneous recovery.

Not all cases of BPBI follow the algorithm above. In cases of upper plexus palsies, efforts are made to manage the condition nonoperatively, typically through a combination of Sup-ER splinting, botulinum toxin, and casting. ¹⁴ If nonoperative methods of treatment are inadequate, infants will display poor recovery of active external rotation and persistent dysplasia/posterior subluxation of the glenohumeral joint. As a result of improper glenohumeral joint positioning, elbow flexion will be limited. In severe cases, infants may require primary nerve operation followed by surgical management of the shoulder joint. More mild cases can be managed using surgical management of the shoulder joint and physical therapy alone.

In reviews of different approaches to surgical decision making, it is commonly agreed upon that surgical decision making is crucial in patients aged 3-6 months. ² Many infants undergo diagnostic imaging as a part of the surgical decision-making process. ¹⁴ Imaging studies often provide useful insight pertaining to the potential for spontaneously recovery, the need for surgery, and/or the timing of surgery. Two frequently used diagnostic imaging studies for BPBI infants include diaphragmatic ultrasound and computed tomography (CT) myelogram. The diaphragmatic ultrasound is used to assess function of the phrenic nerves, while the CT myelogram can provide information regarding the presence or absence of pseudomeningoceles. CT myelogram findings provide useful information for preoperative planning, as pseudomeningoceles often serve as surrogate markers for nerve avulsion, though this association has been challenged as of late. ¹⁷

The earlier a decision can be made about surgery, the better the outcome tends to be. If a decision is delayed past 6 months, muscle stability, shoulder strength, and proper bone formation at the shoulder may be at risk. Infants who recover partial antigravity upper trunk muscle strength in the first 2 months of life are expected to show full recovery, while infants who do not recover antigravity biceps strength by 5 months may require microsurgical resection of the brachial plexus. ¹ Nerve repair surgery is recommended if an upper plexus lesion is present and if bicep function does not surpass antigravity movement at an age of 3 months. Surgical exploration is highly recommended for children who display signs of Horner's syndrome as well. ¹⁴

Although microsurgical nerve reconstruction is most frequently advocated for BPBI patients between 3 and 9 months of age, recent studies show an indication for surgery at later ages as well. In fact, the Treatment and Outcomes of Brachial Plexus Birth Injury (TOBI) Study Group ¹⁸ found improvements in shoulder and elbow function following microsurgical nerve grafting and nerve transfers in children older than 9 months. Other studies in the literature highlight similar findings, necessitating constant reevaluation and updating of BPBI algorithms.

In all cases, the decision to pursue surgical intervention should be made with careful consideration. As explained by Zuo et al, ⁷ early surgical intervention for children with upper trunk injury may not result in greater outcomes than spontaneous recovery; therefore, longer periods of observation may be warranted at times.

Nerve Grafting

Early studies suggested 3 months as the latest age for nerve grafting to maximize the patient's functional recovery.^12,19 If it is clear a child requires nerve grafting, early microsurgery of the brachial plexus provides the best results. In many cases, spontaneous recovery is still unknown at 3 months, thus limiting the usefulness of grafting. A telling sign for surgery is if the muscles innervated by the upper roots are delayed past 3 months, for at this point, root disruption is likely. ¹⁹

If recovery does not start until 5 months, functional impairment at the end stage will remain. ²⁰ Other studies have also found that beyond 4 months, the chance of spontaneous recovery of the biceps muscle is significantly diminished. ²¹ However, data differing from the above studies exists. One study shows that when no operations were performed until the patients were 5 months of age, 71% of the patients without bicep function at 3 months attained bicep contraction by the age of 6 months. ²² Surgical planning can be navigated by the 4 main subtypes of injury based on the type of delivery and type of paralysis at 1 month.

Nerve Transfers

Nerve transfers are considered in cases where direct repair is not possible or sufficient functional recovery with direct reconstruction or nerve grafting is not expected. ²³ Nerve transfers allow for reconstruction of motor deficits with purely motor nerves with a single coaptation. This treatment approach permits faster reinnervation of the muscle and should be implemented in cases of root avulsion. The most common procedures include: spinal accessory nerve transfer, intercostal nerve transfer, Oberlin transfer, and medial pectoral nerve transfer to the musculocutaneous nerve. When available, the spinal accessory to suprascapular nerve and intercostal to musculocutaneous nerve transfers are recommended for regaining shoulder function and elbow flexion in patients with C5-C6 injuries. The Oberlin transfer may also help restore elbow flexion. Otherwise known as the double fascicular transfer, the Oberlin transfer entails reconstructing the biceps nerve using donor fascicles from the ulnar nerve at the level of the brachium. Procedures that are no longer indicated due to high risk include hypoglossal nerve transfer and phrenic nerve transfer. ²³ Contralateral C7 transfers, though previously contraindicated, are now utilized with caution for reconstruction of wrist and hand function in select cases.

Muscle and Tendon Transfers

The decision to perform tendon transfers is highly nuanced and relies on careful consideration of a patient's limb functioning and goals of care. In carefully identified cases, tendon transfers may be used to restore wrist and digital extension if function is lost ²³ (Figure 3). Neuroma excision and sural nerve grafting are indicated if no elbow flexion is present at 3 months. ²³ If internal rotation contracture of the shoulder is left untreated in BPBI, the patient will suffer from posterior shoulder subluxation or dislocation secondary to varying degrees of glenohumeral bony deformity. The most common treatment for this involves the release of the subscapularis tendon, with or without the release of the pectoralis major tendon, and transfer of the latissimus dorsi and teres major tendon to restore shoulder external rotation. ²⁴ Many patients benefit from this procedure through increased range of external shoulder rotation and abduction, though the improvement in external rotation comes at the expense of internal rotation. The latissimus dorsi and teres major transfer to rotator cuff, along with the release of the pectoralis major, has a long-term increase on active external rotation of 45 degrees. Another beneficial procedure to increase shoulder abduction stems from the theory of co-contraction. The procedure allows for co-contraction between agonist and antagonist muscles while they’re recovering, leading to restriction of particular movements across the shoulder joint. ⁸ An alternative option involves using the lower 2/3 of the trapezius muscle for transfer to the infraspinatous to power shoulder external rotation.

Figure 3.

Secondary reconstruction of a 5-year-old boy with an untreated, incomplete C7-C8 and T1 brachial plexus birth injury. (A) Pre-operative examination with wrist drop. (B) Demonstrating the wrist can be passively extended. (C) Early post-operative photo after tendon transfers to restore wrist balance and intrinsic function including pronator teres to ECRB and brachioradialis pinch plasty with free tendon graft.

Conclusion

BPBI is an injury that occurs during childbirth with the potential to produce life-long effects. The degree of lasting damage depends on the type of injury and course of treatment, and a successful treatment outcome is also dependent upon patient compliance. However, each case is unique and requires an intervention that most appropriately corresponds with the severity of injury. Spontaneous recovery can be achieved by most BPBI patients, but many patients undergo physical therapy, Botox, and splinting treatments in order to prevent contracture formation and avoid muscle imbalance. ⁵ In some cases, surgical intervention is necessary.

While BPBI patients experience losses in passive range of all motions, supination and shoulder external rotation impairment are particularly common. Balanced regrowth of the shoulder can be compromised if the internal shoulder rotator muscles over-dominate the external shoulder rotator muscles. Internal rotation contracture and skeletal changes can significantly compromise the patient's recovery by preventing full ROM or recovered muscle action. ⁶ Unless the clavicle or humerus is fractured, immobilization is not advised. Physical therapy exercises should be started immediately and performed several times per day to prevent contractions at the shoulder, elbow, and wrist. Treatment using botulinum toxin is indicated for infants with internal contracture of the shoulder. ⁸ Patients who develop early contractures of the hand or shoulder and do not improve with regular physical therapy should be placed in a wrist/hand splint with thumb in opposition and/or a shoulder external rotation splint, respectively. ⁸

It is commonly agreed upon that surgical decision making is crucial in patients aged 3-6 months. ¹ A Test Score lower than 3.5 at 9 months of age is a reliable indication that surgical intervention is necessary. Different surgical approaches are taken for different patients, including nerve grafting, nerve transfers, or muscle and tendon transfers. However, non-surgical interventions should be the primary course of treatment, and surgery should be avoided until it is relatively clear that the patient will not recover with any other treatment.