Clinical manifestations

Presentation and course

Injury to the brachial plexus can be classified by the anatomic localization of the nerves affected, such as the upper, lower, or total plexus. Erb (or Erb-Duchenne) palsy, being the most common form of brachial plexus palsy in neonates, is caused by disruption of the upper brachial plexus nerves at cervical nerve roots 5 and 6, and possibly 7 (C5–C7) (105). Clinical findings for C5-C6 palsy include shoulder muscle paralysis with an asymmetric Moro reflex, an internally rotated upper arm, an extended elbow due to flexor paralysis, a pronated forearm, and a flexed wrist (64; 80; 170). If C7 is also involved, the baby may have a “waiter's tip” posture with adduction and inward rotation at the shoulder, extension and pronation at the elbow, and flexion of the fingers (64; 170). In children with an upper plexus lesion, in addition to the motor deficits, the sensibility of the thumb and index finger is diminished, which has a significant negative impact on hand function (24).

Klumpke palsy is a less common form of brachial plexus palsy in neonates and is caused by involvement of the brachial plexus at cervical roots 7 and 8 and thoracic root 1 (C7-C8, T1) (105). Classic clinical signs include a supinated forearm with a flexed wrist and fingers, a “claw hand.” These patients have absence of the grasp reflex on examination (80). In lower brachial plexus palsy, the involvement of the sympathetic nerves from the first thoracic root, which gives rise to the superior cervical sympathetic ganglion, can result in ipsilateral Horner syndrome manifested by ipsilateral constricted pupil, upper lid ptosis, and facial anhidrosis. However, total brachial plexus palsy is often called "Klumpke" palsy as the patient presents with a lesion of C7-T1, but total brachial plexus palsy is always associated with an upper spinal nerve lesion of varying severity (118). Obstetrical-induced Klumpke palsy with only a paralyzed hand is extremely rare (09).

The phrenic nerve, arising from C3, C4, and C5 can be involved in brachial plexus palsy with resultant ipsilateral diaphragmatic paralysis, causing a decrease in thoracic space, tidal volume, and vital capacity. The neonate can develop tachypnea, cyanosis, and inefficient ventilation (07; 35). If brachial plexus palsy is associated with injury to cervical spinal cord, the patient may be unable to breathe, resulting in subsequent ventilator dependence or death (35; 144).

Among newborns born vaginally by breech or cephalic presentation, those born breech are more likely to develop Erb palsy, whereas those in the cephalic group are more likely to have total brachial plexus palsy (10). Breech infants have a higher frequency of bilateral obstetrical brachial plexus palsies and concurrent phrenic nerve palsy (10). Concurrent phrenic nerve palsy in neonates with brachial plexus palsy is a strong negative prognostic indicator for spontaneous motor recovery of the brachial plexus, particularly after vertex delivery (176). In contrast, concurrent Horner syndrome in neonates with brachial plexus palsy has no prognostic value in predicting poor spontaneous motor recovery in patients with total-type brachial plexus palsy (177).

For nondiabetic mothers who deliver vaginally, neonatal BW 4400 g or greater was associated with a significant increase in the adverse neonatal outcomes of shoulder dystocia or brachial plexus injury, whereas neonatal BW 4800 g or greater was associated with a significant increase in the adverse maternal outcomes of postpartum hemorrhage or third- or fourth-degree perineal tears (11).

Prognosis and complications

Prognosis. The prognosis and natural history of neonatal brachial plexus palsy depends on the extent of the initial injury. The pure forms of Erb-Duchenne palsy (ie, C5-C6) and pan-plexus palsy have a higher incidence of nerve avulsions than the extensive form of Erb palsy (ie, C5-C7) (162). Rapid and useful motor recovery is typical with Erb-Duchenne palsy and the upper root levels (C5 and C6) of pan-plexus palsy, in contrast to the poor prognosis of motor recovery with lesions of the lower root levels (C8 and T1) of pan-plexus palsy (156). Recovery of sensory function is much more frequent and occurs to a greater degree than recovery of motor function (156).

The prognosis and natural history depend, at least in some cases, on various circumstances of delivery (10). For example, spontaneous recovery of shoulder abduction and elbow flexion in newborns with Erb palsy is significantly worse among those with vaginal deliveries who were born breech compared with those born with cephalic presentations (59; 10). Obstetric brachial plexus palsy after a breech delivery is more typically the result of avulsion of the upper roots, an injury that cannot be treated satisfactorily by microsurgical grafting and carries a considerably worse prognosis for shoulder function (162; 59).

Determination of whether the injury is preganglionic or postganglionic through imaging and clinical exam can help predict the extent of motor recovery (70). Usually, preganglionic avulsion injuries are less likely to spontaneously recover motor function without surgical intervention. Injury to the phrenic, long thoracic, dorsal scapular, scapular, sympathetic chain, or the thoracodorsal nerve portends a poor recovery (70).

The Mallet Classification is a widely used tool that categorizes motor function of the shoulder to degrees of brachial plexus injury. The Mallet score looks at movement of the hand to mouth, neck, and spine and global abduction and external rotation. The lowest score given for no function is 1, and the score for normal function is 5. Summation of all these movement scores gives the overall Mallet score (123). In approximately 20% of cases, the Mallet score cannot be applied because of a discrepancy between the deficiency of shoulder abduction and shoulder external rotation (08). On this basis, Al-Qattand and El-Sayed concluded that “documenting the deficits in shoulder abduction and external rotation are best done separately and this can be accomplished by using other grading systems” (08). Narakas and colleagues also developed a classification of brachial plexus injury for infants aged 3 weeks and older for predicting the prognosis of spontaneous recovery depending on the severity of the brachial plexus injury, which is a strong predictor of outcome (118; 143; 55; 70). In the Narakas classification, poor recovery was less than half the normal range for elbow flexion and shoulder abduction (118). Narakas and colleagues found that Group I with Erb palsy (C5-6 injuries) had the best prognosis and occurred most commonly. Group II with C5-7 injuries had a poorer prognosis than Group I. Group III had involvement of C5-T1 and presented with a flail extremity, and Group IV with Horner syndrome in addition to C5-T1 involvement occurred in 4% of cases and had the worst prognosis.

When elbow flexion is considered in isolation, elbow flexion recovers spontaneously except in rare cases, although recovery occurs later in more severe injuries (74). On this basis, the authors considered it doubtful that nerve reconstruction could improve elbow flexion more than the likely spontaneous recovery in infants with obstetric brachial plexus injuries (74), although such procedures are increasingly being recommended (111; 115).

In a systematic review of brachial plexus palsy that included studies reported from 1966 to 2001, Pondaag and colleagues concluded that recovery occurs in approximately 70% to 80% of patients, with the remaining patients having residual deficits (128). The majority of patients with brachial plexus palsy diagnosed at birth should recover from the neurologic deficit (06; 128). However, those who did not recover during the 3- to 6-month period would require surgical intervention.

In a population-based study of 38,749 births during 1999 to 2001, Lagerkvist and colleagues reported that the incidence of brachial plexus palsy was 2.9 per 1000 live births (93). By 18 months, most infants had recovered with only 18% showing persistent brachial plexus palsy. At 3 months of age, the predictive value of regained elbow flexion, shoulder external rotation, and forearm supination for complete recovery was 100%, 99%, and 96%, respectively. Noetzel followed 80 patients with brachial plexus palsy who did not recover by 2 weeks of age and noted complete recovery was seen in 66% of patients by 6 months of age. Nine percent of patients demonstrated 3/5 strength in the triceps and biceps by 6 months and had residual weakness of 4/5 strength in triceps and biceps. Fourteen percent of subjects continued to have severe weakness in all muscle groups and were not antigravity by 6 months (113). Foad and colleagues performed an evidence-based review summarizing the data regarding prognosis using the Narakas classification and found that approximately 64% of group I and II have spontaneous recovery of biceps function at 3 months of age; this is consistent with conclusions from other studies that saw spontaneous recovery rates of approximately 66% (113; 77; 128; 55).

The decision to proceed with surgery for brachial plexus palsy is usually made by 6 months of life and is based on the clinical course as well as imaging findings suggestive of a poor prognosis for recovery. Depending on the severity of the injury and whether the distal basal lamina tubes remain intact, total recovery may occur in weeks or months (100). The distance between the proximal and distal stumps that the nerve axon must sprout determines the length of time for recovery. Spontaneous recovery is usually seen within the first 3 to 4 months after injury (100). By the age of 2 to 3 months, poor hand function is an absolute indication for surgical intervention (126; 100). Pondaag and colleagues also recommend surgery for patients who do not recover external rotation of the shoulder and elbow flexion or forearm supination by the age of 4 months (125). Clarke and Curtis recommended surgical exploration by 9 months if the patient is unable to place a cookie in the mouth with no more than 45 degrees of neck flexion, hence, a failed cookie test (118).

The specific surgical intervention depends on intraoperative electromyographic evaluations and visual observations of the brachial plexus. Surgical options for the patient are exploration and at times neurophysiologic testing in cases of neuroma-in-continuity with expectant management, neurolysis wherein the nerves are freed from inflammatory adhesions, neuroma excision and end-to-end anastomosis of the same nerve, and nerve grafting with local nerve by end-to-end anastomosis or remote nerves using sural nerve transplant or intrabrachial plexus transplant donor nerves (23; 63; 92).

Complications. Consequences of untreated neonatal brachial plexus injury may affect the glenohumeral joint of the shoulder and other joints of the arm as well as hand and finger function. The late sequelae include glenoid deformity or posterior dislocation of the glenohumeral joint (86). Neonatal brachial plexus injuries also result in structural changes in the affected limb bones, a finding found also in animal models, but these changes may be diminished if the microsurgical reinnervation is accomplished early enough (66). The most common deformities are limb length discrepancy, the development of contractures at the shoulder, elbow, and forearm as well as ulnar deviation of the wrist, and paralysis of the fingers (137; 68; 04). Zancolli and colleagues found that in 148 patients, the most common deformity was internal rotation contracture of the shoulder (72%) followed by supination contracture of the forearm (69%) and flexion contracture of the elbow (62%) (178). The amount of intraoperative correction is significantly associated with higher self-confidence and normal activities of daily living (71).

Approximately two thirds of the children (69%) develop a glenohumeral abduction contracture; it is more common in those with upper neonatal brachial plexus injury (04).

Muscle denervation and degeneration are also complications of neonatal brachial plexus palsy. The most affected muscle is the subscapularis muscle, and its structural abnormality correlated with the degree of glenoid version (79). Abnormal rotator cuff muscles also correlated with posterior subluxation of the humeral head and the shape of the glenoid. The supraspinatus muscle differences correlated with the degree of superior subluxation of the humerus (79).

Neonatal brachial plexus has a negative influence on upper limb function and quality of life, and it has lifelong implications and impacts on a patient’s choices regarding education and profession as well as on work performance (164; 106).

Clinical vignette

Case 1 (unilateral Erb-Duchenne paralysis). A 4490 g male neonate was delivered via spontaneous vaginal delivery with no apparent complication. However, immediately after birth it was noticed that the baby did not spontaneously move his right arm. Initially his arm was flaccid, but over time it became clear that his distal function was good and proximally he was weak.

He presented to the clinic at 2 years of age for evaluation and possible treatment. He had worked with physical therapy, and the flexion in his arm had improved, but he still had considerable trouble elevating and externally rotating his arm. MRI showed right-sided pseudomeningoceles at the C5-C6 and C6-C7 lateral recesses that extended into the neural foramina with preservation of the right C6 and C7 nerve roots within the pseudomeningoceles. Spinal cord signal intensity and appearance remained normal.

Case 2 (bilateral Klumpke paralysis). JM presented to Boston Children’s Hospital at 7 months of age with the residua of bilateral Klumpke obstetric palsy (161). He was born on May 30, 1902, following a difficult labor. When the physician, JM Wells, arrived after 12 hours of labor, there was a face presentation with the chin posterior. Chloroform was given to complete relaxation, but the head could not be flexed. Application of forceps was tried, “but as there was absolutely no ‘give’ this was quickly discarded.” Several attempts were made at a version, and on the third attempt “the occiput engaged, and the labor proceeded normally, the right shoulder presenting at the pubes.” In the process, the attending physician noted that, “during one of the rests from the anesthetic, while I held my hand in the vagina with fingers against the chin using more or less pressure I heard and felt a decided click or snap. At first I thought the child’s neck was broken…” After delivery, the child was initially “narcotized by the chloroform but after slight artificial respiration came around all right.” When the child recovered from the anesthetic, the physician and the mother noticed that both arms hung limp from the shoulders without movement, whereas the head, neck, and legs moved normally. The child’s neck was examined, and no evidence of a fracture was identified.

He first moved his arms at the shoulders at 4 weeks. When he was examined on December 7, 1902 (approximately 6 months of age), his arms were abducted and internally rotated, the forearms flexed and pronated, the wrists somewhat extended, the fingers extended at the metacarpophalangeal joint and flexed distally, and the thumbs abducted to the plane of the hand. Passive extension at the elbow was “resisted with considerable force,” but the hands were flaccid. Voluntary motion of the upper extremities was limited to “elevation of the arms, and flexion of the forearms” (ie, the C5-6 myotomes). Movements of the head, neck, and legs were normal. Horner syndrome was not mentioned. The triceps reflex was absent bilaterally, but the knee jerks were normal. Pinprick sensation was present and judged normal in the upper extremities.

On February 4, 1903 (approximately 8 months of age), forearm flexion was “fair” (C5-6), the supinator muscles could be felt to contract (C6-7), the wrists could be slightly extended (C6-7), but deviated to the ulnar side, and slight movement had returned to the fingers of the left hand (except the middle finger) (probably C7-8 and not T1) and also the thumb and index finger of the right hand (probably C7-8 and not T1). Marked atrophy was noted in the forearm flexors (C7-8) and the intrinsic hand muscles (T1). The deltoids (C5), biceps (C5-6), and supinator (C6-7) muscles responded normally to electrical stimulation, whereas the triceps (C7-8) and all the muscles of the forearms (C7-8) and hands (T1) gave no response.

He learned to walk at about 1 year of age and had normal cognitive development. On the last reported examination in May 1905 (2 years of age), his gait was normal, but the paralysis of his arms had remained nearly the same, except that the grasp was somewhat stronger, especially on the left, though this was attributed to “recovery of the long flexor muscles, as the paralysis and wasting in the small muscles of the hand [was] still marked, and pronation of the forearms, flexion of the hands, and extension of the forearms [had] not improved, in spite of fairly regular treatment with massage and electricity.”

Biological basis

Anatomic localization

The brachial plexus is formed by the C5-T1 nerve roots and consists of roots, trunks, divisions, cords, and branches. The five cervico-thoracic nerve roots merge to form an upper, middle, and lower trunk, and each trunk divides into anterior and posterior divisions, using the axillary artery as the anatomical landmark. The six divisions then form three cords: the posterior cord that contains posterior divisions of C5-T1, the lateral cord that contains the anterior divisions of the upper and middle trunks of C5-7, and the medial cord, which contains the anterior division of the lower trunk. The most important branches are the musculocutaneous nerve that is formed from the lateral cord, the median nerve combined from the lateral and medial cord, the ulnar nerve from the medial cord, and the radial and axillary nerves from the posterior cord. The upper brachial plexus, C5 and C6, innervates the deltoid, spinati, biceps, brachioradialis, biceps supinator, and flexor muscles of the forearm (80; 170). The lower brachial plexus innervates the intrinsic muscles of the hand (73).

When examining a patient with a suspected brachial palsy, attention should be given to the position of the head, neck, and arm. Concurrent nonmuscular torticollis may develop in association with brachial plexus injury, with the head turned away from the affected arm (88; 16; 76). If present, palpate the sternocleidomastoid to feel for a contractured muscle or a pseudotumor (118). Brachial plexus palsy and associated torticollis do not affect the clinical progression of the disease, nor does it have bearing on the severity of the palsy (76). In fact, 63% of patients recovered with conservative management of their torticollis (76).

Next, the neck and arms should be evaluated for fractures of the clavicle, humeri, and ribs because a so-called "pseudoparalysis" can be mistaken for a true brachial plexus injury. Pseudoparalysis occurs when the brachial plexus is indirectly compressed by bone fragment, local swelling, or involuntary arm splinting (118). Evaluation of shoulder function is also important because posterior dislocation of the shoulder has been associated with brachial plexus palsy (53; 154). Evaluation of the shoulder includes passive and active range of motion and holding the arm in 90 degrees of abduction and adduction as well as internal and external rotation of the joint (86). Also, one can palpate the pectoralis major, latissimus dorsi, and teres muscle to evaluate the contractile force (86).

Moreover, total brachial plexus palsy may also result in atony and flexed posture of the fingers (118). The presence of finger movement in the setting of brachial plexus injury may later result in the development of posterior subluxation or dislocation of the humerus head due to imbalance of the muscles during development of the infant’s shoulder (110). With total brachial plexus palsy the presence of a Horner syndrome generally conveys a worse prognosis for functional recovery (118; 51).

Asymmetry of the Moro reflex and tonic neck reflex also indicates brachial plexus injury (123). The Moro reflex disappears around 6 months in healthy infants; it is elicited by sudden extension of the neck that causes shoulder abduction and elbow and digit extension as well as finger spreading. The asymmetric tonic neck reflex is elicited by turning the head to one side, which causes extension of the upper and lower extremities on the side to which the head is turned and contralateral upper and lower extremity flexion. Also, one should test for sensation to light touch and pain with nail bed pressure and observing for aversive movements in the affected hand (123).

Pathophysiology

Brachial plexus palsy occurs as a result of stretch, tear, avulsion, or compression of the nerves. Obstetric brachial plexus palsy can result from excessive lateral traction and forceful deviation of the fetal head from the axial plane of the fetal body, particularly in association with shoulder dystocia, which increases the necessary applied peak tractional force to the nerve roots exiting the spine and also increases the time to deliver the fetal shoulders (54; 72; 73; 44). Direct compression of the fetal shoulder on the symphysis pubis may also cause an injury to the brachial plexus (44).

The neuropathology of brachial plexus palsy was originally described by Seddon (138), who classified nerve injury as:

Neurapraxia (Class I). Damage to the nerve sheath where there is a block of nerve conduction. The axon and nerve elements are left intact. The potential for regeneration is present. Neurapraxia is the most common form of brachial plexus injury.

Axonotmesis (Class II). Disruption of the axon of the nerve where the endoneurium is disrupted. However, the neural sheath (perineurium and epineurium) is left intact. The potential for regeneration is present.

Neurotmesis (Class III). Complete disruption of the postganglionic nerve (endoneurium, perineurium, and epineurium are transected) (138).

Root avulsion. Complete disruption of the ganglia from the spinal cord at both the anterior and posterior roots.

Although complete recovery frequently occurs in brachial plexus palsy secondary to neurapraxia and axonotmesis, permanent loss of function occurs after root avulsion and neurotmesis if no surgical intervention is undertaken.

Sunderland’s first and second degrees of peripheral nerve injury agree with Seddon’s Class I and II, respectively. However, in 1951 Sunderland expanded on Seddon’s classification of nerve injury in regard to whether transection of the nerve involves the epineurium and perineurium in the setting of damaged endoneurium (155). In Sunderland’s fourth degree injury, perineurium is damaged, and in the fifth-degree injury the nerve is completely transected with epineurium being damaged as well (155). Spontaneous recovery is not possible without surgical intervention with these two injuries (120).

Cell biology of neuronal sprout growth. When a peripheral nerve is injured or transected, the part of the axon that is still attached to the cell body is called the proximal stump, and the other segment is called the distal stump. Nerve injury prompts the recruitment of Schwann cells and glial cells to the area to remove debris. The distal end undergoes a process called Wallerian degeneration where the myelin and damaged axon are broken down by the Schwann cells and macrophages and disappear. Only the endoneurium remains. The cell body undergoes chromatolysis where the nucleus moves to the periphery, and the Nissl bodies or the endoplasmic reticulum is dispersed. The proximal end swells and undergoes some degeneration as well in a retrograde fashion. If the severity of the injury is too great, the neuron will undergo apoptosis or cell death. However, if the cell body remains intact, chromatolysis may reverse, and the axon may regenerate with the formation of a growth cone. Schwann cells that proliferate around the endoneurial tube or basal lamina tube in the distal stump form bands of Büngner, which help guide the sprouting axon for regeneration. Human axon growth rates can reach 2 mm/day in small nerves and 5 mm/day in large nerves (112).

Epidemiology

Obstetric brachial plexus palsy has an estimated incidence of 0.2 to 5 per 1000 live births, and some studies report that the incidence in the United States is decreasing (153; 128; 14; 56; 44; 57; 167; 85). It was previously believed that 80% to 95% of all injuries are mild and most neonates recover in the first 2 months; however, evidence shows that the spontaneous recovery rate is 60% and some children suffer permanent impairment (77; 128). Erb palsy, which involves the upper trunk (C5-C6), occurs in about 60% of brachial palsy injuries, making it the most common type of brachial plexus injury. An additional 20% to 30% of injuries are the more extensive form of Erb palsy involving C7, and 10% to 20% have total or pan-plexus injuries involving C5-T1. Klumpke palsy, which is an isolated lower root injury involving C8-T1, is a rare entity with conflicting data on its incidence (64).

Erb-Duchenne C5-C6 palsy, occasionally bilateral and complicated by phrenic nerve injury, is the most frequent form of obstetric brachial plexus palsy after a breech birth (162). The more extensive form of Erb-Duchenne palsy (ie, C5-C7, rather than C5-C6) and pan-plexus palsy (ie, C5-T1) are particularly frequent after vaginal delivery with complicated cephalic presentations (162).

Risk factors. Suggested risk factors for obstetric brachial plexus injuries include shoulder dystocia, macrosomia (birth weight > 4 kg), maternal diabetes mellitus, small maternal stature (ie, producing cephalopelvic disproportion), maternal obesity, excessive maternal weight gain in pregnancy, high maternal parity (ie, 6 or more), prolonged pregnancy (postmaturity) or prematurity, prolonged second stage of labor, induction of labor, epidural anesthesia, secondary arrest of dilatation, persistent fetal malposition, instrument-assisted deliveries (ie, vacuum extraction and forceps delivery), downward traction of the fetal head, and vaginal breech extraction (25; 26; 153; 105; 72; 75; 83; 107; 143; 14; 44; 55; 160; 116; 167; 85; 174; 12; 50). The strongest risk factors for obstetric brachial plexus palsy are shoulder dystocia, macrosomia (especially infant birthweight of 4400 gm or more), and vaginal breech delivery (107; 01; 52; 116; 02; 57; 11; 163; 50). Risk of obstetric brachial plexus palsy increases progressively with increasing fetal size, with a 2.5-fold increased risk for 4001 to 4500 g neonates and a 21.0-fold increased risk for neonates greater than 4500 g, compared with the risk for infants of normal size (ie, 2501-4000 g) (105; 107).

Risk factors for a permanent injury with obstetric brachial plexus palsy include high maternal body mass index, shoulder dystocia, fractured humerus, and fetal asphyxia (14; 50). Fracture of the clavicle in vaginal deliveries is significantly more frequent with transient brachial plexus injuries, possibly reflecting a protective effect (14). Because intrapartum peak forces applied by the clinician are significantly lower in routine deliveries than difficult deliveries, infants born following routine deliveries are more likely to develop Erb palsy and ultimately good recovery, whereas those born following difficult deliveries are more likely to develop total palsy and have poor functional recovery (52).

Among 566 births with shoulder dystocia, brachial plexus injury was observed in 88 (16%), and permanent sequelae were detected in 12 (2%) (50). Maneuvers other than McRobert's (advanced maneuvers) were used more often, and clavicle fracture was seen more often in the group with plexus injury. Brachial plexus injury was observed 4.7 times more often in infants who were delivered with advanced maneuvers and 3.6 times more often in infants with clavicle fractures at birth.

In breech presentations, obstetrical brachial plexus palsy mainly results from “faulty performance of the manoeuvres that are needed to deliver the shoulders,” and there is a high frequency of root avulsions in breech deliveries of low birthweight infants (156; 26).

Shoulder dystocia. Shoulder dystocia, reported in 0.2% to 3.3% of all births, occurs due to the discrepancy between fetal shoulder size and the maternal pelvic inlet (60). The reported incidence of obstetric brachial plexus palsy after shoulder dystocia varies widely from 4% to 40% (44). Shoulder dystocia is anticipated to cause anterior shoulder involvement, which would produce a higher frequency of right obstetric brachial plexus palsies because the left occipito-anterior presentation is most common; nevertheless, posterior shoulder involvement is frequently seen (82).

Shoulder dystocia is defined by the American College of Obstetrics and Gynecology (ACOG) as any birth that requires obstetric maneuvers to deliver the fetal shoulders, and it is the highest known risk factor for brachial plexus injury (152; 56). Shoulder dystocia is often encountered unexpectedly--either when downward traction of the fetal head fails to deliver the shoulders, if there is extensive fetal vertex molding in prolonged labor, or if the fetus shows the “turtle sign” (19). Turtle sign refers to the retraction of the presenting chin into the maternal perineum due to bilateral shoulder dystocia. The most reliable predictor for shoulder dystocia is a previous episode of shoulder dystocia (42). Although shoulder dystocia is more common in macrosomic babies (ie, birthweight more than 4000 gm), fetal macrosomia is not a reliable predictor of shoulder dystocia (117).

Ultrasound examination is an unreliable mechanism in detecting fetal weight, with only 62% to 66% accuracy in detecting weight within 10% of the actual fetal weight (29).

ACOG recommends delivery via Cesarean section for babies weighing more than 5000 gm but does not have any current delivery recommendations for prevention of shoulder dystocia (38). For every 14 fetuses with an expected birth weight of more than 5000 gm delivered by cesarean section, one case of brachial plexus birth palsy can be prevented (39).

There are several maneuvers that can be implemented during vaginal delivery to relieve shoulder dystocia and, thus, prevent brachial plexus injury. The McRoberts maneuver refers to the positioning of flexed maternal thighs towards the maternal chest to slide the maternal pubic bone over the fetal anterior shoulder (84). This maneuver, coupled with suprapubic pressure, resolved 25% of cases of shoulder dystocia in one study (96). If the McRoberts maneuver fails to relieve the shoulder dystocia, rotational forces like the Woods’ corkscrew maneuver and Rubin maneuver can be applied. The Woods corkscrew maneuver applies force on the anterior surface of the posterior shoulder whereas the Rubin maneuver applies force on the posterior shoulder. The Rubin maneuver had a success rate of 66% and a birth injury rate of 14%. The Woods corkscrew maneuver had a success rate of 72% and birth injury rate of 9.5%. It is important to note that these maneuvers are usually performed after, or with, the McRoberts maneuver complicating the reporting of success and birth injury rates (78). The Zavanelli maneuver, or cephalic replacement, pushes the fetal head back into the mother so that the obstetrician can attempt a C-section and is rarely performed in the United States; consequently, there are very few reliable data in the literature to assess its rate of success or birth injury (96).

In a retrospective review of 46 children with neonatal brachial plexus palsy and shoulder dystocia, the incidence of brachial plexus palsy persistence was significantly higher at 2 years of age when more than three maneuvers were used or when the duration of the impacted shoulder lasted more than 120 seconds (43).

A strategy of prompt identification of shoulder dystocia accompanied by cessation of axial fetal head traction can decrease the risk of brachial plexus strain, injury, or tear, whereas performance of exact obstetrical maneuvers allowed delivery of fetal shoulders without permanent obstetrics brachial palsy or cerebral morbidity (69).

Closer attention to optimal management of shoulder dystocia has improved birth outcomes: in Sweden, obstetric brachial plexus palsy in vaginally delivered infants in a cephalic presentation at birth decreased during the period 1997–2019 despite an increase in important risk factors, including shoulder dystocia (108).

Cases with no known risk factors. Most cases of neonatal brachial plexus injuries have no known risk factors, and a significant proportion are now thought to occur in utero (90; 46; 82; 72; 61; 83; 14; 44; 55; 116). In a case in which the brachial plexus injury involved the posterior shoulder following a spontaneous delivery without forceps or manual rotation, with delivery effected using only the McRoberts maneuver, the authors hypothesized that maternal expulsive forces combined with lodging of the posterior shoulder on the sacral promontory caused the injury (72). Neonatal brachial plexus palsy can occur after cesarean section, sometimes in association with uterine pathology (eg, bicornuate uterus or uterine fibroids) (46; 61; 05; 116).

In addition, electrophysiological studies have demonstrated evidence of denervation on the day of birth, which is not attributable to a birth-related injury (90). Possible mechanisms of intrauterine brachial plexus injury include the endogenous propulsive forces of labor, intrauterine maladaptation or failure of the shoulders to rotate, impaction of the posterior shoulder behind the sacral promontory, and uterine anomalies (eg, fibroids, an intrauterine septum, or a bicornuate uterus) (46; 72; 44). Indeed, fetal macrosomia is a risk factor for obstetric brachial plexus palsy regardless of whether the delivery is vaginal or by cesarean section (105).

Temporal trends. The epidemiology of obstetric brachial plexus palsy in the United States may be changing over time due to population-level changes in obstetric care, particularly a significant increase in the rate of cesarean delivery (37); indeed, the rate of obstetric brachial plexus palsy declined from 1.7 to 0.9 cases per 1000 live births in the interval from 1997 to 2012, in parallel with increasing rates of cesarean delivery. Cesarean section is associated with a decreased risk of obstetric brachial plexus palsy but does not eliminate the risk completely (46; 61; 107; 143). In particular, for singleton pregnancies with breech presentation or fetal macrosomia, the frequency of neonatal brachial plexus palsy can be reduced with planned cesarean delivery (105; 75). However, this is controversial because a policy of elective cesarean section for fetal macrosomia would require 148 to 258 cesarean sections to prevent a single persistent injury, and avoidance of operative vaginal delivery would require 50 to 99 cesarean sections per injury prevented (91). Indeed, a decision-analysis study to estimate the potential effectiveness and monetary costs of a policy of elective cesarean delivery for fetal macrosomia diagnosed by ultrasound concluded that for the 97% of pregnant women who are not diabetic, a policy of elective cesarean delivery for ultrasonographically diagnosed fetal macrosomia is “medically and economically unsound” (133). The best approach in pregnancies complicated by diabetes and fetal macrosomia is less clear (133).

Differential diagnosis

The physical findings of brachial plexus palsy are unique, so it is difficult to mistake it for other diagnoses. However, these findings could be considered in the differential diagnosis of cerebral injury, cervical spine injury, trauma, and dislocation of the upper extremity as well as an inherited autosomal-dominant brachial plexopathy called hereditary neuralgic amyotrophy in affected families (94; 121; 73; 103; 80; 17; 102). Many of these have brachial plexus palsy as a finding in addition to other characteristics. Also, a case report of an arachnoid cyst that communicated with the dura of the C7 nerve root showed the patient presented with symptoms of obstetric-induced brachial plexus palsy. When the lesion was resected, the patient eventually recovered function (109).

Diagnostic workup

Neonatal brachial plexus palsies are typically diagnosed during physical examination. A thorough neurologic examination involves assessing for the presence of the Moro reflex and the asymmetric tonic neck reflex. The diagnosis of brachial plexus palsy is supported by the absence of reflexes that induce elbow flexion, wrist extension, and digit extension. Additionally, the presence of Horner syndrome may indicate lower root injury and generally conveys a worse prognosis for functional recovery (51). The presence of crepitus, gross deformities, or lower extremity involvement may suggest alternative diagnoses like humeral or clavicular fractures and cerebral hypoxia.

There are three main diagnostic modalities in working up brachial plexus palsies: plain radiographs, MRI, and CT myelography. Because most cases resolve spontaneously, these tests are usually performed after 3 months of age. Plain radiographs of the cervical spine, shoulder, clavicle, elbow, and hand help rule out fractures, dislocations, subluxation, septic arthritis, dysplasia, and other abnormal anatomy (40; 03). CT myelography offers the best visualization of rootlets at each level of the spinal cord and is, therefore, optimal for its use for detecting pseudomeningoceles that are associated with nerve root avulsions (165). MRIs have the advantage of being noninvasive, don’t involve exposure to radiation, and can allow for visualization of the spinal cord and brachial plexus, but this modality is less sensitive than CT myelography in detecting nerve root avulsions (13; 173). A preliminary study suggests that 3-D proton-density MRI can evaluate spinal nerve roots in infants with suspected brachial plexopathy, without the need for radiation, contrast agents, or sedation; if confirmed, this may allow for earlier determination of the severity of injury based on serial clinical assessments (18). A systematic review concluded that MRI is the most sensitive and specific diagnostic modality for identifying preganglionic nerve injuries (eg, pseudomeningoceles and rootlet avulsion, the latter of which has the poorest prognosis in this patient population and often dictates the need for surgical intervention) (65).

Of note, EMG and nerve conduction studies are not routinely performed in the assessment of brachial palsy injuries because these tests provide limited predictive value for the presence of specific root damage. However, nerve conduction studies are used to monitor operative progress by establishing a baseline (140). A meta-analysis, however, noted the overall poor quality of available studies but, nevertheless, suggested that the most methodologically sound studies of the prognostic value of early electrodiagnosis in neonatal brachial plexus palsy support the use of electrodiagnosis, at standardized timeframes, as a key prognostic modality for complementing clinical judgment and neuroimaging (166); this conclusion was challenged, however, and at present the general utility of electrodiagnosis for neonatal brachial plexus palsies is unclear (130; 168).

Management

Neonatal brachial plexus injuries generally require multidisciplinary management (151; 47). Early surgical referral may improve outcomes in patients unlikely to recover sufficiently with conservative management (151). Outcomes are better than the natural history of the condition in appropriately selected patients with surgical management (151). New treatment paradigms and prediction algorithms may facilitate appropriate surgical case selection (151; 172; 177).

The main goal of the surgery in infants with Erb palsy is to restore shoulder and biceps muscle function. In palsy involving C7 nerve roots, reinnervation of the triceps is important. In global palsy, the primary focus is on hand reinnervation and grasp function, followed by elbow flexion, shoulder function, and finally, elbow, wrist, and finger extension (99; 101; 159). Even primary C5-8 brachial plexus reconstruction can provide restoration of elbow flexion and provide most affected patients a sensitive and functional hand, although secondary surgery to improve shoulder and wrist function is often necessary (98).

Primary nerve repair or nerve transfer procedures using microsurgery have now replaced muscle and tendon transfer as primary treatment modality, starting as early as 3 months of age but no later than 6 months of age. Secondary procedures 12 to 18 months after the primary treatment include tendon transfer and contracture release (36). Patients with chronic lesions who cannot undergo or have not responded to reconstruction undergo secondary reconstruction. These procedures consist of arthrodesis, muscle releases, neurovascular tissue/muscle or tendon transfers, or tenodesis.

Surgical exploration. For a patient with Erb palsy, a supraclavicular exposure is sufficient to expose the C5-C6 roots. An incision is made through the skin and platysma behind the sternocleidomastoid’s posterior border to the clavicle. Then dissection through the omohyoid is performed to expose the clavicle with division of the subclavius muscle and the periosteum of the clavicle (120). One then identifies the pectoral nerve branching off the anterior division of the upper trunk to preserve it. The upper trunk and spinal nerves that lie between the anterior and middle scalene muscles are exposed by reflecting aside the fat pad in the posterior triangle of the neck (123; 15). Care must be taken to identify the phrenic nerve (anteriorly located on the anterior scalene muscle) and the spinal accessory nerve, which may be aided with direct electrical stimulation (123; 120). Commonly, the trunks are surrounded by fibrotic tissue due to the initial injury (123). Exploration may disclose avulsed ganglia, neuroma in continuity, a ruptured brachial plexus, or a pseudomeningocele.

Although there are no randomized trials comparing surgical reconstruction versus conservative treatment in infants with obstetrical brachial plexus palsy, some authorities have proposed that nerve reconstruction is indicated “when the result of nerve surgery is assumedly better than the expected natural recovery, [and] spontaneous recovery is absent or severely delayed” (127). Nerve grafts are harvested from sensory nerves such as the sural nerve, the medial brachial nerves, and antebrachial cutaneous nerves (123). Other sources include parts of the plexus where regeneration probably won’t succeed, like the medial cord, ulnar nerve, the C7 spinal nerve, and the spinal accessory nerve; however, the presence of a pseudomeningocele precludes the use of the nerve for grafting (123; 114).

Neurotization utilizes nerve transfers to connect an uninjured neighbor nerve to the distal portion of an injured nerve, which is useful in avulsion injuries. Best candidate donor nerves are spinal accessory, intercostal, medial pectoral, thoracodorsal, long thoracic, and subscapular nerves; however, in infants, the efficacy is unknown for the use of the long thoracic, pectoral, thoracodorsal, and subscapularis nerves (100).

Bahm and colleagues found in their practice that examination of each root sample on the distal stump by a neuropathologist intraoperatively from major trunks or connections with doubtful quality was helpful in guiding the surgeon in evaluating the quality of the proximal and distal stumps for grafting. The characteristics used to judge the quality of the root are the fascicular pattern (meaning the number and arrangement of the fascicles) and the presence of fibrosis in the peri- or epineurium, the presence of Büngner bands, and the level of remyelination and number of ganglion cells (15). A retrospective review of the outcomes of 96 patients who underwent either primary (less than 3 months of age) or secondary surgical intervention for neonatal brachial plexus palsy found that there were significant improvements in shoulder function. Reconstruction of both axillary and suprascapular nerves yielded improved outcomes of shoulder abduction and external rotation, whereas the rerouting of latissimus dorsi or teres major tendons and lengthening of the extra-articular tendons significantly improved global shoulder function (158).

Neurolysis. Neurolysis involves the release of the nerves from adhesions and inflammation. Some studies suggest that neurolysis is an inferior technique compared to resection of the neuroma and nerve grafting methods (92; 97). However, other studies suggest that neurolysis may be beneficial in cases that only involve the upper and middle trunks of the brachial plexus rather than the total plexus (34; 31; 48; 67). Chuang and colleagues advocate neurolysis should be done to determine the extent of scarring and the severity of the nerve lesion. Less severe lesions would require only neurolysis as treatment where significant scarring warrants resection of the neuroma and nerve grafting (32). Laurent and Lee proposed that neurolysis should not be used when intraoperative electrophysiological recordings show greater than 50% drop in the amplitude of the muscle action potential; rather, neuroma resection is indicated (95).

Resection of neuroma in continuity. Another surgical treatment is total resection of the neuroma in continuity with nerve graft interposition rather than neurolysis. One concern is that resection of a neuroma in continuity would diminish motor function as a result of a loss of nerve fibers that cross the neuroma; however, aggressive resection has not been found to result in significant motor loss (27). As stated earlier, some surgeons rely on electrodiagnostic recordings to guide their approach to the repair whereas others’ standard of care uses the resection of the neuroma with nerve grafting alone (64). Once resection of the neuroma has taken place, nerve grafts are used to bridge proximal and distal nerve stumps to guide growing axons using usually autologous sural nerve grafts (100).

Cable grafting. Cable grafting utilizes sutures or glue to join nerve strands in order to produce a graft with the same diameter as the recipient nerve. This technique has not been extensively used in obstetric brachial plexus palsy (134).

Nerve transfer. Nerve transfer procedures involve coapting a nerve from outside (extraplexal) or inside (intraplexal) of the brachial plexus to a denervated brachial plexus nerve (114). This procedure is becoming more commonly used and is advantageous because only one interface is used as compared to the nerve graft where one has to connect two stumps (70). ‘‘Terminal nerve transfers’’ refers to the complete transection of the terminal portion of a donor nerve whereas “end to side nerve transfers” utilizes fascicles of the donor nerve and preserves the terminal portion of the donor nerve (114). Common donor nerves include the spinal accessory, medial pectoral nerves, intercostal nerves, contralateral C7, hypoglossal, and ulnar nerve fascicles (114; 70; 100). Recipient nerves may include the terminal branches of the axillary, radial, median, and musculocutaneous nerve as well as the suprascapular nerve (114). In the past, nerve transfers were used to improve rotator cuff and bicep function, but now studies are looking at elbow flexion and hand function (70). Transfer of an ulnar fascicle to the biceps branch of the musculocutaneous nerve (Oberlin transfer) provides greater early recovery of forearm supination compared with nerve grafting, with equivalent elbow flexion recovery (28).

Muscle transfer. Free muscle transportation is useful to restore elbow flexion and motor function of the fingers and wrist to attempt to restore prehension or grasping (41; 169). Previously, donor muscles used for reconstruction were the latissimus dorsi, gracilis and rectus femoris muscles. However, the best donor muscle is the gracilis muscle because the others are not as successful for improvement of finger function (41; 141). Neurotization of the free muscle transfer includes the use the spinal accessory nerve to the suprascapular nerve and the third to sixth intercostal nerves to the musculocutaneous nerve or the median nerve (41; 32). Also, some studies have demonstrated successful use of the contralateral C7 nerve root to restore extensor digitorum communis function (30; 169).

Botulinum toxin: Botulinum toxin type A may be used off-label as an adjuvant to physical therapy and surgery in moderate to severe obstetric brachial plexus palsy (58); ultrasound-guided injection may increase effectiveness and reduce adverse effects (58).