Introduction

The brachial plexus is the network of nerves most commonly formed by the ventral rami of the spinal nerves C5 to T1, which provide movement and sensation to the entire upper extremity. In some instances, C4 (22% of the population) and T2 (1% of the population) provide contributions to the brachial plexus, which are termed prefixed and postfixed cords, respectively. The brachial plexus is divided into the following segments: roots, trunks, divisions, cords, and terminal branches. A mnemonic such as Randy Travis Drinks Cold Beer, can help one to remember the order of the various components of the brachial plexus from proximal to distal. The ventral rami of the spinal nerves C5 to T1 that give rise to the plexus are called as the roots. The C5 and C6 roots unite to form the upper trunk, the C7 nerve root continues to become the middle trunk, and the C8 and T1 nerve roots join to form the lower trunk. Each of the three trunks separates into anterior and posterior divisions. The anterior divisions of the upper and middle trunks combine to form the lateral cord, while the anterior division of the lower trunk forms the medial cord. The posterior divisions of all three cords connect to form the posterior cord. The cords give rise to the terminal branches, which form the peripheral nerves of the upper extremity. More specifically, the ulnar nerve arises from the medial cord, the musculocutaneous nerve arises from the lateral cord, the median nerve arises from a combination of the medial and lateral cords, and the radial and axillary nerves arise from the posterior cord. There are numerous other branches at the various levels of the brachial plexus ( Fig. 11.1 ).

Anatomical image of the brachial plexus.

Courtesy of Joshua M. Abzug, MD.

Brachial Plexus Birth Palsy: History and Etiology

Brachial plexus birth palsy (BPBP) was first reported by William Smellie in 1764. However, at that time it was popularly accepted that the injury to the upper extremity in a newborn was congenital in nature. Over a century later, in 1872, it was confirmed by Duchenne de Boulogne that these injuries to the newborns’ upper extremities were not congenital in nature, rather, the result of a traumatic birth process, as Smellie had previously asserted; coining the term obstetrical paralysis. Later in 1877, Erb described injury localized to the upper trunk (C5–C6), now called as Erb’s palsy, which accounts for 60% of reported brachial plexus birth palsy injuries. In 1885, Klumpke reported an isolated injury to the lower trunk (C8 and T1), now called as Klumpke’s palsy, which in the literature is reported as the rarest form of injury, accounting for less than 2% of the reported obstetrical brachial plexus birth palsies.

The widely accepted etiology of BPBP is traction to the brachial plexus during the delivery process, resulting in a peripheral neuropathy with subsequent paresis or paralysis of the upper extremity musculature. Injury to the upper trunk in isolation is most common, however, in approximately 20%–30% of all reported cases of BPBP the middle trunk or C7 root is affected in conjunction with the upper trunk (C5–C6). This injury to C5–C7 is called as an extended Erb’s palsy. A total or global brachial plexus palsy is the result of injury to the brachial plexus that affects all of the nerve root levels (C5-T1) at some point along the brachial plexus, and carries the worst prognosis.

Infants that sustain BPBPs will present with weakness or paralysis of the muscles served by the injured nerve roots. In general terms, when the nerves originating from the upper trunk are injured, infants will demonstrate limitations in shoulder abduction, external rotation, elbow flexion, supination, and wrist extension. Classically, this presentation of upper extremity shoulder internal rotation, with elbow extension, forearm protonation, and wrist and digit flexion, is called as the “waiter’s tip” position. In extended Erb’s injuries, additional deficits in shoulder internal rotation, protonation and digit extension are often present, as well as potential ulnar drift. Global plexus injuries result in flaccid paralysis of the upper extremity, while Klumpke’s paralysis results in an upper extremity with paralysis of hand function.

Risk Factors

Although extensive research has revealed explicit risk factors for BPBP that will subsequently be discussed, it is important to note that in many cases of BPBP, known risk factors are not always present. Risk factors associated with BPBP can be related to the infant, the infant’s mother, or the actual process of labor and delivery. Risk factors include the following: shoulder dystocia, fetal macrosomia (>4 kg), multiparity, instrument-assisted delivery, maternal gestational diabetes, previous pregnancies resulting in BPBP, maternal obesity and/or excessive maternal weight gain, advanced maternal age (>35 years old), maternal pelvic anatomy anomalies, use of an epidural, induction of labor, prolonged second-stage of labor, hypotonia and intrauterine torticollis. ( Table 11.1 ) Of these risk factors, shoulder dystocia, macrosomia, and instrument-assisted delivery have been found to increase the risk of BPBP by presenting a 100×, 14×, and 9× greater risk, respectively. Shoulder dystocia occurs during a vertex delivery when the infant’s anterior shoulder becomes lodged on the mother’s pubic symphysis, widening the ipsilateral head–shoulder angle. Alternatively, the posterior shoulder can become lodged on the sacral promontory. It has been reasoned that fetal distress may lead to hypotonia making the brachial plexus more susceptible to injury during the delivery. Of note, cesarean section as a means of delivery does not eliminate the potential for BPBPs, but it does reduce the risk.

Incidence and Prognosis

According to a review of the literature on the epidemiology of BPBP, data varies significantly with respect to incidence, with rates as low as 0.19/1000 live births, to as high as 5.1/1000 live births. In a recent epidemiologic study of the Kids’ Inpatient Database, a decreasing trend in BPBP was observed between 1997 and 2012, with observed incidences of 1.7 per 1000 live births in 1997 to 0.9 per 1000 live births in 2012. The lack of consistency in the data has been attributed to variations in obstetric care, the average birth weight of infants, and reporting measures according to the region of the world from where the data are being obtained.

Reports on the prognosis of BPBP are also incongruent. Previously in the literature, it was consistently reported that BPBP is transient in nature, with 75%–95% of all injuries being classified as “mild” resulting in full spontaneous recovery within the first and second months of life; specifically, when the C5 and C6 nerve roots are the site of initial injury. More recently, the research of Foad and Hoeskma et al. estimates full spontaneous recovery rates in only approximately 66% of the BPBP population. For the remaining percentage of the population, where recovery is incomplete, conservative management through occupational and physical therapy interventions to address the residual impairments may not be sufficient, and surgical intervention may be required. Akel et al. (2013) reported that even with conservative management of the injury, more than 15% of patients have permanent disability, or substantially diminished function.

A consistent prognostic indicator within the current literature is the return of function of the upper extremity against gravity within the first 2–3 months of life. It is agreed upon that such return of function leads to complete recovery within the first 1–2 years of life. Alternatively, when only partial recovery against gravity is acquired between months three and six, patients will experience long-standing and sometimes permanent loss in total range of motion and strength, decreased limb length and/or girth, as compared to the unaffected upper extremity, and glenohumeral dysplasia, leading to functional impairment. The delay in against-gravity recovery is directly proportional to the long-term risk of incomplete recovery and functional impairments. As there are no finite, known clinical indicators relative to the extent of initial injury and specific prognoses, physicians and healthcare team members are cautioned when answering questions about prognosis around the time of injury.

Nerve Anatomy and Recovery

Attempts to predict recovery require knowledge of the type of nerve lesion sustained and the level or severity of the injury. The peripheral nervous system contains autonomic, sensory, and motor neurons. Each peripheral nerve is made up of three main layers, described from the innermost to outermost layer, they are the nerve fiber or axon covered by the endoneurium and myelin sheath, the nerve bundle (funiculis) or fascicle covered by the perineurium, and the nerve trunk covered by the epineurium. Injuries can occur at each of these layers within the peripheral nerve, and with differing levels of severity. In 1943, Herbert Seddon proposed that further attention needed to be placed on classifications of nerve injuries. Seddon therefore established a classification of three types of nerve injuries that lead to loss of function: neurapraxia (stretch), axonotmesis (partial tearing), and neurotmesis (rupture); listed in order of increasing severity. Later in 1951, Sydney Sunderland further expanded these classifications to include 5 degrees of nerve injury: Sunderland I (neurapraxia), Sunderland II–IV (axonotmesis), and Sunderland V (neurotmesis). These classifications are still utilized today. It is important to note that an avulsion injury can also occur, in which the nerve root is pulled out of the spinal cord.

Although each category of nerve injury carries its unique complications and clinical presentation, as the degree/classification of the injury increases in severity, the probability of recovery decreases proportionately. Sunderland I/Seddon neurapraxia is a stretch without disrupting nerve continuity. This type of injury may present clinically with decreased strength and sensation; however, autonomic function typically remains intact. As there is not permanent damage to the axons, recovery typically occurs spontaneously within 3 months. Sunderland II–IV/Seddon axonotmesis is characterized by a partial tearing of the nerve in which the axon is affected; however, the Schwann cell basal lamina and endoneurium remain intact, as well as the epineurium and nerve trunk itself. Although spontaneous recovery is possible at this level of injury, recovery time is longer due to Wallerian degeneration, followed by axon regeneration, which occurs at a rate of 1–8 mm/day. In Sunderland III injuries, axonal regeneration can occur; however, it is complicated by scarring to the endoneurium, thereby slowing the recovery process. Conversely, in Sunderland IV injuries, the scarring to the endoneurium is severe to the point where it obstructs axon regeneration. In this instance, recovery is not anticipated without surgical intervention to remove the scar tissue and a reanastomosis of the nerve segments. Sunderland V/Seddon neurotmesis results in complete postganglionic transection of the nerve. Lastly, one can sustain a preganglionic avulsion of the nerve root from the spinal cord. This level of injury carries the poorest prognosis with the likelihood that muscle function and/or sensation will not be restored without surgical intervention. Although surgical techniques may be employed in attempts to graft across a postganglionic tear, direct surgical repair of a preganglionic avulsion injury is not possible. In 1989, Mackinnon and Dellon described a sixth degree of injury, the neuroma incontinuity. This type of injury is characterized by varying degrees and patterns of injury to the fascicles, with a resultant mixed pattern of recovery.

Due to the initial similarity in clinical presentation of differing nerve lesions, recovery and extent of the injury cannot be determined immediately following birth. It is reasoned that should an infant not regain near complete recovery within the first weeks of life, anticipated recovery time ranges from several months to absence of full recovery, as more than a neurapraxia injury has occurred.

Clinical examination can provide insight into the level(s) of nerve root injury by looking at muscle function. Such identification will aid in predicting recovery and consideration of treatment options. In 1987, Narakas developed a classification tool that groups BPBP into four separate categories (I–IV), based upon the location of muscle weakness/paralysis, with the corresponding nerve roots, and likely outcome. ( Tables 11.2 and 11.3 )

Assessment

The therapist’s first contact with the patient and their family is ideally during the hospital admission at the time of birth, with a referral made to a brachial plexus injury clinic or specialist following discharge. When consulted to evaluate an infant with recorded shoulder dystocia or possible BPBP as an inpatient therapist, before the evaluation being initiated, radiographs need to be obtained to assess for the presence of a clavicle or humerus fracture if there is any tenderness to palpation or crepitus present. A fracture may be present on the ipsilateral or contralateral side of a BPBP. Additionally, a chest radiograph to assess for a raised hemidiaphragm may also be warranted. Should the imaging be positive for any of these three items, the treatment and caregiver education will differ from when these associated findings are not present. Regardless of the patient’s point of entry into therapy, the therapist should be familiar with the brachial plexus injury providers within the immediate geographical area as these infants and children will require specialized assessment and follow-up. Multidisciplinary teams involved in the care of this population typically include a compliment of pediatric neurologists, neurosurgeons, orthopedic surgeons, physical medicine and rehabilitation physicians, physical and occupational therapists, social workers, or any combination of these providers.

Although there exist different developmental milestones to consider when evaluating a newborn with a BPBP versus an older child, the basic tenets of the evaluation remain the same. The skilled therapists’ evaluation will assist in classifying the injury and determining the extent of the injury. The evaluation should begin with an in-depth history. Pertinent information to obtain includes the mother’s pregnancy and labor course, the infant’s hospital course, the initial presentation of the involved upper extremity, the history of any recovery in the upper extremity to date (if any), and any involvement from rehabilitation services (occupational therapy/physical therapy). Specific to the mother’s pregnancy and labor, attention is paid to the mother’s age, weight gain during pregnancy, presence of maternal or gestational diabetes and whether or not the labor and delivery was complicated in any way, more specifically, if instrumentation was utilized (i.e., forceps or vacuum) or if the patient had shoulder dystocia. Ideally, one would note what if any maneuvers were utilized to relieve the shoulder dystocia. The infants’ hospital course should include the infant’s birth weight, APGAR scores, whether the normal hospital stay was prolonged for any particular medical reason, as well as any documented or noted impairments in vision, hearing, feeding, or respiration. Additional components of the evaluation include observation of the resting posture ( Fig. 11.2 ) and active movements of the infant ( Video 1 ), skin integrity, passive range of motion, muscle tone, presence or absence of age-appropriate reflexes and protective reactions, sensation, palpation for pain, deformity or muscle tightness, postural control, differential diagnoses/associated findings, and the patient’s overall disposition and its impact on the assessment.

Presentation of a BPBP patient with a resting posture of shoulder internal rotation.

Courtesy of Shriner’s Children’s Hospital, Philadelphia, PA.

Resting posture is examined to identify any asymmetries throughout the cervical spine, trunk, and extremities. Active movements are observed both against gravity, as well as in gravity-eliminated planes where the focus is on identifying unilateral weakness ( [CR] ) ( Fig. 11.3 ). Passive range is completed bilaterally, with the focus on identifying any unilateral limitations. It is important to describe the end-feels, whether the joint is hypermobile or hypomobile. Range should be assessed at the cervical spine, shoulder, elbow, wrist, and digits, inclusive of assessment of scapulohumeral rhythm. Upon initial assessment of an infant with a BPBP, if a passive range of motion limitation exists, a differential diagnosis must be considered. Muscle tone should be assessed for normalcy, hypertonicity, hypotonicity, or flaccidity throughout the body. For the infant population, the Moro, Asymmetrical Tonic Neck, Palmar Grasp, Placing, Arm Recoil, and Placing reflexes can be utilized to elicit active movement and observe for symmetry. In addition, tactile stimulation may elicit active movements in a newborn child ( Videos 1 and 2 ).

Clinical photograph of a child with BPBP on the right demonstrating active elbow extension against gravity, but no elbow flexion against gravity.

Courtesy of Joshua M. Abzug, MD.

Palpation during the clinical examination can be utilized to assess for clinical signs of pain that may be associated with an undiagnosed clavicle and/or humerus fracture, or it can identify muscle tightness. For example, the extremity can be passively placed into abduction and external rotation while assessing for tightness at the pectoralis major, latissimus dorsi, and teres major muscle groups. A significant portion of the population with upper trunk lesions will present at a few months of age with tightness of the internal rotators, often with limited active and passive external rotation ( Fig. 11.2 ). Palpation is also critical in assessing for posterior shoulder subluxation. Clinical indicators for the presence of posterior shoulder subluxation are either the lack of passive external rotation (estimated at −30 degrees to 5 degrees) on initial evaluation, or a loss of passive range at subsequent assessments. In conjunction with the assessment of external rotation for limited range, the posterior aspect of the shoulder should be palpated for what has been described as fullness, which is a result of humeral head displacement. Other clinical factors that raise concern for the potential of a posterior subluxation are asymmetrical soft tissue folds of the proximal aspect of the extremity and asymmetry at the axilla with a deep/concave presentation in the presence of subluxation.

At approximately 4 months old, assessment of the patient’s postural control can be conducted ( [CR] ). For postural control, the therapist is assessing the patient’s ability to interact with the environment, moving against gravity while maintaining the position of the cervical spine, trunk, and limbs. Deficits in posture are seen with asymmetry at rest, and atypical movement patterns. As shoulder flexion is limited in many children with BPBP, they utilize postural compensations to achieve their desired movement pattern. A classic compensation is extension or hyper extension of the trunk, with concurrent posterior pelvic tilt and ribcage elevation. Postural control develops in the first months of life in a cephalocaudal fashion. The initial experience of infant’s weight bearing from the prone position affects postural control in the shoulder, trunk, pelvis, and lower extremities. Infants with BPBP often are unable to bear weight symmetrically in the prone position, if at all. Missing this key developmental milestone will likely lead to postural control deficits in sitting and standing.

In older children, deep tendon reflexes for the biceps (C5, C6), triceps (C7), and brachioradialis (C6) are assessed. When considering sensation, the Narakas Sensory Grading System can be utilized. In this system, a rating of S0 is given when there is no reaction to painful stimuli; S1 when there is reaction to painful stimuli, but no reaction to touch; S2 when there is reaction to touch, but not light tough; and S3 when sensation appears to be normal. It is important to remember, however, that sensory feedback is not going to directly correlate to motor function.

Differential diagnoses for BPBP include clavicle and humeral fractures, spinal cord injury, and cerebral anoxia, and therefore assessment for each of these items is warranted. If there is a clavicle or humerus fracture, the upper extremity should be immobilized via a swathe or by pinning the infant’s sleeve to the chest of their shirt for a period of 2–3 weeks. It is important to note that clavicle and/or humerus fractures can mimic a BPBP (a pseudopalsy) or can coexist with a BPBP. Due to the nature of the BPBP injury, there may be associated findings outside of the upper extremity. As such, neck positioning should be assessed for the presence of torticollis or muscle imbalance resulting in head rotation preferences with or without lateral tilt. Additionally, the lower extremities should be assessed for atypical muscle tone due to the risk of fetal asphyxia or hypoxia in the presence of a difficult delivery. If the phrenic nerve is involved in the injury, the patient will present with a raised hemidiaphragm and potential feeding difficulties. Horner’s syndrome (ptosis, miosis, and anhydrosis) and facial palsies may be seen with lower trunk involvement. Both Horner’s syndrome and a hemidiaphragm paralysis have a higher association with preganglionic injuries.

There are several assessment tools that have been developed specifically for the BPBP population for assessing muscle function and ultimately nerve regeneration. These assessment tools are the Toronto Test Score, the Active Movement Scale (AMS), the modified Mallet Classification, Gilbert and Tassin Muscle Grading System, and the Medical Research Council Scale (MRC). The Toronto Test Score, AMS, and modified Mallet Classification have been proven reliable. In addition to using these tools, a baseline Narakas level should be recorded during the initial evaluation and each subsequent reevaluation.

The Toronto Test Score, developed by Michelow et al., scores abduction, elbow flexion, wrist extension, digit extension, and thumb extension, each on a scale of 0–2, with zero signifying no function, one equating to partial function and two as normal function, for a total possible score of 10. If by 3 months of life, the patient does not score greater than 3.5 on this tool, surgeons may deem this as an indication for primary nerve surgery. ( Table 11.4 )

Table 11.4

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