Approach

The diagnosis of brachial plexus birth injury (BPBI) is usually straightforward. After ruling out pseudoparalysis from another cause, confirm the diagnosis with history and physical exam, focusing on the neurologic exam.

History and general physical exam

A history of a pregnancy complicated by maternal or gestational diabetes or maternal obesity is often encountered.[15][19]​​ These factors may play a role in fetal macrosomia. The child will often be large (>4000 g) at the time of delivery.[19]​​[25][26]​​ The second stage of labor may have been abnormal, and the delivery may have been complicated by shoulder dystocia.[2][19][24][20]​​​[32][33]​​​​​ Assistive techniques, such as vacuum or forceps, may have been used to facilitate the delivery, and the child may have required resuscitation after delivery.[15][19][35]​​ The mother may have a history of shoulder dystocia in previous deliveries.[23]

Immediately after birth, the family typically notes decreased or absent movement of the infant's affected arm. An interval of normal movement of the arm followed by paralysis should raise suspicion that the infant does not have a BPBI. Children with severe BPBI related to nerve root avulsion from the spinal cord may show features of Horner syndrome (pupil miosis, partial ptosis, enophthalmos, and anhydrosis) on the same side as the brachial plexus injury.[43] Tachypnea, respiratory distress, feeding difficulties, and failure to thrive may indicate the presence of diaphragmatic paralysis due to phrenic nerve injury.[44][45]

A thorough examination of the child is warranted. A head-to-toe evaluation will reveal any other medical problems. A general examination of the newborn includes evaluation of the following.

  • Head: for cephalohematoma, plagiocephaly, and torticollis

  • Face: for evidence of Horner syndrome or facial nerve palsy

  • Spine: for evidence of deformity (scoliosis or kyphosis) or fracture (swelling, crepitance, or discontinuity)

  • Lower extremities: for evidence of hip dysplasia, foot deformity, or lack of spontaneous normal movement

  • Upper extremities: for posture, deformity, and spontaneous movements.

Musculoskeletal and postural examination

The normal neonatal position of the upper extremity is in shoulder abduction and external rotation, elbow flexion, forearm supination, wrist extension, and finger and thumb flexion. A child affected by Erb palsy will either hold their arm at the side, with the shoulder internally rotated, elbow extended, forearm pronated, wrist flexed, and fingers flexed (waiter tip position), and/or show decreased motion of the arm.[46][47][48][49]​ Patients with global injuries may have flaccid paralysis of the entire limb.

Careful palpation of the affected extremity may reveal crepitance, typically of the clavicle or humerus (indicating fracture). Medial clavicle fractures in particular may be associated with BPBI.[50][51]​ A fracture requires immobilization for up to 2 to 3 weeks, from which point recovery is expected. There should be no contracture present at any joint in any direction in the neonatal period. Lack of full range of motion on gentle passive movement should lead to a search for evidence of dislocation (rare) and consideration of alternative diagnoses.[52]

Neurologic examination

Having ruled out a fracture or dislocation, the child is observed for spontaneous movements of the arm. Any movement deficits at the following joints are noted, and compared with the unaffected side.

  • The shoulder: observed for flexion, internal and external rotation, and abduction

  • The elbow: observed for flexion and extension

  • The forearm: observed for pronation and supination

  • The wrist and fingers: observed for flexion and extension.

Stroking the skin along the desired muscle can sometimes stimulate the child to contract the underlying muscle and produce movement if the muscle remains innervated. As the newborn cannot cooperate with instructions, patience may be required to allow time for the child to move the arm freely in every direction possible.

Children who have been hypoxic after delivery and required resuscitation may show signs of central nervous system dysfunction or hypoxic ischemic encephalopathy, such as hyperreflexia, persistent primitive reflexes, abnormal muscle tone, or abnormal body posture.

Quantification of upper-extremity function and prognosis

Several scoring systems have been devised to evaluate and monitor patients with BPBI. The most commonly used and validated systems to define injured nerves and monitor recovery following injury or after surgical repair are as follows.

Toronto test score[53]

  • Defines the injured area in relation to 5 observed movements of the hand and elbow

  • Does not assess shoulder function

  • Graded on a scale of 0 (no motion) to 2 (normal full motion).The scores are summed can sum up to a maximum of 10 points for the 5 movements assessed. Lower scores indicate patients who may benefit from nerve repair surgery.

Active movement scale[48][54]

  • Consists of observation of movements of multiple joints and muscle groups, including shoulder function

  • More global than the Toronto test score

  • Tests 15 different active upper-extremity movements without gravity and against gravity, and scores each on a scale of 0 to 7.

Mallet scale[55]

  • Evaluates shoulder function in older patients (ages approximately 3 years and above) who can cooperate with instructions

  • Uses a grading scale of 1 (no movement) to 5 (normal motion; symmetric to the unaffected, contralateral side) for each of the 5 voluntary movements tested

  • A modified Mallet classification has been described, adding an additional internal rotation position to assess midline function.[56]

Medical Research Council (MRC) motor scale[57]

  • Commonly used to evaluate muscle strength, but use in babies is controversial as they cannot follow instructions

  • Uses a grading scale of 0 (no muscle contraction) to 5 (full active movement against gravity with full resistance).

Range of motion

Active and passive joint ranges of motion of affected joints are frequently recorded and tracked over time, particularly passive shoulder external rotation and passive elbow extension.

The Toronto test score and the active movement scale are more useful in newborns because they simply involve observation of natural movements of the extremity. The Mallet scale is used to follow shoulder function in older patients who can cooperate with instructions. Establishing a baseline score serves to guide treatment as recovery progresses and can be reassessed at each visit.[58]

Diagnostic investigations

Investigations are not usually necessary to diagnose Erb palsy or other types of BPBI. Ancillary studies may be useful for confirming the extent and location of injury and for surgical planning, although some argue that careful clinical assessment is sufficient for deciding which patients require surgery.[59][60]​​

Imaging

A routine radiograph of the affected extremity to include the chest may be useful to identify a clavicle fracture, a humeral fracture, or evidence of asymmetry of the diaphragm.[50][51]

Ultrasound may be used to diagnose a shoulder dislocation (rare) and diaphragmatic paralysis if suspected.[52][61][62]​ It has also proved to be useful for diagnosis of shoulder subluxation in older infants.[63] The advantages of using ultrasound are that there is no need for sedation and it is relatively inexpensive. However, it is operator-dependent and cannot evaluate the glenoid accurately.

A magnetic resonance imaging (MRI) or computed tomography (CT) scan may be performed if there is evidence of shoulder subluxation or for surgical planning. MRI is the best study to identify shoulder joint morphology as much of the infant's glenohumeral joint is cartilaginous at this age. The Waters classification system may be used to assess severity of glenoid deformity.[64][65]​​ Humeral head deformity and humeral retroversion can also be assessed with MRI.[66][67]​​ CT allows accurate evaluation of shoulder congruity and glenoid morphology in older children who have ossified glenohumeral joints.[68]​ However, CT scan also incurs radiation exposure. MRI and CT myelography of the cervical spine cannot accurately diagnose an injury but can identify pseudomeningoceles or rootlet avulsions associated with some nerve root avulsions.[69][70][71]​​ Imaging had a 70% sensitivity and 66% specificity for identification of nerve avulsions in one study.[59]

MRI and CT myelogram have comparable sensitivity and specificity. MRI may be preferred in younger children because it is noninvasive and does not require exposure to ionizing radiation or iodinated contrast.[22]​ Both require the patient to be sedated.

Electromyography (EMG) and nerve conduction studies

EMG/nerve conduction studies may be helpful to confirm the extent and location of injury and are sometimes obtained for surgical planning. In one study, EMG was less sensitive than imaging for detecting nerve root avulsions, but more specific - particularly for the lower nerve roots.[59]​ Due to the age and level of cooperation required by the newborn (birth to 4 weeks of age) or infant (4 weeks to 1 year of age), testing of voluntary activity is not possible, thereby decreasing the diagnostic capabilities of nerve testing.[72] However, pediatric reference values for neonatal EMG and nerve conduction studies are available to aid diagnosis.[60][73][74]​​[75]​​ Some reports suggest there may be value in their use in the first few days after birth for diagnosis and prediction of prognosis of BPBI.[72][75][76]

EMG/nerve conduction studies may provide overly optimistic results in infants. Birth injuries are frequently lower energy injuries occurring over a longer time period than traumatic brachial plexus injuries, which can result in stretch to the nerve prior to avulsion. This could result in loss of the sensory conduction that is typically maintained in nerve root avulsions from traumatic brachial plexus injuries. Additionally, disorganized axonal regeneration through a neuroma involving multiple nerve roots may result in electrodiagnostic signs of reinnervation that may not translate to functional recovery. Even the plasticity of the neonatal brain may not be able to reassign the disorganized regenerated neurons.[72]​ Thus, EMG/nerve conduction studies can be unreliable in accurately predicting recovery in infants with BPBI.

MRI and EMG/nerve conduction can be performed as part of the preoperative assessment regimen prior to planned surgical intervention (nerve repair) or in planning secondary reconstructive procedures to improve arm function at an older age.[70][72][77][78]

Emerging tests

While not yet routinely used, studies suggest the following may be useful:

  • Three-dimensional proton-density MRI: used for direct evaluation of the brachial plexus to determine if earlier surgical nerve reconstruction would be useful.[79][80]

  • Volumetric MRI and EMG assessment of rotator cuff muscles: evaluated in case series comparing the findings with global external rotation of the patient’s arm. Useful for recommending appropriate interventions to improve shoulder function.[78]

  • Ultrasound evaluation of the brachial plexus: used to define postganglionic injuries with neuroma formation, as well as to assess the shoulder for laxity in preoperative patients.[81] Findings correlate with MRI, but the lower plexus is difficult to image with ultrasound.[82]

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