Clinical presentation and considerations of neonatal brachial plexus palsy

Summary box

1

Neonatal brachial plexus palsy (NBPP) can be defined as a flaccid paresis of an upper extremity due to traumatic stretching of the brachial plexus, with the passive range of motion greater than the active.
2

The incidence of this condition varies somewhat with different factors including geography and baby size, but published values range from 0.10 to 5.1 cases per 1000 live births.
3

High birth weight, maternal diabetes during pregnancy, and shoulder dystocia are risk factors that have been associated with NBPP.
4

Various classification schemes have been reported for NBPP, each with its own merit.
5

The natural history of NBPP remains controversial: some investigators provide an encouraging view with over 80% occurrence of a favorable outcome or complete recovery whereas other authors provide a contrasting view with less than 50% good recovery with persisting disabilities.
6

Earlier recovery presages more favorable recovery.
7

A thorough maternal, obstetric, and perinatal history is crucial for providing relevant information that helps to direct the physical examination.
8

Neonates are unable to comply with voluntary maneuvers of the physical examination; therefore, different strategies must be used to assess NBPP patients, although the basic anatomical principles remain constant. Once the diagnosis is made, the parents / caretakers must be counseled appropriately.
9

Commonly used assessment scales in NBPP have primarily focused upon joint angles or muscle activation.
10

Global functional/disablement scales must be developed in the future for determining the optimal treatment and for evaluating treatment efficacy.

Introduction

Neonatal brachial plexus palsy (NBPP) can be defined as a flaccid paresis of an upper extremity due to traumatic stretching of the brachial plexus, with the passive range of motion greater than the active. The first description of NBPP was reported in the 18th century, and the noticeably shortened weak arm of Kaiser Wilhelm II of Germany has been attributed to NBPP. Approximately 1200 reports regarding NBPP exist in Medline from 1948 to the present, with nearly 100 of those reports within the last year. Increased interest in this condition has paralleled the improvement in outcomes that is attributed to increased recognition of this condition, improved care, and expanding research via interdisciplinary collaborations.

Incidence

The incidence of this condition varies based on geography of the reported regions and baby size, but published values range from 0.10 to 5.1 cases per 1000 live births. For instance, in the United States, analysis of data from the Kids’ Inpatient Database of over 11 million recorded births over 3 non-consecutive years yielded a mean +/− standard error of 1.51 +/− 0.02 cases per 1000 live births. Bilateral brachial plexus palsies occur in 8.3–23% of cases, primarily occurring with breech presentation. Advancements in modern neonatal and obstetric care, including more frequent use of Caesarian sections, were purported to decrease the incidence of NBPP, but recent published reports have not supported this idea.

Risk factors

NBPP has been associated with several maternal characteristics including advanced age (>35 yrs), pelvic anatomy high body mass indices (BMI), diabetes, and primiparity. Diabetes was present in 21% (vs 3–5% in the normal population) and hypertension was present in 17% (vs 2–3%) of women whose babies had NBPP (unpublished data). The most significant characteristic of the baby is high birth weight (>4 kg) although the relationship between increasing birth weight and increasing severity of NBPP remains uncertain. Approximately 14% of babies with NBPP had 5-minute Apgar scores of less than 7 (vs 3.8%); similarly, others report 49% of babies had an Apgar score of < or = to 7 at one minute. Labor and delivery factors include breech position, shoulder dystocia, forceps delivery, vacuum extraction, clavicle fracture, precipitous delivery, prolonged labor (second stage), and mode of delivery. These factors are addressed in detail in Chapter 5 .

Risk factors

Classification of clinical presentation

The most useful classification scheme was proposed by Gilbert and Tassin, refined by Narakas ( Table 4.1 ), and supported by Birch. The brachial plexus comprises the C5 through T1 nerve roots, and Group I represents the clinical findings resulting from nerve injury of C5 and C6, hallmarked by paresis of the deltoid and biceps but active function in limb extensors, wrist and hand. The clinical findings in Group II are related to injury of C5, C6 and C7. In addition to paresis of the deltoid and biceps, paresis of triceps and wrist extensors is also obvious; however, the long flexors and intrinsic muscles of the hand are relatively unaffected. Group III represents paresis of the entire arm consistent with injury of C5, C6, C7, C8, and T1. Group IV manifests as a paralyzed limb with the additional presence of Horner’s syndrome (ptosis, meiosis, anhydrosis) that implies injury to the all the nerve roots of the brachial plexus with a very severe proximal injury to the lower nerve roots. This Gilbert and Tassin/Narakas classification of NBPP was proposed following a prospective study of the natural history of the condition, discussed further in the next section. As such, when used between 2 and 4 weeks after birth (when neurapraxic lesions would be recovering), this system permits definition of the extent of injury and, more importantly, may guide prognosis.

Table 4.1

Gilbert and Tassin/Narakas classification scheme used for grading the severity of NBPP and for prognosis

Group	Affected nerve roots	Rate of full spontaneous recovery
I	C5, C6	~ 90%
II	C5, C6, C7	~ 65%
III	C5, C6, C7, C8, T1	< 50%
IV	C5, C6, C7, C8, T1 with Horner’s syndrome	~ 0%

Other classification schemes are based on the anatomy and physiology of nerve injury. Sunderland reported a physiologic scheme comprising four types of injuries in increasing severity (neurapraxia, neuroma, rupture, and avulsion) . He and others use an anatomical scheme comprising four categories based on anatomical location: upper, intermediate, lower and total plexus palsy. The concept of an upper plexus palsy involving C5, C6 and sometimes C7 was initially defined anatomically by Erb in 1874 after Duchenne in 1872 described four cases of complete paralysis involving loss of shoulder control and elbow flexion. The upper palsy, also called Erb’s palsy is the most common type of NBPP. Erb’s palsy is visually recognized by the stereotyped “waiter’s tip posture” with the arm adducted, shoulder internally rotated, wrist flexed, fingers extended. Intermediate palsy was described by Jolly in 1896 and Thomas in 1905, and this condition was thought to involve C7, C8 and Tl roots with the arms abducted, the elbows flexed, and the fingers/hands flaccid. Subsequently the muscles supplied by C8 and Tl spontaneously recovered to some extent but not those supplied by C7. A majority of these cases were bilateral and thought to be related to an obscure obstetric practice. Lower plexus palsy was described by Dejerine-Klumpke. This type of NBPP is rare but can be recognized by a flaccid hand in an otherwise active arm. Total plexus palsy is essentially the condition as described for Narakas Grades III and IV, and it is a devastating condition with total loss of function of the arm.

Natural history

The natural history of NBPP, around which the determination of optimal treatment revolves, remains the subject of speculation and is debated in many published reports. The evolution of NBPP is difficult to define because of the various combinations of lesions within the elements of the brachial plexus. Further difficulties include the interpretation of what constitutes recovery and the potential bias introduced by the referral patterns of reporting physicians, as many patients with Erb’s palsy recover spontaneously and are not referred to the specialists who publish most reports. With these caveats in mind, many authors provide an encouraging view of the natural history of NBPP with over 80% occurrence of a favorable outcome or complete recovery whereas other authors provide a contrasting view with less than 50% good recovery or persisting disabilities. Regardless of the neurologic recovery, functional recovery can yet be compromised by musculoskeletal defects, (e.g. contractures, joint subluxation) even with appropriate therapy management.

Most practitioners agree that as the extent and severity of NBPP increase, the potential for recovery decreases. A detailed prospective study by Gilbert and Tassin reported that 32% made a complete recovery. These patients were characterized by early rapid improvements in arm function with recovery of deltoid and biceps before 2 months of age. Forty-three percent made far less than full recovery. This group of patients was characterized by slow progress, with no evidence of biceps recovery until after 6 months of age. Their study led to the following prognostic conclusions: 90% of patients with Group I NBPP progressed to full spontaneous recovery if there were clinical signs of recovery before 2 months of age. Approximately 65% of patients with Group II palsy recovered fully, but the remainder had persisting defects in shoulder and elbow movement. The timing of recovery of this group of patients is delayed with clinical signs of recovery not evident until 3 to 6 months of age. For Group III patients, less than 50% recover fully spontaneously, with the majority of patients disabled by significant deficits of movement throughout the arm; in approximately 25% of patients, even wrist and finger extension remain functionally compromised. Patients with Group IV NBPP have little if any chance for a full spontaneous recovery; the stark reality is the expectation of a complete neurologic deficit of motor and sensory function in the affected arm. This classification/prognostication system attributed to Gilbert and Tassin, and Narakas remains a popular classification system not only for describing the severity of the pathology but also as a strong predictor of outcomes.

Similarly, most practitioners agree that early recovery is associated with favorable outcomes. The Collaborative Perinatal Study reported that 93% of patients who went on to full spontaneous recovery had done so by 4 months of age. Metaizeau et al. reported that patients who showed no signs of clinical improvement by 3 months did not recover function adequately, and those who continued not to show improvement by 6 months had essentially no chance of adequate functional recovery. Bennet and Harrold reported that their patients who recovered fully began to show clinical signs of improvement by 2 weeks of age. Yet other authors contend that all patients who recover satisfactorily achieve biceps and deltoid function by 3 months of age, and failure of recovery of anti-gravity power in the proximal muscle groups by 6 months of age essentially presages future moderate to severe weakness in the affected extremity. Note, however, that early elbow flexion alone is likely not a sufficient criterion to recommend for or against nerve repair reconstruction.

The predictors of recovery described above use simple clinical muscle assessments, but some authors have constructed paradigms based of more complicated statistical analyses of multiple independent clinical variables, but these models show only modest improvement in predicting recovery.

Assessment of the NBPP patient

Physical examination

The basic premises of the brachial plexus examination can be found in Chapter 3 . However, many of these maneuvers require voluntary cooperation of the patient that the neonates are unable to provide. Therefore, different strategies must be used to assess NBPP patients, although the basic anatomical principles remain constant. Once the diagnosis is made, the parents/caretakers must be counseled appropriately.

Prior to the physical examination, a thorough maternal, obstetric, and perinatal history (detailed in Chapter 12 ) is crucial for providing relevant information that helps to direct the physical examination. In the early days after birth, skeletal injuries/fractures should be detected by clinical and radiographic examination and treated accordingly after performing a standard neonatal medical examination. Spontaneous movements and normal reflexes should be observed, and deficits may indicate other associated disorders such as cerebral palsy or cortical dysplasia. Gentle handling of the neck and affected limb is appropriate, but no immobilization is recommended for NBPP that is not associated with skeletal injuries. Asymmetric expansion of the chest cavity and difficulty with oxygenation or feeding may indicate phrenic nerve palsy that can be confirmed with plain radiographs or ultrasound; this can be a dangerous condition resulting in early failure to thrive and should be addressed promptly. Observation of ptosis and meiosis are consistent with Horner’s syndrome that may indicate severe NBPP. Likewise, observation of classic postures (e.g. waiter’s tip) implies particular NBPP lesions.

Passive range of motion should be assessed. Generally contractures and joint subluxations do not develop for several months after birth, and early limitations of passive range of motion may indicate other musculoskeletal abnormalities. Active range of motion and muscle power can be difficult to assess, but engaging the neonate or child in play with toys or with irritating stimuli can be instructive: much can be gleaned from responses such as reaching out to grasp keys on a key ring, placing a cracker into the mouth, and assuming weight-bearing postures such as side sitting or crawling. As the baby grows, measurements of the circumference and length of the arm should be tracked as indicators of musculoskeletal dysfunction. Sensory function is similarly difficult to assess in detail, but a gestalt determination can be made by judging the baby’s response to particular stimuli (e.g. pinprick, pinch, heat or cold). Indications of chewing or biting of the arm / hand imply sensory alterations in the affected area. The presence of skin rashes in dermatomal distributions can also indicate sensory alterations.

Supplementing the physical examination with radiographic and electrodiagnostic findings is helpful to decide whether nerve repair reconstruction will be beneficial, and detailed discussions regarding these topics are beyond the scope of this chapter and are found in Chapter 7 , Chapter 8 , Chapter 9 .

Peri-operative/anesthetic assessment

In the patient who requires surgical nerve repair/reconstruction, a necessary pre-operative assessment regards the neonate’s tolerance for anesthesia. For relatively short procedures such as CT-myelogram, the anesthesiologist must assess the patient for intravenous access and control of oxygenation during prone positioning. After placement of standard American Society of Anesthesiologists (ASA) monitors, anesthesia is induced using oxygen, nitrous oxide, and sevofluorane. Intravenous access is acquired and secured without using the unaffected upper extremity, thereby reserving the vessels in the unaffected upper extremity for easier intravenous access on the day of surgery which may be as early as a few days after the radiographic study. Because the positioning of the patient changes during the procedure, control of the airway is imperative: the airway must be firmly secured with an appropriately sized cuffed endotracheal tube that can be quite small, then the patient is turned prone with all pressure points padded. At the end of the procedure the patient is extubated awake and discharged home from the post anesthesia care unit once the discharge criteria are met.

For the longer procedures including surgical nerve repair reconstruction, the anesthesiologist’s concerns increase because anesthetic complications are a leading cause of intraoperative morbidity. Pre-operative assessment of the neonate broadens to account for (i) the length of the procedure (over 6 hours), (ii) the availability of only one extremity for intravenous access and monitoring (both legs are prepared for potential harvesting of the sural nerves), (iii) the inability to use chemical paralytic agents because neurophysiological studies are used during surgery. Pre-operatively, midazolam 0.5 mg/kg orally can be used if separation anxiety is obvious. Anesthesia is then induced with oxygen, nitrous oxide, and sevoflurane. A peripheral intravenous catheter is placed and secured carefully in the unaffected upper extremity by the most experienced member of the anesthesia team (this is not a case for inexperienced personnel because there is only one limb to work with and very few veins that are readily accessible.) Propofol 1 mg/kg is given to facilitate endotracheal intubation and avoidance of muscle relaxants because of neurophysiologic assessment that will be used during surgery. The proper securing of the endotracheal tube to the contralateral side cannot be overemphasized. La Scala et al. found the most significant intraoperative complication in their series of patients undergoing brachial plexus surgery was inadvertent extubation that was resolved by suturing the endotracheal tube. An alternative solution is to insert and maintain the endotracheal tube slightly deeper during surgery. A radial arterial line is placed in the same limb as the intravenous catheter for hemodynamic monitoring as well as for regular intraoperative assessment of hematocrit and blood glucose.

Due to the need for neurophysiologic assessment during surgery, maintenance of anesthesia involves a combination of remifentanil (0.05-0.5 mcg/kg/min) and isoflurane (1 MAC or less titrated to effect). Dexmedetomidine 0.1-0.5 mcg/kg/hr can be added to supplement the anesthesia with minimal effect on monitoring while allowing a reduction in the amount of volatile agent being administered. Intraoperative neurophysiologic assessment may necessitate temporary muscle paralysis to reduce artifacts and can be achieved for approximately 30 minutes with cisatracurium (0.1 mg/kg). Perioperative fluid overload should be minimized by restricting intraoperative fluids to 4 ml/kg/hr. Assessment of fluid overload includes the monitoring of oxygen saturation to avoid pulmonary edema. The duration of surgery necessitates the tracking of blood glucose and hematocrit hourly. Continued postoperative vigilance of oxygen saturation and fluid status is necessary, especially if the baby is immobilized in a restrictive brace.

Assessment scales

Commonly used assessment scales in NBPP are used preoperatively but are more often used postoperatively to assess recovery. These scales primarily focus upon joint angles or muscle activation. For example, muscle power is generally expressed via the UK Medical Research Council Scale for muscle movement (MRC scale) ( Table 4.2 ). This provides structured grading of individual muscle groups, but does not provide any information about overall function of the limb or child. Because the MRC scale requires voluntary cooperation, it is difficult to apply in newborns. To overcome these difficulties in assessing the motor function in newborns, Curtis et al. proposed the Active Movement Scale (AMS) ( Table 4.3 ). In 2 complementary studies, the AMS was reported to be a reliable tool for evaluating infants with upper-extremity paresis and its inter-rater variability was independent of the rater experience. Moving more towards function of the whole limb, the Mallet scale provides a quantifiable assessment for shoulder function ( Figure 4.1 ). The inter-observer reliability of the Mallet score has been reported for the various movements, with the mean weighted kappa ranging from 0.53 for hand to mouth to 0.75 for abduction. The Mallet scale can be used in conjunction with Gilbert’s classification of shoulder paralysis ( Table 4.4 ) with some consistency reported between the two systems. The movements assessed in the Mallet scale use the shoulder and elbow. It primarily addresses upper plexus function after 3 years of age because it requires cooperation of the child. Likewise, limitations in passive range of motion, apraxia or neglect can alter the interpretation of the results. The interobserver reliability and internal consistency for the Mallet score and the AMS were reported as reliable instruments for addressing upper extremity function in patients with NBPP. For elbow function, an elbow recovery scale has been suggested by Gilbert and Raimondi ( Table 4.5 ). Similarly, Raimondi has proposed a hand evaluation scale ( Table 4.6 ) which has been used to assess hand function after nerve repair reconstruction and found to correlate with the pre-operative Gilbert and Tassin/Narakas grade.

Table 4.2

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