BRACHIAL PLEXUS PALSY
Birth brachial plexus injury occurs in between 1 and 2 per 1,000 live births in the United States. Babies with increased birth weights, multiparous mothers, and shoulder dystocia are at the highest risk for brachial plexus palsy (48,49).
The most widely described mechanism of action for this is lateral stretch, which is logical secondary to the location of the brachial plexus, the high correlation with shoulder dystocia, and the positioning of the mother and infant (49). It has been described that between 50% and 95% of these infants will recover spontaneously. The goal of treatment of brachial plexus injuries is maximizing arm and hand function. Goals are normalization of limb function, with optimization of nerve regeneration and mechanical increase of elbow flexion and shoulder stabilization. This can be achieved through aggressive rehabilitation and microsurgical intervention (48).For any nerve that is injured, classification makes evaluation and comparison clearer. The Seddon Classification of Nerve Injury is commonly used. Neurapraxia occurs with no lasting anatomical changes, with fibers preserved. This is exemplified by a football “stinger” injury. Complete resolution is expected. In axonotmesis, there is an interruption of neural continuity to some degree. There is an extremely variable level of deficit that is difficult to evaluate and predict the degree of recovery. Neurotmesis is the most severe injury, with total disruption of the elements of the nerve, and this will not recover. If it is preganglionic, or proximal to the dorsal root ganglion, it is called an avulsion. If it is postganglionic, or distal to the dorsal root ganglion, it is called a rupture (50). Both of these require surgical intervention for recovery.
There are also descriptors for the levels of brachial plexus palsy. Injury at C5-C6 is called Erb's palsy, sometimes called Erb-Duchenne palsy.
This is the most common level of involvement, present in approximately three-fourths of those with birth brachial plexus palsy. Involvement of C8-T1 is Klumpke's palsy. It is debated whether Klumpke's can occur in a birth brachial plexus injury, though it definitely occurs in other types of brachial plexus injury. The reason for this question is whether it is anatomically possible to have a C8-T1 lesion alone without involvement of C5-C7. It appears that if there is an anatomical variation—for example, a rib, tendon, bony, or other anomaly that leads to C8-T1 compromise—this can occur in a birth brachial plexus injury. Otherwise, it appears that it cannot. Therefore, if a child presents with a C8-T1 birth brachial plexus injury, it may be from anatomical anomaly, but there are two other options to consider. Most likely, it was initially a complete brachial plexus involvement but there was quick recovery of C5-C7. This is likely, since the upper cervical root levels are relatively protected anatomically so C8 and T1 may end up with the most severe injury. It is also possible that a spinal cord injury has been mistaken for brachial plexus palsy. All of these are important to consider during evaluation. There also may be a complete brachial plexus palsy, including C5-T1, with total motor and sensory loss. There also can be a variety of levels involved between upper plexus and total plexus palsy.Evaluation
Evaluation of patients with brachial plexus palsy includes clinical findings, electrodiagnosis, and MRI. There is debate about which of these is most effective. MRI is expensive and requires sedation to perform on infants. It has been found to correlate with surgical findings 70% of the time, electromyography 87% of the time, and clinical findings 60% of the time. The correlation was highest when all three of these were combined. MRI was effective only in those with C5, C6 root involvement (51).
Clinical exam consists of a history and physical examination.
The history includes the birth number of the child, the birth weight, and presence of maternal diabetes during the pregnancy, along with the size of previous infants and the birth size of the parents. The motor and sensory findings at birth, along with any change up to the time of evaluation, are important. The use of vacuum or forceps may be indicative of any difficulty with delivery. The most common association is shoulder dystocia. Other useful information is whether there were signs of bruising or other injury, or whether there was involvement of the contralateral arm or the legs at delivery.Physical examination begins with visualization of the arm to include the size and bulk. A cool temperature and blue color are sometimes noted. Sensory evaluation is critical to determine areas of involvement. Muscle stretch reflexes will be decreased or absent in the distribution of a brachial plexus injury. The primitive reflexes are also important. Since the upper plexus has more frequent involvement, the Moro reflex, which shows shoulder abduction and elbow flexion, is valuable in assessing those active movements. Torticollis is frequently seen, and usually this is with the face turned away from the involved arm. Range of motion is an important part of the evaluation since contractures are commonly seen in shoulder adduction and internal rotation, wrist flexion, forearm pronation, and even at the elbow into flexion commonly in later months and years.
A key goal of the electrodiagnostic evaluation is to find subclinical nerve and muscle responses. The study must be individualized, with studies performed that are pertinent to each individual’s examination. Sensory nerve conduction studies, motor nerve conduction studies, and electromyography are performed. Diagnostic evaluation should include nontraditional nerve conduction studies, and commonly not the classic median and ulnar nerves, due to frequent involvement of only the upper brachial plexus. Axillary, musculocutaneous, and radial nerves are among those useful for electrodiagnostic study.
Sensory nerve action potentials (SNAPs) are important, as these are most sensitive to axonal loss (52). The presence of SNAP responses in an insensate area is indicative of a preganglionic lesion, due to the location of the sensory cell bodies in the dorsal root ganglion. Electromyography (EMG) may show activation of motor unit potentials in muscles with no clinical motor activity. Electromyographic evaluation is reported of being of some benefit, but underestimating the severity of lesions (53). It has been recommended to be performed early in the first few days, then with a repeat evaluation after several months to more accurately identify cases where there is reinervation occur- ing and therefore having earlier determination of the need for surgical intervention (54).Plain x-rays may be useful. Other abnormalities may mimic a brachial plexus palsy, including a fracture of the clavicle or humerus. Osteomyelitis may also mimic this, and has actually been reported as inciting temporary brachial plexus palsy (55). Neurofibromatosis or other tumors may also cause it.
Treatment
Education is initiated when a family is first seen. Therapy should be started as soon as possible after diagnosis. Positioning instruction begins immediately, and range-of-motion exercises are generally initiated after two weeks. The wait is due to the fact that there is commonly noted to be pain with changing position of the shoulder for bathing or dressing in the first two weeks, so it appears that there is some tenderness after the initial brachial plexus injury, which is quickly resolved. It is also important to position the arm so that the baby will have maximal awareness of it. One way to accomplish this is with the use of a wrist rattle on the affected arm so that the baby’s attention can be drawn to that arm by sound or vision, because the weakness of that arm usually limits it from being moved in front of the face spontaneously. It is also recommended to have the family replicate movements with the affected arm that the baby spontaneously does with the unaffected arm, such as bringing the hand to the mouth.
It is important that the family realize that they need to perform the exercise program several times a day. It is also important not to have such aggressive range of motion in shoulder abduction or forearm supination that there is dislocation of the humeral head or radial head, respectively. Splinting is also commonly done by occupational therapy or physical therapy. Initially, there is frequently wrist drop, so splints may be made to provide optimal position of the wrist and fingers. Later on frequently there is an elbow contracture, so splinting is done to minimize that. Therapists also may do taping to help promote optimal positioning of the arm, particularly at the shoulder.Electrical stimulation is sometimes done for brachial plexus palsy, though this is frequently not tolerated at a very young age. Over time it does become accepted by many young children. Most commonly, it is performed with surface electrodes to increase muscle bulk by use of sufficient stimulation to get a local muscle twitch for approximately 20 minutes twice daily. It has been shown that continuous electrical stimulation to denervated muscles with implantable electrodes will lead to improved muscle outcome after nerve regeneration (56). This has not been widely utilized and is not currently available on the U.S. market.
It has been proposed that the adverse affects of prolonged denervation leave intramuscular axons deteriorated to such low numbers such that even with successful nerve regeneration, it is impossible to reinnervate enough muscle fibers for sufficient force (57). There are also proposals that low doses of brain-derived neurotrophic factor (BDNF) may protect against this decrease in those who have late nerve grafts, though high doses are inhibitory (58).
Complications
It is important to monitor for secondary complications. These commonly include muscle atrophy and joint contractures. The affected arm frequently is shorter and has decreased circumference as well.
Joints may become dislocated, and scapular winging is frequently seen. There may be torticollis, most commonly with the face turning away from the involved arm. General child development may be affected, including by lack of awareness of the arm. Similarly, body image may be affected. There can be ulcerations from trauma, particularly in insensate areas. Pain is infrequent after birth brachial plexus palsy but not after later trauma.Surgical Indications
Indications for timing of brachial plexus surgery for infants have been controversial. It has been shown that a longer time for recovery leads to a worse shoulder function and that those who regain elbow flexion after 6 months of age have worse function than those who regain it between 3 and 6 months (59). Those with recovery by 3 months have normal function. Those who had microsurgery at 6 months did better than those who spontaneously recovered elbow flexion at 5 months (60). Surgical intervention is commonly recommended for those having less-than-antigravity strength in elbow flexion at 6 months of age (61).
Later brachial plexus injuries are divided into supraclavicular and infraclavicular injuries, supraclavicular being 75% and infraclavicular 25%. Supraclavicular injuries are generally felt to be due to traction of the plexus (classically in a motorcycle crash), and these have a worse prognosis than infraclavicular injuries (62). There may be a fracture of the clavicle or cervical transverse process, and supraclavicular fossa swelling may be seen. Dorsal scapular nerve or long thoracic nerve injury may be present. Supraclavicular lesions may also be due to falls; large objects falling on a shoulder, such as a tree limb; skiing or climbing; or contact sports, including football (52). Other etiologies are backpacks that are too heavy, tumors and gunshot wounds, or lacerations or animal bites. Those who have ipsilateral Horner's syndrome and persistent pain have a worse prognosis (52).
Infraclavicular brachial plexus injuries are more commonly associated with fractures and dislocations about the shoulder or humerus, occurring more often in older adults. The posterior cord, axillary nerve, or musculocutaneous nerve are classically involved. Infraclavicular injuries are less severe and have better outcomes (63). Infraclavicular plexus injuries may also be due to falls, motor vehicle collision, or tumors (52). Gunshot wounds, stab wounds, and failed attempt at shoulder reductions may cause infraclavicular injuries as well (64). Brachial plexus palsy has been reported after axillary crutch use, anesthesia positioning (particularly with table tilt), and after bony fracture with malunion (65). For severe injuries later in life, recommendations are for surgical exploration and nerve grafting, most commonly at three to four months postinjury (64,66).
Surgery
Surgical interventions for brachial plexus palsy are varied. There may be electrical testing, including evoked potentials, and nerve conduction studies done to assess the nerves in the operating room to be as specific as possible with the procedures undertaken. Microsurgical repair yields results months later. Recovery is generally felt to proceed at the rate of approximately a millimeter a day or an inch a month. There is also felt to be more nerve growth factor available in younger beings so that both size and age have an impact in outcome. It is critical to have therapy postsurgery and to continue a faithful daily home program as well.
There are a variety of options for surgical procedures for brachial plexus injury. Neurosurgery may include neurolysis in which scar and fibrotic tissue are removed from nerve tissue. Direct nerve transfers have the advantage of quick recovery time due to short regeneration distance versus neurotization, which requires interposition of a nerve graft. The sural nerve and great auricular nerve are commonly used as donor nerve fibers for these grafts (67). More recently, end-to-side neurorraphy is performed for those who have some intact fibers for augmentation. The advantage of this is not requiring a sacrifice of any other nerves. Not uncommonly, synkinesis of newly innervated muscles with contraction of muscles innervated by the donor nerve may be seen, and is treated with therapy (68).
Some classic nerve procedures involve transfer from a functionally less important nerve to a distal denervated nerve. Common examples include taking intercostal nerves to the upper trunk or to the suprascapular nerve. Another classic surgery is the Oberlin procedure, which transfers one or several ulnar nerve fascicles to the musculotaneous nerve as it enters the biceps muscle (69). Transfer of the spinal accessory nerve to the suprascapular nerve is also commonly used for shoulder abduction. For approximately the last 10 years, contralateral C7 transfers have been performed both in adults and infants for those with multiple severe avulsions. This procedure has been shown to provide adequate elbow flexion as a result, and most patients have had only temporary sensory deficits on the ipsilateral C7 side (70). This procedure clearly illustrates the point that nerve grafts are not required to have their original source but can have function coming from a variety of intact neurological structures. This allows for greater flexibility and creativity in the surgeon performing the procedure, aiming for recovery of function.
Glenoid dysplasia with posterior shoulder subluxation is frequently a complication of children after birth brachial plexus palsy. It was commonly thought to be the result of a slowly progressive glenohumeral deformation due to muscle imbalance and possible physeal trauma, but it was found that posterior shoulder dislocation happened at a mean age of 6 months, with rapid loss of passive external rotation. There was no
correlation between the initial neurological deficit and the presence or absence of dislocation (71).
Many musculotendinous surgical procedures are performed for children with birth brachial plexus palsy. It has been shown that latissimus dorsi and teres major tendon transfer to the rotator cuff, along with musculotendinous lengthening, will provide improved shoulder function but no significant change in the bony position of the shoulder or humerus. This procedure does not decrease glenohumeral dysplasia (72).
With internal rotational contracture and glenohumeral joint deformity, along with significant abnormality of glenohumeral joint, a derotational osteotomy can result in improved shoulder function, along with improved internal rotation contracture (73).
Some children with birth brachial plexus palsy have been described to have arthroscopic release of shoulder deformity alone before 3 years, and for those over 3 years of age, arthroscopic release with latissimus dorsi transfer. They all show improved shoulder position, but they do have loss of internal rotation. Some of the children under 3 years do have a recurrence and require a second procedure with a latissimus dorsi transfer (74).
In adults, performing a glenohumeral arthrodesis, both in patients with upper plexus palsy with functional distal arm, as well as in those with total plexus palsy, has been shown to increase functional capabilities. The strength of the pectoralis major is a significant prognostic factor for outcome (75).
Performing wrist arthrodesis in adults with brachial plexus injury is done for improved function as well as pain relief. There will be limitations after having this procedure, and potential patients need to have full information in order to know what to expect prior to the procedure. There also remains some controversy of the ideal position to place the hand, which is generally placed in slight wrist extension and ulnar deviation in order to have the most powerful grip (65,76). A dramatic surgical procedure sometimes performed for children and adults with brachial plexus palsy is a free muscle transfer, most commonly performed with the gracilis muscle. The muscle is transferred with its vascular and nerve supply and attached to these in the arm. This procedure has been described as having reliable results for elbow flexion and wrist extension (65).
Pain
Pain has not been reported as a severe problem in birth brachial plexus injury, although with one study reporting biting of the limbs in less than 5% of the cases, it is possible that this is a manifestation of pain. Self=mutilation has been reported in youngsters after a birth brachial plexus injury. This study of 280 patients with a birth brachial plexus injury found that 11 of these children had self-mutilating behavior by biting or mouthing the affected arm. The age of onset was between 11 and 21 months, and the duration of the behavior was 4 to 7 months. This was more frequent in children who underwent surgery, with 6.8% of these children, and 1.4% of children who did not have surgery. It is unclear if this is due to surgery or the severity of the injury or a combination of these (77). It is also possible that this is a response to the unusual sensation of the recovering nerve, possibly a manifestation of what we see on examination as a Tinel's sign. It has been felt, however, that it is more likely biting with the resumption of nerve growth with sensation of tingling as there is recovery occurring, but this is not proven.
In those who have later traumatic or nontrau- matic brachial plexus injuries, pain can be a significant problem. It has been described most commonly with avulsions as severe burning and crushing pain most commonly in the hand. This may develop days to months after the injury and almost always within three months. It is most commonly resolved within several years, but approximately 20% of those with pain have severe, long-lasting disruptive pain (78). This can be treated with transcutaneous nerve stimulation classically from C3-T2. Medications, including antidepressants and anticonvulsant agents, have been affective. Topical treatments, including topical lidocaine 5% pain patches, are sometimes useful. Nerve surgery is commonly effective in resolving pain (79,80). The author has seen children with traumatic brachial plexus injuries and severe pain complaints prior to their nerve procedure wake up postopera- tively in the recovery room excited that the pain is gone. Amputation is not effective for resolving the pain (81).