Brachial Plexus Injuries, Obstetrical Treatment & Management

Initial therapy involves protection of the joints and surrounding ligaments and tendons from stress.^[23] Physical therapy is used to maintain passive range of movement of the affected joints. In patients with obstetrical brachial plexus paralysis (OBPP), some believe that transcutaneous electrical stimulation is useful in waking up muscles that have been successfully reinnervated over a period of time.^[24] However, no scientific studies exist to support this conclusion. The authors do not use transcutaneous electrical stimulation in adults, although they endorse it in the older OBPP population.

Although variation exists in the recommended timing for surgery for young patients with brachial plexus paralysis (OBPP), the authors believe that if the infant does not show recovery of neurologic function by age 4 months, surgical intervention should be scheduled. Surgical reconstruction involves neurolysis, nerve grafting, and/or nerve transfer.^{[25, 26]}

If clinical or electrodiagnostic evidence of recovery is not present at 4 months, the authors believe that surgical exploration should be recommended. Most reports in the literature suggest that the lack of clinical evidence of elbow flexion by 3-4 months is an indication for surgery.

Fracture or dislocation is ruled out in preoperative evaluation at birth. Movements of the fingers, wrist, elbow, and shoulder are noted. Physical examination is obviously more difficult in the newborn, and clinical observation is especially important in this population. Chest radiographs are used to evaluate patients for phrenic nerve paralysis. Fluoroscopy of the diaphragm may be necessary. The MRC grading system (see Introduction, Clinical, above) can be used but is of limited use in young patients with brachial plexus paralysis (OBPP). Gilbert and Tassin have suggested an M0 to M3 grading system (see Introduction, Clinical, above). The Active Movement Scale (see Introduction, Clinical, above) developed by Clarke provides a reliable tool for assessing motor function in infants with OBPP.

Tricks for evaluating the infant's movement include offering them treats or toys. Sensory evaluation is difficult but includes evaluation of the infant's response to nonpainful touch stimulus and painful touch stimulus.

Technique

Loupe magnification, preferably 4.3, is used with a microscope for microneurosurgical repairs or grafts. Nerve coaptations are done with 9-0 microsuture so that there is no tension at the repair site. Marcaine is placed at the incision site for postoperative pain relief. A Jackson-Pratt drain is used.

An infraclavicular and supraclavicular surgical approach is recommended for reconstruction. The pectoralis major is divided at the tendinous insertion to expose the brachial plexus and then is reattached at the end of the procedure. The brachial plexus is explored and evaluated with intraoperative electrical stimulation. In some cases, following a neurolysis of the brachial plexus, a good muscle contraction is seen with electrical stimulation, and no further surgical intervention is needed. However, in more severe injuries, nerve transfers or nerve grafts are necessary. The sural nerve or the medial antebrachial cutaneous nerve can be used as a nerve graft for upper plexus injuries.

In patients with upper brachial plexus injuries, the entire upper plexus can be grafted or grafting can be combined with nerve transfer procedures. The upper plexus can be grafted to the suprascapular and axillary nerves. To provide a closer motor nerve to the injured muscle, a nerve transfer using a portion of the ulnar nerve (as described by Oberlin) can be used to reconstruct the musculocutaneous nerve to the biceps.^{[27, 28]} Mackinnon has described a modification of the Oberlin transfer to augment elbow strength and to provide increased elbow flexion strength by using a portion of the medial pectoral nerve and transferring it to the brachialis muscle.^[29]

In complete avulsion injuries, the distal accessory nerve and intercostal nerves can be transferred for reconstruction. Usually, at least one root can be used as a proximal source of nerves, and nerve grafts can be used to reconstruct shoulder function. The hierarchy of reconstruction is to address elbow flexion, shoulder function, and finally wrist and hand function. Therefore, in avulsion injuries, the intercostal nerves are transferred to the musculocutaneous nerve for elbow flexion, and the distal accessory nerve can be transferred to the suprascapular nerve.

The cross-chest reconstruction with C7 motor root from the normal brachial plexus transferred over to the injured side has been used in some infants with good success. By contrast, in adults, this procedure provides motor function on the injured side only, with movement from the noninjured side. Therefore, both extremities must be moved together for motor function of the injured extremity, making this nerve transfer extremely confusing for the patient. In patients with obstetrical brachial plexus paralysis (OBPP), spontaneous motor reeducation allows the infant to separate function on each side.

The bulky dressing is removed 2-3 days after surgery, and the drain is then removed. Infants are kept in a papooselike dressing for a month following surgery to allow the pectoralis major muscle to heal if it was detached from the humerus.

Physical therapy is initiated within a month of surgery to recover passive range of movement. Transcutaneous electrical muscle stimulation can be used; however, no scientific evidence indicates that it is efficacious in patients with brachial plexus injuries, and, therefore, in the authors' practice, electrical muscle stimulation is not used in patients with OBPP.

Initially, patients with obstetrical brachial plexus paralysis (OBPP) are monitored for wound management. Four weeks following surgery, patients are referred for therapy to regain active and passive range of motion of the extremity. Recovery of some motor function usually is evident approximately 6 months following surgery. However, patients continue to improve for 2-3 years following surgery. Secondary procedures, such as muscle transfers, tendon transfers, or shoulder releases, may also be necessary to maximize function.

Complications of surgery for obstetrical brachial plexus paralysis (OBPP) are similar to those of other surgeries and include infection, hematoma, seroma, and injury to other structures, including vascular structures. Unique to this surgery is the possibility of further inhibiting function by injuring components of the brachial plexus that are normal or recovering. In this patient population, injury to the phrenic nerve can result in devastating pulmonary compromise that could require urgent diaphragmatic plication. In theory, an intercostal motor branch or a nerve to the rectus muscle can be transferred to the distal end of the phrenic nerve, just above the diaphragm, to provide some reinnervation of the diaphragm.

The possibility of spontaneous recovery in patients with obstetrical brachial plexus paralysis (OBPP) is usually very good in most infants. Michelow et al evaluated the natural history of OBPP in 66 patients and reported that 92% of these infants recovered spontaneously.^[30] Shenaq et al reported a 95% spontaneous recovery rate in infants with OBPP and stated that patients without improvement of biceps, triceps, and deltoid muscle function within 3 months have poor functional recovery without operative intervention.^[21] Therefore, most infants who present with OBPP recover spontaneously due to the relatively minor degree of nerve injury. However, in patients in whom nerve injury is more severe and spontaneous recovery is not probable, surgical intervention is instituted.

No randomized studies exist to compare surgical management with conservative management for obstetrical brachial plexus injuries. Eng et al did a retrospective chart review of clinical evaluation, electrodiagnosis, and functional outcome with conservative management of 186 patients with OBPP.^[31] They reported that most patients had an upper brachial plexus palsy; injury was mild in 63% of cases. Most patients did not change in their impairment status as determined by the authors. Because the authors did not indicate the follow-up period in these patients and because of the retrospective nature of the study, it is difficult to draw meaningful conclusions from this study.

Strombeck et al reported on the functional outcome in 247 children (5-year follow-up) with OBPP with and without surgical reconstruction.^[32] The children were assigned to 1 of 3 groups for evaluation, depending on the number of nerves injured, evidence of recovery in the biceps or deltoid muscle by age 6 months, and whether any nerve reconstructions had been performed, as follows:

• The early-recovery group included children who showed some muscle activity in the biceps or deltoid muscle by age 3 months.
• The nonoperated group included children who showed muscle recovery after age 3 months, who were too old for surgery (age >18 mo), whose parents declined surgery, and who dropped out of the study after the initial evaluation.
• The operated group included children who underwent surgical reconstruction for their brachial plexus palsy.

In this study, 129 children had C5-6 palsy. Of these, 106 had early recovery, 8 children had surgery, and 15 children had neither early recovery nor surgery. In the 85 children with C5-7 lesions, 29 had early recovery, 24 had surgery, and 32 had neither early recovery nor surgery. Stromberg et al concluded that in the C5-6 group, shoulder range of motion was significantly better in those children who had surgery, and no other significant differences existed between those children who had surgery and those who did not have surgery. In the patients with the most root avulsions, a correlation existed between decreased hand function and increased root avulsions. Because of bias in patient selection for surgery, it is difficult to extrapolate these results for decision-making regarding conservative or surgical management for the child with OBPP.

Brown et al evaluated 16 children with prior OBPP using somatosensory and electromyography.^[33] They concluded that the persistent functional loss may be due to impaired motor unit activation.

Historically comparing conservative management with surgical intervention is difficult because of the likelihood that those patients who have surgery have the most severe nerve injury. Therefore, comparisons between surgical and conservative management would likely compare patients with more severe nerve injuries who had surgery with patients with less severe nerve injuries who did not have surgery.^[34] However, regardless of the management instituted, patients with lower brachial plexus avulsion injuries rarely recover hand function.^{[35, 36]}

Secondary surgical procedures involving tendon and muscle transfers and releases are available to patients with functional limitations.^{[37, 38]} Limited shoulder function can be enhanced at a later age with procedures to release the subscapularis muscle or transfer the teres major and latissimus dorsi muscles.^[39] Recovery of elbow flexion can be augmented at a later date with muscle or tendon transfers.

Controversy exists in the United States over the timing of surgical reconstruction for obstetrical brachial plexus paralysis (OBPP). Many reports in the literature suggest that surgical intervention should be left until the child is aged 4 months and the surgeon does not excise portions of the brachial plexus that are demonstrating clinical or electrical evidence of recovery. Some surgeons suggest that surgeries performed on patients younger than 4 months with aggressive excision and reconstruction of the brachial plexus are decreasing function for brachial plexus elements that have potential to recover spontaneously. Note that the vast majority of infants with OBPP recover well without surgery.

Donor-related nerve grafts (allografts) have been used in a small number of patients for brachial plexus reconstruction following traumatic nerve injuries. The authors' group has performed a number of nerve allografts in older children and young adults with otherwise unreconstructable injuries. The authors do not recommend the widespread use of nerve allotransplantation for patients with OBPP until the side effects of immunosuppression and transplantation have been resolved. With success in studies in inducing tolerance to the nerve allograft, the side effects of immunosuppression and transplantation would be eliminated. The authors' group has shown the benefits of FK506 (an immunosuppression transplantation drug) to enhance nerve regeneration. Use of this drug at an immunosuppressive subtherapeutic dose or use of an FK506 analogue may be considered to enhance nerve regeneration.