Depending on the severity of the injury can either resolve on its own over a period or leave residual weakness.
Relevant Anatomy and Pathophysiology
Brachial plexus is formed of nerves roots from C5-T1 vertebra.
As these roots come out, C5 and C6 join to form the upper trunk, C7 travels alone as the middle trunk, and C8-T1 join as the lower trunk.
Further, each trunk divides into anterior and posterior divisions and various divisions rejoin to form cords, which then subdivide further into branches that supply the muscles of the arm.
Depending on the severity of the injury, the nerve injury can be neuropraxia, axonotmesis and neurotmesis
- Neuropraxia denotes temporary loss of motor and sensory function due to blockage of nerve conduction. These lesions generally are reversible within 6-8 weeks and do not leave sequelae.
- Axonotmesis means disruption of the myelin sheath and the axon, leading to degeneration of the axon distal to the injury. The connective tissue across the lesion remains intact. These injuries improve gradually over 4-6 months.
- Neurotmesis means destruction of axon, myelin and supporting structures across a nerve. As the proximal end of the nerve attempts to regenerate without this supportive connective tissue, a neuroma may form. The improvement is variable.
An incidence of 0.8 -1.2 cases per 1000 birth has been reported. No sex predilection has been reported.
Causes of Erb’s Palsy
Conventionally, birth injuries during the delivery process had been held responsible for Erb’s palsy and other brachial plexus injuries presenting immediately after birth but recent observations and studies have suggested it to be also either due to stretching in utero or during the descent of the fetus. The occurrence of shoulder dystocia has been related with 18.3-32% increase in risk.
As brachial plexus injuries are found more in babies with greater birth weight, and these babies are more associated with shoulder dystocia, it has been recommended when the estimated birth weight exceeded 4.5 kg option of a cesarean section should be discussed with mothers.
- Large birth weight
- Breech presentation
- Maternal diabetes
- Prolonged labor
- Traction on the head or assisted delivery
- Intrauterine torticollis
- Shoulder dystocia
Less common risk factors are a neoplasm, intrauterine compression, humeral osteomyelitis, hemangioma and exostosis of the first rib.
Presentation of Erb’s Palsy
Usually, the baby is born after a difficult delivery and after delivery, the affected arm hangs loosely at the child’s side. Respiratory depression may indicate an associated phrenic nerve palsy.
The infant with an Erb’s palsy keeps the arm adducted, internally rotated, with the elbow extended, the forearm pronated, the wrist flexed, and the hand in a fist [Waiter tip deformity]. Sometimes, the limb is flaccid.
In patients where the injury, the affected arm may develop more slowly than the healthy arm and may be much smaller and may have impaired muscular, nervous and circulatory development leading to reduced healing ability of the skin, incomplete sensory perception.
Lab studies generally are not necessary.
High-resolution MRI is the best imaging study for this palsy. It shows the extent of trauma, including pseudomeningocele, and the presence of roots in the neural foramen.
Plain radiographs can be helpful in diagnosing hemidiaphragm paralysis from phrenic nerve involvement and fractures of the clavicle or humerus. X-rays also help to rule out posterior shoulder dislocation.
Electrodiagnostic studies like electromyography at 2-3 weeks can indicate on the severity and timing of the injury.
Some babies recover on their own. However, some may require intervention. Physical therapy forms an important part of both the conservative and operative treatment.
This begins as early as possible. Initially, the arm is fixed across the child’s chest by pinning of clothing to provide more comfort. Gentle range of motion exercises. While dressing, the arm should be gently dealt to avoid further traction on the limb.
Wrist extension splint may help to reduce the risk of contractures.
Physical activity that involves both the limbs should be encouraged. Some examples of these activities are swimming, basketball playing etc.
Apart from this, activities for strengthening and promotion of sensory awareness should be done, and provision of instructions for home activities. Overall goals should focus on minimizing bony deformities and joint contractures associated with brachial plexus palsy, while optimizing functional outcomes.
Hand and wrist splints, elbow extension splints, dynamic elbow flexion, and supinator splints help to reduce contractures and prevent further deformity. In older children with persistent disability, self-stretching and strengthening exercises should be done.
Without physical therapy, there is a risk of progressive contractures, posterior shoulder dislocation, and agnosia of the affected limb.
The three most common surgical treatments for Erb’s Palsy are
- Nerve transplants
- Subscapularis releases
- Latissimus Dorsi tendon transfers.
Subscapularis release aims at lengthening of subscapularis muscle by a Z shaped cut. It can be carried out at almost any age.
Latissimus Dorsi Tendon Transfers
Latissimus Dorsi is cut half horizontally, pulled in part and attached the outside of the biceps. This procedure provides external rotation.
Surgeries commonly performed are neurolysis and excision of the neuroma and nerve graft reconstruction.
Surgical intervention is said to be most effective when performed in patients as young as 2 months.
Neurolysis is the removal of scar tissue around the nerve. This is done if there is enough conduction across the neuroma. Otherwise, excision of the neuroma and nerve grafting is done.
Nerve transfer (neurotization) is required in cases where there is not a sufficient donor nerve, as in cases of avulsion.
Tubulization uses a conduit to help guide the 2 ends of a nerve together.
Late surgery for BPP most often involves tendon transfers and/or osteotomies.
The treatment aims at improving the flexibility and active movement of the shoulder.
Tendon transfers often are delayed until age 2-4 years to allow for motor recovery. The most common transfers include triceps to biceps and pectoralis major or latissimus dorsi to biceps.
A humeral external rotation osteotomy can be considered in older children for functional improvement.
Neuromuscular electrical stimulation and botulinum toxin A therapy have been suggested bu the role is not clear.
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