Brachial Plexus Palsy: Pathophysiology, Diagnosis, and Management

ABSTRACT: Brachial plexus injuries can be caused by trauma sustained during a difficult childbirth, and it affects approximately 1 to 2 children per 1000 live births. Erb’s palsy is caused by injury to the fifth (C5) and sixth cervical (C6) spinal nerves, whereas Klumpke’s palsy is caused by injury to the eighth cervical (C8) and first thoracic (T1) spinal nerves. With prompt treatment, up to 95% of patients can make a full recovery. Thus, making a prompt diagnosis is necessary for a good outcome. In this review, the pathophysiology and management of brachial plexus injuries are discussed, along with the clinical findings associated with both palsies, in an attempt to aid clinical diagnosis.

Brachial plexus injuries were first described and documented in the late 1700s by William Smellie, a Scottish obstetrician. It wasn’t until the late 1800s, however, that a French neurologist, Guillaume Duchenne, coined the term obstetric palsy and described the mechanism for brachial plexus injury.¹ 

ANATOMY 

The brachial plexus is a collection of nerves that control various functions—from sensations to movements—in the upper limbs. The plexus is divided into roots, trunks, divisions, cords, and branches (Figure 1). The roots of the brachial plexus are formed by spinal nerves C5 through T1 (Figure 2). At this level, the brachial plexus innervates rhomboids and levator scapulae (C4, C5 via the dorsal scapular nerve). 

In addition, the long thoracic (C5 through C7) and phrenic (C5) nerves innervate serratus anterior and diaphragm, respectively. The roots come together and form the superior (C5, 6), middle (C7), and inferior (C8, T1) trunks. The superior trunk innervates the subclavius, supraspinatus, and infraspinatus muscles, whereas the middle and inferior trunks continue—becoming the nerves that innervate the muscles discussed later.  

Following this, the trunks move laterally and cross the posterior triangle of the neck. While in the posterior triangle, the 3 trunks split into anterior and posterior divisions, each of which contain fibers from superior, middle, and inferior trunks (Figure 3).

Thereafter, the divisions enter the axillary region, where they become cords and are named relative to their position to the axillary artery: posterior, lateral, and medial cords. The posterior cord (C5 through C8 and T1) gives rise to the upper suprascapular, thoracodorsal, lower subscapular, axillary, and radial nerves. These nerves innervate subscapularis, latissimus dorsi, subscapularis, teres major, deltoid, teres minor, triceps brachii, supinator, brachioradialis, and extensor muscles. 

The lateral cord (C5 through C7) gives rise to the lateral pectoral, musculocutaneous, and lateral root of the median nerve. These nerves innervate pectoralis major/minor, coracobrachialis, brachialis, and biceps brachii, along with some of the fibers becoming the lateral cutaneous nerve of the forearm. 

The medial cord (C8 and T1) gives rise to medial pectoralis, medial portion of the median, medial cutaneous nerve of the arm/forearm, and the ulnar nerve. These nerves innervate pectoralis major/minor, add fibers to the median nerve, and are responsible for the flexor, thenar, lumbricals, and intrinsic hand muscles.² Brachial plexus palsy is an injury to these nerves resulting in loss of movement in the arm. Brachial plexus palsy is divided into Erb’s palsy and Klumpke’s palsy depending on the injured part of the brachial plexus.

EPIDEMIOLOGY

Overall, brachial plexus birth palsy (Erb’s and Klumpke’s) occurs in 2 per 1000 live births. Erb’s palsy affects 1 in 1000 newborns, whereas Klumpke’s palsy occurs in 0.8 to 1 per 1000 births. Brachial plexus palsy affects males and females with equal frequency, with African American being more predictive of injury.^3,4

PATHOLOGY/PATHOPHYSIOLOGY

Brachial plexus injuries occur when the infant’s shoulder becomes lodged behind the mother’s pubic bones during delivery. When the uterus contracts it causes pressure on the baby’s neck, which leads to stretching and injury of the brachial plexus. It is considered a medical emergency and can be fatal. 

Erb’s palsy is a brachial plexus birth injury of the superior trunk (C5 through C6), whereas Klumpke’s palsy is a birth injury of the posterior or medial cords (C8 through T1). Injuries to the plexus can be divided into 3 types: 

1. Neuropraxia—occurs due to stretching without tearing of the brachial plexus. This injury spares the axon. It is the most common type of brachial plexus injury, with a recovery of 90% to 100% of function within 3 to 4 months after treatment, and occurs without any wallerian degeneration occurring.⁵
2. Axonotmetic—in this type of injury, there is damage to both the axon and the myelin sheath leading to nerve degeneration distal to the site of injury. The epineurium and perineurium is often undamaged and recovery, which is usually not complete, takes longer in this type of injury (4 to 6 months).⁵ 
3. Neurometric—these injuries are the most severe and are associated with destruction of nerve and surrounding tissue, including the epineurium, perineurium, and endoneurium. The damage with this type of injury is mainly associated with the formation of a neuroma due to traction or laceration. This leads to wallerian degeneration, which is when scar tissue forms distal to the injury site due to the proximal end of the nerve trying to regenerate and approximate itself without supportive tissue. In this type, muscle atrophy starts to develop between 3 and 6 months after injury, and surgery is usually the only treatment option.⁵ 

CLINICAL PRESENTATION

Erb’s palsy typically presents with the infant displaying the waiter’s tip position, in which the arm is extended and adducted with a pronated forearm. Klumpke’s palsy typically presents with the infant displaying the claw hand. Upper extremity involvement could include the arm being held in a supinated position with flexion at the elbow and extension at the wrist.⁶ In addition, both palsies may present with respiratory depression. 

PHYSICAL EXAMINATION

Physical examination should include a complete neurological, musculoskeletal, and eye exam to properly evaluate brachial plexus injuries. It is important to assess the hand size and check if there is atrophy of pectoralis major because this helps decide whether the injury occurred prior to birth. It is also important to evaluate the neonate for facial nerve palsy, torticollis, cephalohematoma, clavicle/humeral fractures, paralysis of the diaphragm, and Putti’s sign (while shoulder is abducting, the medial edge of the scapula protrudes above the shoulder joint). In addition, there can be posterior subluxation of the humerous primarily due to the imbalance between the internal and external rotators.

Infants with nerve injury to the C5 through T1 roots, better known as complete palsy, present with limp arm and absence of movement as well as deep tendon reflexes. In cases of C5-T1 injury, it is important to perform a complete eye exam because Horner syndrome is often present. Horner syndrome would present with ptosis, anhidrosis, and miosis. This indicates there has been damage to the stellate ganglion, which is composed of the inferior cervical and first thoracic ganglions at the C7 vertebral level.⁷ In addition to lack of arm movement and Horner syndrome, patients with C5-T1 brachial injury also present with weakness of the intrinsic hand muscles and often have respiratory depression. 

MANAGEMENT

The following procedures may be done to diagnose brachial plexus palsy: electromyography (useful to decide if surgical intervention is necessary), nerve conduction studies or magnetic resonance imaging (to assess injury severity and presence of avulsion injury).⁷ X-rays may be needed to assess diaphragm paralysis due to phrenic nerve damage and fractures of the clavicle or humerus. Physical therapy is the mainstay of treatment for these palsies. The goal should be improvement in overall function of the upper extremity, and avoiding deformities and contractures. 

There are 2 surgical methods for treatment of more severe injuries; however, the timing for both are controversial. In neurolysis, scar tissue removal is done in an effort to preserve the underlying nerve fibers. The second method involves nerve grafting and a variety of these procedures are described.⁸ 

The sural nerve is generally the one chosen to be grafted in the area of injury. The tubulization procedure involves creating special tubes in the hopes that nerves will reconnect when autologous nerve transfer is not possible.⁷ If a child presents late, usually there are bony deformities and the only surgical treatments would be a release procedure or osteotomy.

PROGNOSIS

Overall, there is full recovery in 95.7% of patients with brachial plexus palsy. Improvement in the first few weeks of life indicates a good prognosis. However, complete recovery is unlikely if no improvement occurs in the first 2 weeks of life. Most newborns with brachial plexus palsy will likely grow into full functioning adults with little to no residual pathology.⁹

Carl Tabb II obtained his BS from the University of Michigan and is currently a fourth-year medical student at Michigan State University College of Human Medicine in East Lansing, Michigan, with an anticipated graduation date of May 2016. Tabb worked on this article with the guidance of Deepak Kamat, MD, PhD, who is a professor of pediatrics at Wayne State University in Detroit, Michigan.

REFERENCES

1. Duchenne GBA. De L’Electrisation Localise et de Son Application a La Pathologie et La Therapeutique. Paris, France: JB Balliere; 1872. 
2. Moore K, Daly AF, Agur AM. Clinically Oriented Anatomy. 6th ed. Baltimore, MD: Lippincott Williams and Wilkins; 2010. 
3. Gilbert WM, Nesbitt TS, Danielsen B. Associated factors in 1611 cases of brachial plexus injury. Obstet Gynecol. 1999;93(4):536-540. 
4. Weizsaecker K, Deaver JE, Cohen WR. Labour characteristics and neonatal Erb’s palsy. BJOG. 2007;114(8):1003-1009.
5. Eng GD, Binder H, Getson P, O’Donnell R. Obstetrical brachial plexus palsy (OBPP) outcome with conservative management. Muscle Nerve. 1996;19(7):884-891.
6. Glanze WD, Anderson KN, Anderson LE. Mosby’s Medical, Nursing, and Allied Health Dictionary. 6th ed. St. Louis, MO: Mosby; 1990.
7. Vredeveld JW, Blaauw G, Slooff BA, et al. The findings in paediatric obstetric brachial palsy differ from those in older patients: a suggested explanation. Dev Med Child Neurol. 2000;42(3):158-161.
8. Battiston B, Guena S, Ferrero M, Tos P. Nerve repair by means of tubulization: literature review and personal clinical experience comparing biological and synthetic conduits for sensory nerve repair. Microsurgery. 2005;25(4):258-267.
9. Russman B. Neonatal brachial plexus palsy. UpToDate. http://www.uptodate.com/contents/neonatal-brachial-plexus-palsy. Accessed April 15, 2015.