Erb's Palsy

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Clinically Relevant Anatomy

Erb's palsy or Erb–Duchenne palsy is a paralysis of the arm caused by injury to the Brachial Plexus, specifically the upper brachial plexus. It is the most common birth related neuropraxia (about 48%).

It is a lesion of C5 & C6 nerve roots usually produced by widening of the head shoulder interval (in some cases C7 is involved as well).

Mechanism of Injury / Pathological Process

The most common cause of Erb's palsy is dystocia, an abnormal or difficult childbirth or labor. For example, it can occur if the infant's head and neck are pulled toward the side at the same time as the shoulders pass through the birth canal. The condition can also be caused by excessive pulling on the shoulders during a vertex presentation (head first delivery), or by pressure on the raised arms during a breech (feet first) delivery. Erb's palsy can also affect neonates affected by a clavicle fracture unrelated to dystocia.

A similar injury may be observed at any age following trauma to the head and shoulder, which cause the nerves of the plexus to violently stretch, with the upper trunk of the plexus sustaining the greatest injury. Injury may also occur as the result of direct violence, including gunshot wounds and traction on the arm, or attempting to diminish shoulder joint dislocation. The level of damage to the constituent nerves is related to the amount of paralysis.

Clinical Presentation

This type of injury produces a very characteristic sign called Waiter's tip deformity due to loss of the lateral rotators of the shoulder, arm flexors, and hand extensor muscles.  The position of the limb, under such conditions, is characteristic: the arm hangs by the side and is rotated medially; the forearm is extended and pronated. The arm cannot be raised from the side; all power of flexion of the elbow is lost, as is also supination of the forearm.

• Affected nerves are the axillary nerve, musculocutaneous, & suprascapular nerve
• Muscles most often paralyzed are supraspinatus and infraspinatus because the suprascapular nerve is fixed at the suprascapular notch (Erb's point)
• In more severely affected patients deltoid, biceps, brachialis, and subscapular is affected (C5 and C6)

• The arm cannot be raised, since deltoid (axillary nerve ) & spinati muscles (suprascapular nerve) are paralyzed
• Elbow flexion is weakened because of weakness in biceps & brachialis
• If roots are damaged above their junction, paralysis of rhomboids and serratus anterior is added, producing weakness in retraction and protraction of scapula
  

Diagnostic Procedures

Look for presence of cervical rib. In the report by Becker J, et al (2002), the authors noted that in a series of 42 infants found to have a cervical rib, 28 newborns had an Erb's palsy. They conclude that a cervical rib was a risk factor for an Erb's palsy.

Outcome Measures

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Management / Interventions

Some brachial plexus injuries may heal without treatment. Many children who are injured during birth improve or recover by 3 to 4 months of age, although it may take up to two years to recover. Fortunately, between 80% to 90% of children with such injuries will attain normal or near normal function.  Treatment for brachial plexus injuries includes physiotherapy and, in some cases, surgery.

Physiotherapy Management

During the first 6 months treatment is directed specifically at prevention of fixed deformities. Exercise therapy should be administered daily to maintain ROM and improve muscle strength. Parents must be taught to take an active role in maintaining ROM and keeping the functioning muscles fit.

• gentle range of motion exercise will prevent shoulder contractures;
• continuous splinting is contraindicated;
• however, positional splinting between exercises may be helpful;
• it is important to maintain full extension of fingers, hand, wrist, full pronation and supination of forearm, full extension of elbow, and full extension of elbow, and full abduction, extension, and external rotation of the shoulder;

Intervention Management

Indications for surgery is no clinical or EMG evidence of biceps function by 6 months. This represents 10% to 20% of children with obstetric palsies.

The three most common treatments for Erb's Palsy are: Nerve transplants (usually from the opposite leg), Sub Scapularis releases and Latissimus Dorsi Tendon Transfers.

Nerve transplants are usually performed on babies under the age of 9 months since the fast development of younger babies increases the effectiveness of the procedure. They are not usually carried out on patients older than this because when the procedure is done on older infants, more harm than good is done and can result in nerve damage in the area where the nerves were taken from. Scarring can vary from faint scars along the lines of the neck to full "T" shapes across the whole shoulder depending on the training of the surgeon and the nature of the transplant.

Subscapularis releases, however, are not time limited. Since it is merely cutting a "Z" shape into the subscapularis muscle to provide stretch within the arm, it can be carried out at almost any age and can be carried out repeatedly on the same arm; however, this will compromise the integrity of the muscle.

Latissimus Dorsi Tendon Transfers involve cutting the Latissimus Dorsi in half horizontally in order to 'pull' part of the muscle around and attach it to the outside of the biceps. This procedure provides external rotation with varying degrees of success. A side effect may be increased sensitivity of the part of the biceps where the muscle will now lie, since the Latissimus Dorsi has roughly twice the number of nerve endings per square inch of other muscles.

Differential Diagnosis

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Key Evidence

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Resources

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Case Studies

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Recent Related Research (from Pubmed)

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References

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