Erb’s palsy is a paralysis of the arm caused by injury to the upper group of the arm’s main nerves, specifically the severing of the upper trunk C5–C6 nerves.
The upper trunk C5–C6 nerves form part of the brachial plexus, comprising the ventral rami of spinal nerves C5–C8 and thoracic nerve T1.
These injuries arise most commonly from shoulder dystocia during a difficult birth.
The paralysis can resolve on its own over a period of months, or necessitate rehabilitative therapy, or require surgery.
Erb’s palsy can be partial or complete.
Damage to each nerve can range from bruising to tearing.
C5 is the most commonly involved root is C5 as this is mechanically the furthest point from the force of traction, therefore, the first/most affected.
It presents as a lower motor neuron syndrome associated with sensibility disturbance.
The most commonly involved nerves are the suprascapular nerve, musculocutaneous nerve, and the axillary nerve.
Signs include loss of sensation in the arm and paralysis and atrophy of the deltoid, biceps, and brachialis muscles.
Characteristically 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 the arm’s power of flexion of the elbow is lost, as is also supination of the forearm.
This classic physical position is commonly called “waiter’s tip”.
If the insult occurs in early age it may stunt the growth in the affected arm with everything from the shoulder through to the fingertips smaller than the unaffected arm.
This also leaves the patient with impaired muscular, nervous and circulatory development, leaving arm with almost no ability to regulate its temperature.
Damage to the circulatory system reduces the healing ability of the skin, so that skin damage takes far longer
The arm is weakened and cannot be lifted.
Loss of sensory perception is usually between the shoulder and the elbow.
The most common cause of Erb’s palsy is dystocia, an abnormal or difficult childbirth or labor, difficulty of shoulders passing through the birth canal, excessive pulling on shoulders with head first delivery, and by pressure on raised arms during breech delivery.
It can also affect neonates affected by a clavicle fracture unrelated to dystocia.
Following trauma to the head and shoulder, an injury can cause the nerves of the plexus to violently stretch, with the upper trunk of the plexus sustaining the greatest injury.
Other Injuries as a result of direct violence, including gunshot wounds and traction on the arm can cause nerves related paralysis.
The appearance of the affected arm varies.
Sometimes the arm may lack the ability to straighten or rotate but otherwise function normally giving the overall appearance of the arm to be stiff and crooked.
The arm may appear to have little to no control and has a loose appearance.
In some cases patients may suffer discomfort and pain, as the severity of the condition can vary, some patients may experience no pain at all and for their affected arm to simply be visually crooked.
Extreme nerve pain is mostly common during the final stages of growth.
Patients may complain about strained muscle, stiffness, circulatory problems and cramps.
Discomfort in the shoulder blade is common in Erb’s palsy and the shoulder is often at risk of dislocation.
Neurosurgery is often required for avulsion fracture repair.
The three most common treatments for Erb’s palsy are nerve transfers from the opposite arm, subscapularis releases and latissimus dorsi tendon transfers.
Nerve transfers are usually performed under the age of 9 months since it increases the effectiveness of the procedure, and if done at an older age more harm than good is done, aa a result of nerve damage in the area from which the nerves were taken.
Subscapularis releases provide stretch within the arm, and can be carried out at almost any age and can be carried out repeatedly.
Subscapularis release does compromise the integrity of the muscle.
Latissimus dorsi tendon transfers involve cutting the latissimus dorsi in half to pull part of the muscle around and attach it to the outside of the biceps.