What is Erb's Palsy?
Erb's palsy is one form of obstetric brachial plexus injury. The likelihood of an obstetric brachial plexus injury is 0.5-2.6 per 1000 full-term live births. The brachial plexus typically is composed of five collections of nerve fibers that emanate from the spinal cord. These five nerves are the lower four cervical and first thoracic nerve roots (C5 to C8 and T1). These collections intermingle and exchange nerve fibers as they progress from the spinal cord to the axilla (arm pit region). They then enter the arm as named nerves. The nerve fibers composing the brachial plexus, like other nerve fibers, convey information about the environment (sensation) and permit action to be taken on the environment (movement through muscle contraction). Consequently, disruption of these fibers results in loss of sensation and muscle weakness or paralysis involving muscles of the shoulder region and upper extremity. Erb’s palsy is the damage of C5-C6/ superior (upper) trunk of the plexus. It causes weakness of shoulder and elbow movements.
What causes Erb's Palsy?
Erb's palsy is generally caused by traction (stretching) of the nerve fibers of the brachial plexus when the head and shoulder are moved in opposite directions. This may occur following delivery of the head when the head is deviated away from the shoulder so that the shoulder can clear the birth canal (i.e., shoulder dystocia). This type of brachial plexus injury also follows cesarean section deliveries, indicating that it is not simply an indication of a poorly performed delivery. Reported risk factors include large infants, small mothers, low or midforceps delivery, vacuum extraction, second-stage labor exceeding 60 minutes, and delivery of a previous infant with an obstetric brachial plexus injury.
How is Erb's Palsy diagnosed?
The diagnosis is based on the physical examination and certain tests. These tests usually include an EMG (to test the integrity of the nerve and muscle fibers) and an imaging study (MRI or CT – myelogram).
How is Erb's Palsy treated?
Although obstetric brachial plexopathies were first described in 1764, their management remains controversial. The severity of the injury ranges from partial to complete involvement of the affected nerve fiber collections. Although many reviews suggest that some spontaneous recovery occurs in more than 90% of affected individuals, the natural history is unknown. Studies in which surgical intervention was not employed have reported significant later life impairment in at least 20% to 25% of patients. Unfortunately, testing does not identify this subset of individuals. Consequently, watchful waiting typically is employed. Since surgical intervention yields the best results when performed during the first year, the observation period typically is less than this (e.g., 3 to 9 months). During this time, physical therapy is employed.
More information on Erb's Palsy
National Organization for Rare Disorders
United Brachial Plexus Network
Erb's Palsy Association of Ireland