Erb-Duchenne palsy

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Introduction0:00–0:26

Erb-Duchenne palsy, is named after the neurologists Wilhelm Erb and Duchenne de Boulogne who first described it. In this disorder, there’s paralysis to the muscles of the shoulder and the upper arm, and it happens when the nerves that innervate these muscles are damaged.
People with this disorder have their arm stuck in a position that looks like a waiter discreetly trying to get a tip, so it’s also called waiter’s tip deformity.

Physiology0:26–2:25

Okay, so the nervous system has two parts: the central nervous system, which consists of the brain, brainstem, and spinal cord, and the peripheral nervous system, which includes all of the nerves that fan out from the central nervous system.
Broadly speaking, the nervous system is split into an afferent and an efferent division. The afferent division brings sensory information from sensory receptors in the peripheral nervous system to the central nervous system, and the efferent division sends motor information from the central nervous system to organs like skeletal muscles, which causes them to contract.
Now, part of the peripheral nervous system are spinal nerves, which branch off the spinal cord. There are 31 pairs of spinal nerves, which are grouped into eight pairs of cervical nerves, twelve pairs of thoracic nerves, five pairs of lumbar nerves, five pairs of sacral nerves, and one pair of coccygeal nerves.
The brachial plexus is a network of spinal nerves that innervate the shoulder, arm, and hand, by supplying afferent or sensory nerve fibers from the skin, as well as efferent or motor nerve fibers to the muscles.
In terms of anatomy, the brachial plexus is divided into five roots, which come from the last four cervical nerves; C5, C6, C7, and C8, as well as the first thoracic nerve or T1.
The five roots will then combine to form three trunks: C5 and C6 merge to form the superior or upper trunk, C7 remains as the middle trunk, and C8 and T1 merge to form the inferior or lower trunk.
These trunks then form six divisions, which will regroup with each other to form three cords. These cords give multiple branches.
The main three are the musculocutaneous nerve, which is made up of contributions from C5, C6, and C7, the axillary nerve – which is made up of contributions from C5 and C6, and the subscapular nerve, which is made up of contributions from C5 and C6.

Pathology and Symptoms2:25–4:24

Erb-Duchenne palsy happens when there’s an injury to the C5 or C6 roots, or to the upper trunk that contains nerve fibers from these roots.
This injury commonly occurs to the infant during labor, in a condition called shoulder dystocia, which is when the baby gets stuck in the birth canal when one or both shoulders become trapped against the bones of the maternal pelvis.
When the baby is pulled out, the force could cause damage to the shoulder and the nerves in the brachial plexus. Although most common in infants, Erb-Duchenne palsy could affect people at any age when there’s shoulder trauma.
Okay, let’s look at what happens when someone gets this condition. First, the axillary nerve innervates the deltoid, which acts to abduct the arm, moving it away from the trunk.
So when the axillary nerve is damaged, the arm hangs by the side of the body. Next, the musculocutaneous nerve innervates the biceps brachii, which flex the arm at the elbow joint, and supinate the forearm, turning the palm anteriorly.
So when the musculocutaneous nerve is damaged, the arm extends straight at the elbow joint, and the forearm stays pronated, turning the palm of the hand posteriorly.
Finally, the subscapular nerves innervate the supraspinatus muscle, which helps the deltoid in abducting the arm, and the Infraspinatus muscle, which acts to laterally rotate the arm, moving it away from the midline of the body.
So when the subscapular nerve is damaged, the the arm can not abduct and it rotates medially, or towards the midline of the body.
When combined, we have what’s called “waiter’s tip deformity”, where the affected arm is adducted, and medially rotated, while the forearm is extended and pronated.
This gives the appearance of someone subtly asking for a tip, thus the name. All three nerves also carry sensory information from the skin of the arm, so it could also causes loss of sensation in some cases.
Finally, loss of innervation to the muscles in early life causes them to shrink, leaving the affected arm smaller and weaker than the unaffected one.

Diagnosis4:24–4:36

The diagnosis of Erb-Duchenne palsy is based on the history of damage to the affected arm and, and on physical examination to evaluate the appearance and function of the affected muscles.

Treatment4:36–4:56

Treatment isn’t needed in all cases of Erb-Duchenne palsy. Most babies recover within the first year, but others develop permanent arm weakness or paralysis.
Physical therapy is often used to aid in the recovery process. However, if Erb-Duchenne palsy does not resolve, surgical procedures like nerve transfers from the opposite healthy arm can be done.

Review4:56–5:20

All right, as a quick recap. Erb-Duchenne palsy occurs when there’s a disruption of the innervation to the muscles of the shoulder and the arm, caused by an injury to the nerve roots C5 or C6, or to the upper trunk of the brachial plexus.
The most common symptom is waiter’s tip deformity. Erb-Duchenne palsy is diagnosed by a physical exam, and is treated with physical therapy and surgery.