There have been cases of patients who have lost complete sensory perception within the arm after procedures whereas they had full sensory perception before. The most common area for a loss of sensory perception (except where the arm faces a total loss) is between the shoulder and the elbow, since the nerves which provide information from that area to the brain are also those first damaged in the initial causative trauma. Cause
The most common cause of Erbs palsy is dystocia,  an abnormal or difficult childbirth or labor. For example, it can occur if the infants 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 cephalic presentation (head first delivery), or by pressure on the raised arms during a breech (feet first) delivery. Erbs 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. Diagnosis
The appearance of the affected arm (or arms) depends on the individual case.
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. History
The renowned British obstetrician William Smellie is credited with the first medical description of an obstetric brachial plexus palsy. In his 1768 treatise on midwifery, he reported a case of transient bilateral arm paralysis in a newborn after difficult labour. In 1861, Guillaume Benjamin Amand Duchenne coined the term "obstetric palsy of the brachial plexus" after analyzing four infants with paralysis of identical muscles in the arm and shoulder, after publishing his initial findings in 1855. In 1874, Wilhelm Heinrich Erb concluded in his thesis on adult brachial plexus injuries that associated palsies of the deltoid, biceps and subscapularis are derived from a radicular lesion at the level of C5 and C6 rather than isolated peripheral nerve lesions.