The Brachial Plexus is a group of nerves that exits from the cervical spine and travels along the side of the neck, under the clavicle and into the arm. This group of nerves has a complex series of interconnections and gives rise to branches that supply sensation and innervation to the muscles in the entire upper limb.
Injury to these nerves can result in profound functional loss in the upper limb.
Causes
During childbirth
The most common mechanism of injury is a stretching force across the neck. This is sometimes seen in birth trauma where the baby may become caught as it travels along the birth canal. This can result in the head being pulled forward in relation to the shoulders, resulting in a stretching force across the neck.
This can result in limitation of movement in the affected arm. In severe cases, the whole upper limb may be flaccid and have no active function.
Obstetric plexus palsy patients are monitored closely in the first few months of life to look for signs of spontaneous recovery. In many patients, the nerves will have been stretched and stunned, but will be able to recover spontaneously.
In severe cases, where there is no spontaneous recovery within the first six months or so, surgical intervention may be required.
Obstetric plexus palsy is often investigated with an MRI scan. This helps define the area of abnormality within the nerves and also identifies if the nerve roots have been pulled from the spinal cord.
Treatment
Surgical exploration allows identification of the area of injury and resection of damaged nerves. The defects are then grafted using nerves harvested from the legs. The recovery following nerve graft surgery is slow and the benefits may not become evident for several years. The aim is to try and restore shoulder and elbow movement so that the hand can be positioned for function.
Obstetric plexus palsy most often involves the upper portion of nerves in the brachial plexus. These primarily supply the muscles that control shoulder function and elbow function.
In adults
Adult brachial plexus injury usually involves a traction force between the side of the neck and the arm. This is commonly seen in motorbike accidents where the patient comes off at speed and the head is pushed to the opposite side resulting in a stretch of the nerves exiting from the neck.
The severity of the injury is variable and ranges from simple temporary stunning of the nerves through to complete disruption of the nerve supply to the limb.
Treatment
Current treatment in adults focuses more on nerve transfer surgery rather than nerve grafting surgery. If patients are failing to show spontaneous recovery in their muscle function, the transfer of nerves, or branches of nerves, directly to the muscle affected, may be performed.
The management of each patient with a plexus injury is unique and will be guided by the injury sustained and the amount of recovery that they achieve spontaneously. With all nerve surgery, the recovery is slow and the results may not become apparent for many months after the initial surgery.