Brachial plexus injuries

Written by Dr Richard Lawson FRACS - Hand Surgeon

What is the brachial plexus?

The brachial plexus is a group of very important nerves that runs from the neck into the shoulder and arm, controlling all the movements and sensation of the arm. The nerves are large, around 5mm in diameter, and branch and intermingle in a complex fashion. The nerves start at the spinal cord, pass out between the vertebrae in the neck, run across the space from the neck to beneath the collar bone, and then run into the arm.

As the nerve branches leave the spinal cord they form 5 major bundles, called roots. These are labelled the C5, C6, C7, C8 and T1 nerve roots; the C refers to cervical and the T to thoracic, thus the C5 nerve root is the 5th cervical nerve root.

How is the brachial plexus damaged?

The two main groups of patients with brachial plexus injuries are babies and young adults (usually males). In babies, the plexus can be torn if the baby’s head and shoulder are pulled in different directions during delivery; this typically happens in big babies and difficult deliveries.

The other major group is of young adults exposed to major trauma, such as falls from motorbikes. In these patients the head and shoulder are usually pulled in opposite directions as the helmet hits the ground. Huge forces are developed, and these can lead to extensive damage to the plexus. The force of the accident can also lead to injuries to other structures in the region, such as the neck, collar bone and shoulder.

The prognosis for recovery is best when there is less trauma; thus, the vast majority of babies with an injured brachial plexus improve, while spontaneous improvement is less likely in adults with traumatic injuries.

In the most common pattern of injury the upper nerve roots are damaged (that is the C5 and C6 nerve roots), and this kind of injury is particularly common in babies, most of whom go on to recover. Patients with this kind of injury have difficulty lifting the arm to the side, and flexing the elbow up, but tend to have excellent hand function.

The less common and more severe pattern of injury involves damage to all the branches of the brachial plexus, and in the most severe cases can lead to a flail arm which dangles by the patient’s side, with no function. This is usually seen in high speed motor cycle injuries.

How are brachial plexus injuries managed?

It is important to have an early assessment of the injury by an experienced brachial plexus surgeon, as there is a group of patients that is best managed by early surgery.

Following an assessment by the brachial plexus surgeon, a number of tests are usually ordered. These will often include an X-ray of the neck, to rule out fractures of the neck vertebrae, an X-ray of the collar bone and shoulder to rule out fractures of these bones, and often a chest X-ray to check for rib fractures and to see how the diaphragm is functioning. Electrical studies are also usually ordered to assess the electrical status of the nerves and the muscles that these supply. An MRI may be ordered to look at the nerve roots as they come out of the neck.

After a full assessment, physiotherapy is usually prescribed to maintain good movements in all of the joints that have been affected, whilst waiting for recovery of the nerves or awaiting surgery.

Surgical management of the brachial plexus injury

Most injuries to the brachial plexus spontaneously recover, but a small proportion does not, and these patients are best managed with surgery. The aim of the surgery is to reconnect the muscles that have lost input from their nerves. In some cases, the nerves can be repaired, either directly with sutures between the nerve ends, or much more commonly with a nerve graft, which is a strip of nerve which is taken from the leg and placed between the two ends of the nerve.

In other cases the nerve had actually been pulled out of the spinal cord (avulsed) and in these cases the nerve cannot be repaired. Injuries like these require a different approach, which involves taking undamaged nerves and joining them to the damaged nerve. Another approach typically used for injuries where all nerve roots are avulsed is to aim for some finger and elbow movement using muscles taken from the leg and connected to functioning nerves such as those that supply the rib muscles.

In some cases, the muscles that are supplied by the nerves have wasted away to the point that reconnecting them with their nerves will not lead to any return of function. In these cases, it is sometimes possible to take a muscle (which is not missed) from the leg, and to place it into the arm, to take the place of the wasted muscle. The new healthy muscle is joined up to arteries and to nerves in the arm.

What can be expected after repair of brachial plexus injuries?

Any return of function takes many months, as the nerves need to grow down from the repair site to the muscles, and this happens at less than a millimetre a day.

This period of waiting can be frustrating for the patient. During this time attempts to actively exercise the arm muscles are unproductive, but physiotherapy to maintain the range of motion of the joints is very important.

When the repaired nerve reaches the muscle and the muscle starts to contract the muscle can be exercised. At this point a slow but steady improvement in muscle strength usually occurs, over a period of many months. The muscle is never as strong as it was prior to the injury, but useful function can be obtained.

After surgical repair of a severe brachial plexus injury, movements of the shoulder and elbow flexion are usually most improved. In babies, hand movement is often regained, but this is not usual in adults.

It is common for other operations to be done at two to three years after injury to help improve function. This can involve stiffening joints that are not actively moving such as the wrist joint or rerouting tendons.