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What is it?

The Brachial Plexus

The brachial plexus consists of the five nerve roots CS C6 C7 C8 and T1, that come out of the spinal cord at the cervical level.

These roots merge to form the spinal nerves which themselves become the upper trunk (C5 and C6), the middle trunk (C7), and the lower trunk (C8 and T1). Found under the clavicle, these trunks reorganize to form the distal branches; musculocutaneous nerve, axillary nerve, ulnar nerve, radial nerve and median nerve.

The lesion

During difficult birth delivery of large children, in breech delivery of smaller babies or in other circumstances, the roots may be pulled and injured. This traction injury may result in elongation in continuity of the nerve, extra foraminal rupture, or avulsion from the spinal cord.

We find very often that the upper roots, C5 or C6, are mostly ruptured and that the lower roots, C8 or T1, are usually avulsed. This is due to the anatomical disposition of the roots. The resulting paralysis reflects the number of affected roots although there is no precise relationship between a root and a precise paralysis. Most of the roots overlap.

It is understandable that a root avulsed from the spinal cord will not recover at all. There is no way that any nerve fiber may come from the spinal cord and colonize the nerve.

In the traction injury, if the nerve sheath is still preserved, the fibers may grow again and there is a good chance for spontaneous recovery to occur. If the nerve sheath is affected, the nerve will grow and some of the fibers may join the distal part to allow for some minor signs of recovery but these fibers will be limited and give poor muscular activity.

A typical poor functional result after spontaneous recovery in a total palsy 

When diagnosing a case, it is very difficult to determine when the nerve sheath is intact or whether or not it has been disrupted.

For years, the surgeons have been trying to predict the possible recovery of a particular child in order to decide whether or not surgical exploration should occur. The problem is that the end result will not be precisely known for 2 or 3 years and at that point it will be too late for primary surgical repair. By that time, the target muscles are no longer alive and cannot be properly reinnervated. This is why several systems have been evaluated in order to predict the result and determine the necessity for surgical repair.

In 1977, with TASSIN, we followed a large number of children from birth to three years of age who did not have primary surgical repair. We were able to correlate the end-result with the extent of the injury and age of recovery. We found that if the biceps muscle had not recovered by 3 months of age, the quality of the end result was generally poor. If the biceps had recovered before 3 months of age, the final result of the limb was quite good.

It was then decided that:

Most teams in the world use this schema although some will wait longer or use different scales.

If the baby has a complete paralysis of the upper extremity it is a little different: in this case the most important factor is the hand recovery.

In these case another sign of severity is the Horner's syndrome: on the side of the paralysis, the eye is slightly closed, with tears and myosis. This sign usually correspond to an avulsion of the T1 root from the spinal cord.

Horner's sign in the right eye in a total palsy 

The time factor is very important.

If one has waited too long, the decision is very difficult as some recovery will have occurred but the repair will restart the recovery process from zero and there will be some post-operative loss of function. It is difficult for a family to accept an immediate loss for the hope of an hypothetical late recovery.

Primary nerve surgery is still possible, and may give good results in older babies (2-3 years, sometimes more) but the psychological barrier is very important.