Nature of brachial plexus injury

Substantial stretching of nerve roots is possible before actual rupture occurs. Many
surgeons believe that rupture of the roots of the brachial plexus is frequent, and this
belief has dominated the treatment of traction injuries of the plexus. It is one of the12 R. BARNES
favourite arguments advanced in support of early operation. Nevertheless, Stevens (1934)
stated that rupture of nerve roots with complete separation of the torn ends was a rare
lesion, and this view is supported fully in this series by observations made at the time of
operation. Ten severe injuries of the brachial plexus were explored and in only one patient was there complete rupture of the nerve roots. Moderate stretching of a nerve root causes temporary inhibition of conductivity which
affects the motor rather than the sensory fibres. There is no degeneration of the nerve distal
to the lesion and complete recovery occurs within two months of injury.
Traction injuries of greater severity cause a degenerative lesion of the axons but no
disturbance of the internal architecture of the nerve. Spontaneous recovery of function
may be expected, though it is slow because many regenerating axons have to travel long
distances before connection with their end-organs is established. With proper treatment,
complete recovery may be expected, though not in the intrinsic muscles of the hand. Failure
of recovery in these muscles may be explained by irreversible changes occurring in the motor end-plates before the axons re-establish connection with them.
Traction injury of still greater severity causes disruption of the axons and considerable
damage to the intraneural blood vessels and connective tissue. Intraneural scarring is then
inevitable ; recovery is patchy and incomplete, or it may even be prevented altogether.
Very great violence may rupture one or more roots of the plexus. The rupture is never clean cut, and it is always associated with severe scarring of both stumps for some distance on each side of the rupture. For this reason it is impossible to perform satisfactory end-to-end. suture of the ruptured nerve after adequate resection of the stumps, and nerve grafting is
the only feasible method of restoring continuity.
Most brachial plexus injuries are mixed lesions, for there is wide variation in the traction
violence applied to individual nerve roots. All traction injuries are of considerable extent and, in the more severe lesions, several centimetres of the nerve may suffer gross intraneural
damage. It is important to appreciate that it is intraneural damage, and not extraneural
scarring caused by associated soft tissue injury, which is the barrier to recovery.