PERIPHERAL NERVE INJURIES
Brachial Plexus
The brachial plexus is formed by the anterior primary divisions of the C5-T1 nerve roots (Fig.13.3). The
plexus functions as the distribution center for organizing the contents of each peripheral nerve.
Upper plexus injuries (C5,6): The most common injury to the plexus involves compression or tearing of
the upper trunk. The mechanism involves shoulder depression and lateral flexion of the neck to the
opposite side.
There is loss of abduction and lateral rotation of the shoulder and weakness in elbow flexion and forearm
supination (waiter’s tip position). Erb’s palsy occurs with birth injuries when the shoulder is stretched
downward, although Benjamin5 cautioned that there are maternal and infant factors that could contribute
this injury in addition to the applied forces during delivery.
A “stinger” occurs with injuries as might occur when playing football and the individual lands on the upper
torso and shoulder with the head/neck laterally flexed in the opposite direction.
Middle plexus injuries (C7): Rarely seen alone.
Lower plexus injuries (C8,T1): Usually due to compression by a cervical rib or stretching the arm
overhead. Klumpke’s paralysis (paralysis of the intrinsics of the hand) occurs in birth injuries when the
baby presents with its arm overhead.5
Complete or total injury of the plexus: Complete paralysis from a total brachial plexus injury may occur
as a complication of birth; it is known as Erb-Klumpke’s paralysis and is associated with Horner’s
syndrome in one-third of those severely affected.5
NERVE INJURY AND RECOVERY
(1) First degree injury (neuropraxia): minimal structural disruption—complete recovery;
(2) second degree (axonotmesis): complete axonal disruption with wallerian
degeneration—usually complete recovery;
(3) third degree (may be either axonotmesis or neurotmesis)—disruption of axon, and
endoneurium poor prognosis without surgery;
(4) fourth degree (neurotmesis): disruption of axon, endoneurium, and perineurium—
poor prognosis without surgery;
(5) fifth degree (neurotmesis) complete structural disruption—poor prognosis without
microsurgery.
Recovery of Nerve Injuries
Nature and level of injury. The more damage to the nerve and tissues, the more tissue
reaction and scarring occur. Also, the proximal aspect of a nerve has greater
combinations of motor, sensory and sympathetic fibers, so disruption there results in a
greater chance of mismatching the fibers, thus affecting regeneration. Regeneration is
often said to occur at a rate of 1 inch per day, but rates from 0.5 to 9.0 mm per day have
been reported based on the nature and severity of the injury, duration of denervation,
condition of the tissues, and whether surgery is required.
Timing and technique of repair. Laceration or crush injuries that disrupt the integrity of
the entire nerve
require surgical repair. Timing of the repair is critical, as is the skill of the surgeon and
technique used to
align the segments accurately and avoid tension at the suture line for optimal nerve
regeneration. Different regenerative potential outcomes following nerve repair have also
been reported based on groupings of specific nerves.
• Excellent regenerative potential: radial, musculocutaneous, and femoral nerves
• Moderate regenerative potential: median, ulnar, and tibial nerves
• Poor regenerative potential: peroneal nerve
Age and motivation of the patient. The nervous system must adapt and relearn use of
the pathways once regeneration occurs. Motivation and age play a role in this,
especially in the very young and the elderly.