As the individual nerve roots emerge from the neck they join together and separate in a complex fashion in an area called the brachial plexus, running down from the neck to the axilla where the individual arm nerves emerge. Nerves are very vulnerable structures and can be injured in gunshots, direct blows, knife attacks and traction injuries, which involve a sudden stretch. The results can be very disabling, with a chronically painful arm the patient is not able to move or use very well. Recovery is very variable and many patients have to cope with a less than useful arm.
Motorcycle injuries are the most common mechanism of brachial plexus injury, with severe traction occurring as the shoulder and head hit the ground, forcing the two structures apart and stretching the nerves severely. Wrenching the arm violently away from the body is a typical injury, with high speed car injury also providing many victims. Penetrating injuries from attacks with knives or guns or direct trauma from falls from a height or blunt objects can also give a brachial plexus injury.
It is difficult to estimate the number of this kind of injury and overall they are not common, with males in the 15 to 25 years old group affected preferentially as they are in many kinds of trauma. Narakas, a doctor, indicated his rule of seven seventies to explain the occurrence of these injuries:
Traffic accidents made up 70% of injuries and 70% were on motorcycles, of which 70% had multiple injuries
70% of those with multiple injuries had injuries above the clavicle area, so-called supraclavicular injuries.
70% of supraclavicular injuries involved one nerve root being avulsed (pulled out of the spine) and 70% of those were lower nerve roots in the neck, 70% of which generate a chronic pain problem.
If the neck and shoulder are moved apart suddenly with force there can be severe injury to the nerves of the brachial plexus with the nerve damage varying from a limited stretch to total nerve rupture from the spinal cord. If the connections are avulsed close to the spinal cord the picture is more serious and less likely to recover or be amenable to surgery. Further away from the spinal cord any rupture is more likely to have a good outcome. C5 and C6 injuries, the higher nerve roots, are more often damaged when the incident occurs with the arm by the side. C8 and T1 injuries, the lower nerve roots, are more likely injured when the arm is pulled suddenly overhead by the trauma.
A detailed examination of the arm may be necessary in a case of multiple injuries to ensure a brachial plexus lesion is not present. Typical symptoms are pain in the shoulder and neck, heaviness and weakness in the arm and abnormal sensations such as abnormal pain feelings or pins and needles. The shoulder can be very swollen and vascular injury from blood vessel traction should be suspected if pulses are absent or reduced. Medical examination of the reflexes, motor power and sensibility is performed to establish the nerves which have been injured and the degree of their injury. Testing for this can be difficult as nerve anatomy is variable and experience is necessary for interpretation.
Conservative management of lesions of the brachial plexus was common in the past, with waiting for any recovery the main strategy, recording the changes which occurred. By twelve to eighteen months after injury the recovery was considered to be complete, accepting that some further improvement could occur with time. The aim was to make the arm more stable, predictable and useful or amputate it if it could not be made so. Modern management emphasises recovery by early surgical treatment of open sharp object injuries to repair the nerves directly, with delayed intervention in blunt injuries.
It may take 18 months or longer to for any recovery to take place so it is difficult to maintain joint movements, manage the common chronic pain problem and control limb swelling. Restoring useful muscle strength by surgery is more effective if the patient is younger.