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.
The commonest mechanism of injury is a traction injury where the arm is wrenched suddenly away from the body, with the neck in some cases travelling the opposite way, adding to the stretch. The commonest reasons for this kind of injury are motorcycle injuries where the shoulder and the head are stretched apart as the person hits the ground with speed, with high speed car injuries also contributing. Penetrating injuries from knives, bullets or other objects in a fall, falls from a height and a direct blow from a hard object can all cause this 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 these had supraclavicular injuries, damaging the area above the collar bone where the brachial plexus lies
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.
The brachial plexus nerves can be badly damaged by the wrenching injury which occurs when the arm and the neck are violently moved apart. The damage varies from a minor stretch injury to the complete rupture of the nerves away from the spinal cord. Ruptures which occur close to the spinal cord are more serious and have limited scope for reconstruction or recovery. They differ from ruptures which are located further from the spinal cord which can have a better recovery potential. If the arm is at the side at injury then the higher nerve roots (C5 and C6) are more likely to be injured, whilst if the arm is wrenched overhead in the injury the lower nerves (C8 and T1) are more likely injured.
As brachial plexus lesions can be missed in cases of multiple injuries, it is vital to think about a detailed examination of the upper limb. Patients usually report pain in the neck and the shoulder, abnormal feelings such as bizarre pain symptoms and pins and needles and arm heaviness and weakness. Significant swelling may occur round the shoulder and if there are reduced or absent pulses then vascular injury from traction should be considered. The sensibility, muscle power and reflexes are assessed to figure out which nerves have been damaged and to what extent, a difficult job as it is very detailed and nerve anatomy varies between people. Experience is useful in making these judgements.
Typical past management of brachial plexus injuries was conservative, the patient recovering from the injury and the doctors would monitor the changes in the muscle power and sensibility over 12-18 months. Once the time had elapsed the remaining restrictions were considered permanent although small changes could still occur with time. The arm was treated surgically to make it more useful as a tool or by amputating it if it was in the way. Typical management now is surgical, with early exploration of open injuries (e.g. knife wound) and direct repair of nerves. In blunt trauma this might be delayed.
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.
