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.
The number of brachial plexus lesions is difficult to estimate as they are very variable and not common, being most common in fifteen to twenty-five year old males who make up a great preponderance of trauma victims. Narakas, who treated many of these injuries, indicated his rule of seven seventies:
70% were from traffic accidents of which 70% were motorcycle accidents and 70% of these had multiple injuries
Supraclavicular injuries, involving trauma to the area above the collar bone where the brachial plexus lies, made up 70% of these multiple injuries
70% of these had at least one nerve root pulled out or avulsed and 70% of the avulsed nerves were lower neck roots (C7, C8 and T1), 70% which were responsible for chronic pain
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.
In multiple injuries it is important to consider a detailed examination of the upper limb to exclude a brachial plexus injury. Patients complain typically of pain in the neck and shoulder, weakness and heaviness in the arm and abnormal feelings such as pins and needles and abnormal pain sensations. There may be significant shoulder swelling and if the pulses are reduced or absent then consideration should be given to vascular injury from the traction. The doctor performs a careful sensory, motor and reflex examination to indicate which nerves have been damaged and whether they are completely ruptured or still in continuity. This can be difficult as the anatomy of the plexus varies so experience is needed to interpret the results.
In the past most brachial plexus lesions were managed conservatively with monitoring over twelve to eighteen months to check any recovery of muscle power. After this time the deficit was considered to be permanent even though small amounts of improvement could occur over a longer period. Treatments were targeted at making the arm more useful or amputating it. Surgical reconstruction is now common and the timing of this varies, with open injuries e.g. from a knife being explored at the time and nerve repair performed. A three to four week delay can be appropriate in more blunt force trauma.
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.
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