Injuries to the Brachial Plexus
At the side of the neck on each side the nerves exit from the spinal areas at each level and join and separate in a complicated manner in what is anatomically called the brachial plexus. This nerve collection runs down from the neck to the armpit where it separates into the individual nerves of the arm. The plexus is well placed to be easily injured in knife wounds, bullet wounds, sudden traction (stretch) and direct blows. Because of the severity of the injury and limited recovery, a brachial plexus lesion can leave someone with a painful arm of very limited use.
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.
Estimation of brachial plexus injuries is difficult to make and they are not common, occurring mostly in young men as does most trauma. Narakas, who treated over a thousand brachial plexus lesions, explained a rule of seven seventies about this kind of injury:
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 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
Wrenching the neck and the arm away from each other at the shoulder can do considerable damage to the nerves in the plexus which varies from causing a stretch injury to pulling their connections out of the spinal cord. If the nerves are ruptured close to the spinal cord the chance of recovery or surgical reconstruction is limited. This is distinguished from ruptures which occur further away from the spinal cord which have a better potential outcome. Higher injuries involving C5 and C6 nerves are more common if the arm is at the side at the time of injury and lower nerves involving C8 and T1 are more typically damaged when the shoulder is violently moved overhead. Lower lesions are more common.
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.
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.
During the long period waiting for any improvement, often up to 18 months, it is difficult to manage the problems such as development of chronic pain, arm swelling and maintenance of the normal ranges of the joints. Physiotherapists are closely involved in the maintaining of healthy joints and the strengthening of recovering muscles. The restoration of functional muscle strength by surgical intervention is more predictable in younger people.