Brachial Plexus Injuries
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.
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
70% of those with multiple injuries had injuries above the clavicle area, so-called supraclavicular injuries.
One nerve root was torn in 70% of the supraclavicular injuries, and 70% of nerve roots were the lower cervical ones, 70% of which were responsible for 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.
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.
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.