Brachial Plexus Lesions Pain and Surgery
by Jonathan Blood Smyth
Stretching or traction injuries are the most difficult to treat as the status of the nerves is not accurately known, with early surgery potentially preventing normal recovery and delaying surgery perhaps permitting important structures to degenerate. 3-6 weeks after injury is the time surgical intervention would be contemplated if the nerve roots have been avulsed from the spinal cord. If expected recovery from less severe injury is not forthcoming then exploration can occur at 3-6 months from injury. If the nerve has been cut or avulsed then nerve repair or nerve grafting can be performed respectively, with nerve transfers sometimes used to speed recovery.
A very difficult part of brachial plexus lesions is the unexpected pain which can develop with time. Even though the nerves have been pulled out from the spinal cord connections, a chronic pain problem can develop in the area the nerves supply normally, which is the arm. As the nerves transmitting impulses to and from the spinal cord have been severed by being forcibly disconnected, the spinal cord nerves which normally receive their inputs are deprived of this. These nerves change and start transmitting signals spontaneously, generating an abnormal pain problem which can be unpleasant and persistent.
Patients typically describe the pain as shooting, crushing or burning, severe or coming on in severe spasms. This kind of pain is referred to as deafferentation pain, which refers to the rupture causing a loss of incoming (afferent) signals to the nervous system. Treatment of deafferentation pain starts with conservative measures. A pain management team specialises in these conditions and early involvement would be helpful, even admission to allow treatment to be started with a multidisciplinary approach. Many drugs can be used apart from the morphine chemicals and some may be helpful in suppressing this neuropathic pain.
TENS, transcutaneous nerve stimulation, is a physical modality for pain control which sends signals into the spinal cord to affect the pain gating system and may be useful in some cases. It can take a long time for an effect to be forthcoming and for the best outcome to be clear. There are a list of other treatments for brachial plexus lesions, none of them with much demonstrable success, including CBT (cognitive behavioural therapy), biofeedback, acupuncture, desensitisation and hypnosis. Due to the varied nature of the presenting symptoms a multidisciplinary team is vital to manage the patient over time.
Nonoperative treatment is complex and best managed by the dedicated multidisciplinary team which might include a physiotherapist, occupational therapist, physician and orthotist. The physician can manage the diagnosis and monitor the recovery, the orthotist will provide braces to prevent joint contracture, the occupational therapist will teach functional use and the physiotherapist will maintain joint ranges and encourage normal muscle use. Surgical care is highly specialised and should be undertaken only by specialists in designated centres with experience. Because the injuries vary so greatly the choice to intervene or not and the procedures to be chosen if surgery is to be attempted are very varied.
The outcome of a brachial plexus lesion is extremely variable as the mechanism of injury is so unpredictable and the results uncertain. The type of injury, the patient's age and the surgical treatment all affect the outcome. Muscle transfers, transferring a working muscle to do the work of paralysed ones, can be useful as can sural nerve (a nerve in the leg we can manage without) grafting, with many surgeons settling on surgery between three and six months after injury. Some surgeons have attempted to replace the nerve roots into the spinal cord but the results are not yet predictable, although success would dramatically change attitudes as healing in the central nervous system has not been usefully demonstrated.
Healing nerves progress at an average speed of one millimetre a day, which in imperial is about an inch or so a month. This can mean a very long wait if the injury is high up in the neck like the brachial plexus and without a nerve supply the nerve endplates on the muscle can degenerate which means the muscle won't work even if the nerve grows down to it in time. Much research is continuing into nerve growth factors which might speed up the recovery of direct nerve repairs and later grafting.