What are the Causes of Peripheral Neuropathy?
The peripheral nervous system refers to all the nerves outside of the brain and spinal cord. In practice these are usually nerves in your arms or legs. Nerves can be injured by a number of conditions and not all of these problems require surgery. Exposure to toxins such as elevated sugar in diabetes mellitus can result in permanent damage to these nerves that can be quite difficult to treat.
Conditions requiring surgery include entrapment of the nerve either by normal structures that enlarge over years or variants of normal structures that then go on to compress these nerves. Sometimes these entrapments are provoked by a traumatic event.
The other condition that requires surgery are growths on these nerves. The most common type is a nerve sheath tumour that is usually a benign (non-cancerous) abnormality. Rarely these growths can become malignant (cancerous).
These conditions can be quite difficult to diagnose. This is because they often have symptoms that mimic other conditions. Symptoms that may make one think about a peripheral nerve problem include pain or tingling that radiates down part of your arm or leg.
Signs and Symptoms of Peripheral Neuropathy
The pain, like any nerve pain, is often described as burning or shooting in nature. Some people will use the word electric to describe it. You may also experience pins and needles or itching in a similar distribution. Sometimes it will feel as if ants or water is running over the area even when there is nothing to see.
In the case of peripheral nerve tumour, you may feel a lump where the tumour is. Some of these nerves are deep in the limbs, so do not be concerned if you do not feel anything. If you push on the lump it may cause symptoms like those described above.
Diagnosis of a peripheral nerve condition will require specialist testing. This can include nerve conduction studies, done by a neurologist. This test measures how fast an electrical impulse moves through your nerve. During the test you may feel short sharp bursts of discomfort, but most people do not find the test too difficult. In cases of entrapment neuropathies, the conduction is slowed at the place where the nerve is compressed.
Other tests will vary depending on the condition being considered, but could include an ultrasound of the nerve or an MRI of the affected limb.
Treatment of the condition will depend on your specialist and your specific condition. Most entrapment neuropathies are treated with neurolysis. This means freeing up the nerve by cutting the ligament, band of tissue or scar tissue that is compressing the nerve.
Nerve transposition is advocated for some peripheral nerve conditions. The principle is that this moves the nerve to a place where it is less likely to be compressed. This is controversial, as not all surgeons feel that this surgery results in improvement. One concern is that by moving the nerve small branches from the nerve are severed and blood vessels to the nerve can be disrupted. If this did happen, it could result in further damage to nerve function.
Nerve sheath tumours are removed if they are large or enlarging. They may also be operated on if they are superficial and easily bumped. Sometimes surgery on these abnormalities is done for cosmetic reasons.
These tumours arise from the outer layers that act as insulation for the nerve. This means that they can often be freed from the nerve without inherently damaging the nerve. This means that after surgery your nerve should work normally, although you may have mild sensory symptoms such as numbness that may improve with time.
In the diagram below shows the nerves of the upper arm. The median nerve I’s number 7 and ulnar nerve is number 8. Source: Netters Anatomy Flash Cards, Forth Edition 2014.
The following three images shows the process of a surgeon exposing a nerve, ready for surgery. Source: Core Techniques in Operative Neurosurgery 2011