A number of tests can be used to confirm whether peripheral neuropathy is responsible for your symptoms. These include:
- nerve conduction test and electromyography (EMG)
- nerve biopsy
These are discussed in more detail below.
Nerve conduction test and electromyography (EMG)
A nerve conduction test measures the strength and speed of the signals transmitted through your peripheral nerves. The peripheral nerves are the network of nerves that run from your brain and spinal cord to and from other areas of your body, such as your limbs and organs.
During a nerve conduction test, small metal discs called electrodes are placed on your skin. The electrodes release small electric shocks that stimulate your nerves. The speed and strength of the nerve signal is measured. An unusually slow or weak signal could indicate peripheral neuropathy.
Some types of peripheral neuropathy cause a distinctive change in the pattern of electrical activity, which can be detected using electromyography (EMG).
EMG involves having a small needle-shaped electrode inserted through your skin and into your muscle. The needle is used to measure the electrical activity of your muscles. Before having the procedure, an anaesthetic (painkilling) cream will be rubbed into your skin so the electrode does not cause any pain.
Both types of test are usually carried out at the same time to obtain a more detailed assessment of how well your nerves and muscles are functioning.
A nerve biopsy is a minor surgical procedure where a tiny sample of a peripheral nerve is removed from your leg for testing.
Peripheral neuropathy can cause physical changes to the shape of the nerve, which can be seen under a microscope. The biopsy is carried out under local anaesthetic, which means you will be awake but unable to feel any pain.
Identifying the cause
Identifying an underlying cause is an important aim of diagnosing peripheral neuropathy. In many cases, identifying the underlying cause is relatively straightforward.
For example, if diabetic polyneuropathy is suspected, a diagnosis can usually be confidentially made by asking you about your symptoms, carrying out a physical examination and checking the levels of glucose in your blood and urine.
Alternatively, if you are taking a medication that is known to cause peripheral neuropathy, temporarily stopping or reducing your dose to see whether your symptoms improve will help confirm whether that medication is responsible.
If no obvious cause is suspected, you will probably be referred for a series of more extensive blood tests to check:
- whether you have an infection that may be responsible
- how well certain organs, such as your liver and kidneys, are working
- the levels of nutrients in your blood, such as vitamin B
- whether you have any defective genes that are known to cause conditions associated with peripheral neuropathy, such as Charcot-Marie-Tooth disease, a condition that causes damage to the nerves, particularly in the feet
If the results of these blood tests are still inconclusive, you may be referred to an oncologist, a cancer specialist, to check that your symptoms are not a complication of cancer, such as lymphoma (cancer of the lymphatic system) and multiple myeloma (cancer of the bone marrow).
Tests that your oncologist may carry out include:
X-ray, where radiation is used to study your bones
computerised tomography (CT) scan, where a scanner is used to take a series of X-rays, which it then assembles into a more detailed image
magnetic resonance imaging (MRI) scan, where strong magnetic fields and radio waves are used to produce a detailed image of the inside of the body
biopsy, where a sample of suspected cancerous tissue is removed so that it can be tested in a laboratory