More Clinical Testing for Neuropathy

Following on from yesterday's post, today's articles from The Foundation for Peripheral Neuropathy (see link below) talk about alternative clinical tests to establish if neuropathy is present. The blog has already covered EMGs and tissue biopsies but doctors can also carry out Quantitive Sensory Testing (QST); Autonomic Testing and Lumbar Punctures (Spinal Taps). The following describes how and why but remember, many many people are tested for neuropathy without definitive results but this doesn't mean that they don't have it (the symptoms are pretty much unique to the disease). This is then referred to as Idiopathic Neuropathy.

Quantitative Sensory Testing (QST)

What is it?
Quantitative sensory testing (QST) is a method used to assess damage to the small nerve endings, which detect changes in temperature, and the large nerve endings, which detect vibration.

Why do it?
QST is used to diagnose and assess the severity of nerve damage, especially in the small nerve endings. It can also help determine if a neuropathy is responding to treatment. It is used to diagnose many different types of neuropathies, including peripheral neuropathies. It may also be used to identify where the nerves are damaged.

How is it performed?
QST uses a computer testing system to measure how the nerves involved react to vibration and changes in temperature. The test results are compared to a series of "normal" patients as well as to the patient's unaffected side.

How will it feel?
Depending on the specific test, the patient will feel mild vibrations and hot and cold sensations. The procedure is non-invasive—no needles are used. Overall, little or no discomfort should be felt during the test.

Autonomic Testing

Autonomic tests measure how the systems in the body that are controlled by the autonomic nerves respond to stimulation. The data collected during testing will indicate if the autonomic nervous system is functioning as it should, or if nerve damage has occurred.

What is it?
The nervous system has three parts: motor, sensory and autonomic. The autonomic system manages all internal functions such as blood pressure, blood flow, and sweating. Autonomic tests are conducted to see if the autonomic nervous system is functioning normally.

Why do it?
Autonomic testing can help determine if a patient is suffering from certain diseases that attack the autonomic nervous system, or as a way to diagnose an illness, or source of pain.

How is it performed?
To see if a disease is affecting the autonomic nervous system, several tests are done to monitor blood pressure, blood flow, heart rate, skin temperature, and sweating. By measuring these functions, it is possible to discover whether or not the autonomic nervous system is functioning normally.

Tests to measure blood pressure and heart rate include the tilt table test, a deep breathing test and the Valsalva maneuver. The tilt table test requires that the patient lie on a table that is then raised. The deep breathing test requires the patient to take deep breaths for a minute. The Valsalva maneuver requires that the patient blow into a tube to increase pressure in the chest. While these simple tests are performed, blood pressure and heart rate are monitored.

The Quantitative Sudomotor Axon Reflex Test (QSART) described separately, is another autonomic test performed to measure sweating and skin temperature.

How will it feel?
All testing is non-invasive and painless.

Lumbar Puncture (Spinal Tap)

What is it?
A cerebrospinal fluid (CSF) test (also known as a lumbar puncture or a spinal tap) is the most common method of collecting a sample of a patient's spinal fluid. The cerebrospinal fluid, normally clear and colorless, surrounds the brain and spinal cord and acts as a buffer. Any changes in the fluid's color, consistency or quantity may indicate a neurological disease or disorder.

Bacteria or increased numbers of white blood cells in the CSF will make it appear cloudy and may indicate an infection in the brain or spinal cord such as meningitis or Lyme disease. High protein levels are often a sign of a spinal cord tumor or an acute peripheral nerve disorder such as Guillain-Barré syndrome (GBS) or chronic inflammatory demyelinating polyneuropathy (CIDP). Abnormal antibodies may suggest multiple sclerosis. A variety of diseases, including meningitis and brain tumors, can increase the fluid's pressure.

Why do it?
To identify the presence of an autoimmune disorder, such as GBS or chronic inflammatory demyelinating polyneuropathy (CIDP), a sample of the patient's cerebrospinal fluid often must be analyzed. In a patient with GBS or CIDP, the fluid will contain more protein than usual, with no increase in the number of white blood cells or pressure.

How it's performed:
In the procedure, the patient is positioned lying on his/her side. A small anesthetic is injected into the skin in the middle of the lower back. A long, thin needle is inserted into this region and in the spinal canal. The CSF pressure is measured and fluid is collected for testing. After the sample is collected, the needle is removed and the patient must remain flat, or nearly flat, for an hour to two after the test.

A lumbar puncture with fluid collection may also be part of another procedure, particularly a myelogram (a CAT scan after dye has been inserted into the CSF).

How it will feel:
Overall, discomfort from the procedure is minimal. The entire procedure usually takes about 30 minutes. The actual pressure measurement and fluid collection take only a few minutes. Some patients experience headaches, hours or days after the test. These headaches almost always disappear spontaneously over time.

http://www.foundationforpn.org/livingwithperipheralneuropathy/evaluation/qst/index.cfm