Diagnostic tests for peripheral neuropathy

Your nervous system and peripheral neuropathy

Your nervous system is divided into the central nervous system (made up of your brain and spinal cord) and your peripheral nervous system. Your peripheral nervous system sends messages back and forth between your brain and the rest of your body; it helps to control your muscle movements and your ability to sense things like pain and temperature (hot or cold).

When one or more nerves are hurt by an injury, disease, or for no apparent reason they just start to “malfunction”, it can cause an uncomfortable condition called neuropathy. Neuropathy is a problem with how these nerves act, or “talk” to other parts of the body. In some cases, the messages don’t get through properly, resulting in numbness or tingling.  In other cases, the result is pain without any apparent reason for feeling it. Neuropathy of the peripheral nerves is often called peripheral neuropathy.

When the peripheral neuropathy results in the lack of ability to feel pain or temperature, it can result in the loss of an important protection and warning system for your body.  As you lose the ability to sense things, your risk of injury increases. Injuries that would normally cause pain such as getting a splinter in your hand or wearing shoes that create a blister, can become much bigger problems. People with numbness due to this type of peripheral neuropathy need to inspect the area regularly, for things they don’t feel.

Sometimes the neuropathy results in pain, called peripheral neuropathic pain, in the absence of any injury at all.  This can be quite bothersome, and sometimes very disruptive to daily living.  Often, when no longer distracted by other things, such as when  trying to sleep, sufferers of this type of pain are kept awake by its nagging nature. Other times, buttoning a shirt, or putting on a pair of shoes can make the pain fly out of control, increasing burning and tingling.

What usually causes peripheral neuropathy?

Peripheral neuropathic pain can be caused by a variety of conditions or problems:

  • Diabetes
  • Vascular disease
  • Physical injury to a nerve
  • Poor nutrition or vitamin deficiencies
  • Alcoholism
  • Repetitive stress injury
  • Exposure to toxins (poisons)
  • Infections
  • Hormonal diseases, like an overactive thyroid gland
  • Pressure on one or more nerves (from a cast on an arm or a leg, or a tumor, for example)
  • Autoimmune diseases like lupus
  • Chemotherapy treatment for cancer or HIV

How is peripheral neuropathic pain diagnosed?

Since there are so many possible causes of peripheral neuropathy, it may be hard for some health care providers to make the diagnosis. There are many symptoms that are not clear or specific so a lot of detective work may be required. Also, while the symptoms may develop rapidly over a period of days, they often slowly progress over weeks, months, or even years, so that the change may be hard to determine.

The diagnosis of peripheral neuropathy will often mean a referral to a specialist, like a neurologist, a doctor who diagnoses and treats problems with the nervous system. The specialist will start by learning as much as possible about your detailed medical history. He or she will ask when your symptoms started, how they developed, and how much – and what type – of pain you have. The doctor will ask about other health problems, medications that you take now or have taken in the past, and the health problems of other family members.

The next step is often a full neurological examination, including testing your reflexes, balance, and even your muscle strength. You will be tested to see whether you can sense different levels of touch, vibration, and heat or cold. For instance, the doctor might touch your skin lightly with a piece of cotton or wool, or with a pointed wooden stick or a tuning fork, or ask you to hold an ice cube. The doctor is checking to see if you feel unusual amounts of pain when touched with certain objects, or if you have no feeling at all in some parts of your body.

The specialist may also want to check for other illnesses that might be causing your neuropathy, so that these problems can be treated. This may mean ordering blood and urine tests to look for signs of infections, diabetes, vitamin deficiencies, kidney, liver, or thyroid problems, and autoimmune or genetic diseases.

Special tests to help make the diagnosis

Based on the results of these tests, your doctor may want to order further tests to learn more about your neuropathy, in order to be able to treat it properly. Some of the most helpful tests are:

  • Blood tests: To detect things like diabetes, vitamin deficiencies, liver or kidney problems, and even immune system problems.
  • Muscle strength studies: To determine whether or not muscle function is a problem as well, or whether other neurological conditions are present, such as multiple sclerosisNerve conduction study: A nerve conduction study shows how fast your nerves are able to send their electrical signals to each other. It also shows the strength of those signals. This test tells your doctor which parts of your nerves are most affected.
  • Electromyography (EMG): This test measures the electrical activity of one or more of your muscles while they’re being flexed, or while your arm (for example) slowly bends. It shows how well your muscles are receiving messages from your nerves.
  • CT scan or magnetic resonance imaging (MRI): These tests can check whether cysts, tumors, blood vessels, or bones are rubbing against or squeezing one or more nerves in your body.

Patience is required while diagnosing peripheral neuropathy, as no stone can be left unturned. It may take a significant amount of time to get all of your test results, interpret them, and proceed to other tests, but they are critical to help figure out what’s going on. It can sometimes get frustrating. A good way to think about it is that the diagnosis of peripheral neuropathy is usually made when other diagnoses have been taken off of the possibility list. Once your health care provider has determined that peripheral neuropathy is the problem, they will then be able to decide on the best possible treatment.

 

Resources:

 

The Neuropathy Association
http://www.neuropathy.org

National Institute of Neurological Disorders and Stroke (NINDS)
http://www.ninds.nih.gov (search on “neuropathy”)

National Diabetes Information Clearinghouse (NDIC)
http://www.diabetes.niddk.nih.gov Medline Plus

http://www.nlm.nih.gov/medlineplus (search on “neuropathy”)

Mayo Clinic
http://mayoclinic.com (search on “neuropathy”)