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Diagnosing Neuropathy: The Key to Understanding the Cause
Norman Latov, M.D., Ph.D.

The first step towards effectively managing peripheral neuropathy is to correctly diagnose the cause. Your best bet is to consult with a neurologist specializing in neuromuscular diseases or neuropathy, who would know what further evaluation or testing is required.

Complete Clinical History and Neurological Evaluation
The neurologist begins by taking a complete medical history to learn about your symptoms’ onset, progression and pattern of involvement, as well as find out about any co-existing medical conditions, previous treatments, and medications. Bring in copies of relevant medical records or previous evaluations, but go through the materials first to avoid overwhelming the physician with duplicate or unrelated information. A complete clinical assessment—including a careful past medical history, medication history, and family history—provides valuable clues towards determining the cause(s) and solving the puzzle. 

Next, the neurologist performs a complete neurological examination to identify the type, distribution or severity of the neuropathy.  Both motor and sensory nerve functions are evaluated by testing strength and sensation, as well as such integrative functions as balance, coordination, and reflexes.  Information about the autonomic nervous system can be obtained by testing for variation in heart rate and blood pressure in the lying and standing positions. Improvement or progression can be evaluated by repeated testing at follow-up visits.

There are a number of procedures that help evaluate the neuropathy. These include:

Electrodiagnostic Tests
There are two electrodiagnostic tests that are the most helpful and commonly used in evaluating peripheral neuropathy:

  • Nerve Conduction Studies:  evaluates how the nerves transmit electrical stimuli. The nerves are like electric cables that are made of of wires (axons) wrapped by insulation (myelin). In addition to providing information about the severity and distribution of the neuropathy, these studies help identify whether the neuropathy primarily involves the axons or the myelin sheaths.
  • Electromyography (EMG):  measures the electrical activity of muscles in response to nerve stimulation.

Skin Biopsy
Small fiber neuropathy cannot be diagnosed with EMG and nerve conduction studies that only measure the large fibers. Consequently, if your neurologist suspects this type of neuropathy, a skin biopsy may be done to measure the density of the epidermal small nerve fibers (those fibers in your skin).  In cases of sensory neuropathy, this biopsy technique can detect loss of epidermal nerve fibers before the changes are revealed with electrodiagnostic tests.

Autonomic Tests
The Quantitative Sudomotor Axon Reflex Test (QSART) measures the autonomic nerve fibers that stimulate sweating. A tilt table test, which measures your changes in blood pressure and pulse from when you are prone (lying down) to when you are vertical (standing up) can also be performed to detect  autonomic nerve involvement.

Nerve Biopsy 
A nerve biopsy provides tissue for pathological examination.  It can show vasculitis or inflammation of the blood vessels, abnormal deposits of substances such as amyloid, or occasionally demyelination that is missed by electrodiagnostic studies.  The sural nerve at the calf is most often biopsied, as its function is limited and rarely missed. There is a chance of lingering pain, so that a biopsy is usually only done if the neuropathy is progressive, and other tests failed to identify a cause.

Other Testing

In addition to these procedures, the neurologist may order a number of blood and urine tests, as well as radiologic tests to help find the cause. These include tests for diabetes, autoimmunity, infections, nutritional deficiencies, toxins, hereditary conditions, and certain cancers, among others.

Treatment of the neuropathy depends, in part, on the underlying cause. If no cause can be found, the neuropathy is called idiopathic, and in which case it can be helped with medications to help control the pain, or with physical therapy. With your on-going support The Neuropathy Association will continue to work to find a cure.

 

 

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