The goals of testing are:
- To diagnose the presence of neuropathy and distinguish it from other conditions that may cause similar symptoms
- Identify the cause of neuropathy, where possible
- Evaluate the location, extent, and severity of the nerve damage and assess organ function
- Identify underlying conditions that make neuropathy worse
- Detect and evaluate complications
The diagnostic workup for neuropathy begins with a thorough medical history and physical exam.
- The medical history may include questions about symptoms, work environment, lifestyle habits, exposure to toxins, alcohol use, risk of HIV or other infectious diseases, and family history of neurological diseases.
- The physical exam is likely to include a neurological exam to check tendon reflexes, muscle strength and tone, and the ability to sense vibration, light touch, body position, temperature, and pain.
Depending on the results of the medical history and physical/neurological exam, one or more of the following tests may be ordered:
- Nerve conduction tests – to evaluate nerve transmission and measure the degree of damage in large nerve fibers (both sensory and motor)
- Electromyography (EMG) – to detect abnormal electrical activity in muscles and help differentiate between muscle and nerve disorders
- Other nerve function tests – may include tests to record autonomic nerve function, a sweat test, and tests that record the ability to sense touch, vibration, cooling, and heat
- Nerve biopsy – to evaluate damage to nerve fibers
- Skin biopsy – to determine the number of nerve endings present and identify damage in small nerve fibers
Imaging tests, such as computed tomography (CT) scans or magnetic resonance imaging (MRI), may be performed to identify tumors, herniated discs, or other abnormalities that could be exerting pressure on nerves and causing neuropathy. See RadiologyInfo.org for more information about imaging tests.
If autonomic nerve involvement is suspected, additional testing may be performed to evaluate heart rate, blood pressure, the digestive tract, pupil response, and sweating.
Laboratory testing is used to look for underlying conditions that may cause or contribute to a neuropathy, detect complications, and evaluate organ function. Testing may include:
- Blood glucose – to detect diabetes and evaluate glucose control
- Comprehensive metabolic panel (CMP) – to evaluate liver, kidney, and other organ function; to detect metabolic problems
- Vitamin B12 – and other vitamin tests as indicated to detect vitamin deficiencies
- Thyroid panel – to detect hypothyroidism
- Cerebrospinal fluid (CSF) analysis – to detect abnormalities or infections in the central nervous system
- Specific tests for autoimmune disorders, such as antinuclear antibody (ANA)
- Specific tests for infectious conditions, such as shingles (varicella zoster virus), Lyme disease, HIV/AIDS, cytomegalovirus (CMV), Epstein-Barr virus, and syphilis
- Heavy metal tests – to detect toxin exposure
- Tests for medications such as phenytoin, long-term use of which can cause peripheral neuropathy
- Complete blood count (CBC) – to detect blood cell abnormalities, infection, and metabolic problems
- Serum protein electrophoresis (SPEP) – to rule out monoclonal gammopathy and, if indicated, followed by immunofixation electrophoresis (IFE) or an equivalent test (e.g., capillary zone electrophoresis-based immunotyping)
- Paraneoplastic antibodies, if recommended by a specialist (e.g., neurologist)
- Rarely, genetic testing to identify certain inherited disorders
Some labs offer a panel of antibody tests, such as a motor neuropathy antibody panel and a sensory neuropathy antibody panel, to aid in diagnosis. Elevations in certain antibodies have been associated with various neuropathies.