Diagnosing peripheral neuropathy is often difficult because its symptoms are highly variable. A thorough neurological examination is usually required that involves taking an extensive patient history, performing tests that may identify the cause of the neuropathic disorder, and conducting tests to determine the extent and type of nerve damage.
A general physical examination and related tests may reveal the presence of a systemic disease causing nerve damage. Blood tests can detect diabetes, vitamin deficiencies, liver or kidney dysfunction, other metabolic disorders, and signs of abnormal immune system activity. An examination of cerebrospinal fluid that surrounds the brain and spinal cord can reveal abnormal antibodies associated with neuropathy. On the basis of the results of the neurological examination, physical examination, patient history, and any previous screening or testing, additional testing may be ordered to help determine the nature and extent of neuropathy.
Computed tomography (CT) scan is a noninvasive, painless process used to produce rapid and clear two-dimensional images of organs, bones, and tissues. X-rays are passed through the body at various angles and are detected by a computerized scanner.
Electromyography (EMG) involves inserting a fine needle into muscles to compare the amount of electrical activity present when muscles are at rest and when they contract. EMG tests can help differentiate between muscle and nerve disorders.
A nerve biopsy is a test that involves removing and examining a sample of nerve tissue, most often from the lower leg. Although this test can provide valuable information about the degree of nerve damage, it is an invasive procedure that is difficult to perform and may cause neuropathic side effects. Many experts do not believe that a biopsy is always needed for diagnosis.
A skin biopsy is a test in which doctors remove a thin skin sample and examine nerve fiber endings. This test offers some unique advantages over nerve conduction velocity (NCV) tests and a nerve biopsy. Unlike NCV, a skin biopsy can reveal damage present in smaller fibers. In contrast to a conventional nerve biopsy, a skin biopsy is less invasive, has fewer side effects, and is easier to perform.
This answer is based on source informationfrom the National Institute of Neurological Disorders and Stroke.