Peripheral Neuropathy & Treatments

Peripheral Neuropathy Diagnosis

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One or two symptoms of neuropathy do not necessarily mean that someone has neuropathy. In fact, there are many different indicators that guide a doctor's diagnosis. During a physical exam, a doctor uses the symptoms, signs, and test results to provide patients with an accurate diagnosis.

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In addition, a doctor will need to rule out other possible diagnoses, such as Guillain-Barre syndrome or a disease of the neuromuscular junction. This is especially true when the symptoms came on suddenly or the neurological symptoms got worse quickly.

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How is neuropathy diagnosed?

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To diagnose small fiber neuropathy, the first step is to get a physical exam done by a physician. Based on your symptoms, medical history, family history, and physical exam findings, the doctor may determine the underlying cause of your symptoms. There are a few kinds of tests that can be done to confirm the diagnosis, depending on the underlying cause of neuropathy.

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Skin Biopsy to Diagnose Peripheral Neuropathy

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A definitive diagnosis can be made by doing a biopsy of the skin. A 3mm piece of skin on the calf, thigh, or arm is removed and sent to a pathologist. The pathologist looks at the skin under a microscope and counts the number of blood vessels and nerves in the sample of skin. The good news is that a biopsy is usually only necessary if there the diagnosis is uncertain.

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A skin biopsy looks at a specific kind of nerve called unmyelinated nerve fibers. Unmyelinated nerve fibers are small nerves that does not have a protective covering known as a myelin sheath. These nerve fibers are small and superficial, providing sensation to the skin.

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A skin biopsy may be needed to diagnose small fiber neuropathy in the earliest stages of the disease course. Early in the course of neuropathy, before the disease has progressed, other tests such as nerve conduction studies may be normal. Skin biopsy is a useful diagnostic tool when the diagnosis of neuropathy is unclear. 

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Electrodiagnostic Testing to Diagnose Peripheral Neuropathy

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Electrodiagnostic testing is typically recommended when the reason why someone has peripheral neuropathy is unclear. For example, if you are a diabetic, numbness in only one foot is indicative that it is unlikely that diabetic neuropathy is the reason for the numbness. It may indicate a nerve entrapment syndrome like sciatica and the treatment would be much different.

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A quick note about nerve conduction studies (NCS) and electromyography (EMG) - these two tests are useful diagnostic tools for large fiber neuropathy, but frequently are not as helpful in diagnosing small fiber neuropathy. Many people with neuropathic pain symptoms have had these tests done by a neurologist. So although you may have had these tests done (NCS/EMG) and those test results are normal, a diagnosis of small fiber neuropathy is not necessarily excluded. Large fiber neuropathy and other nerve issues have different causes and typically require different treatments.

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Autonomic Testing to Diagnose Peripheral Neuropathy

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Autonomic testing involves a series of tests in order to identify potential damage to the autonomic nervous system. The autonomic nervous system is the part of the nervous system that is responsible to bodily functions that happen regardless of whether we want it to. For example, breathing, the heart rate, and sweating are all controlled by the autonomic nervous system.

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Examples of autonomic testing include a tilt-table test, orthostatic blood pressure measurements, heart rate variability, and the quantitative sudomotor axon reflex test. When these tests are conducted, the results are compiled into a scoring system known as the composite autonomic scoring system (CASS). Autonomic testing can help to verify a diagnosis of small fiber neuropathy.

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Nerve Biopsy to Diagnose Peripheral Neuropathy

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Nerve biopsy is an invasive surgical procedure that is sometimes needed to diagnose certain types of neuropathies, such as amyloid neuropathy or vasculitis.

• Amyloid neuropathy is a disease where the body forms a specific kind of protein known as amyloid protein. In amyloid neuropathy, this protein is deposited in the nerves, resulting in damage and poor function of the nerve.

• Vasculitis refers to diseases that involve inflammation of the blood vessels. The inflammation of the blood vessels causes the body's immune system to attack and destroy the blood vessels. As a result, there are few blood vessels to provide oxygen and nutrition to the nerves. Without oxygen and nutrients, the nerves become damaged and die.

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Nerve biopsies are not common and the diseases biopsies seek to diagnose are just as uncommon. If a biopsy is done, the doctor will likely sample a nerve located on the calf muscle called the sural nerve. Biopsy of the sural nerve leaves a small scar from a single incision.