How Is Neuropathy Diagnosed? Tests a Neurologist Uses

What is peripheral neuropathy and why is diagnosis important?

Peripheral neuropathy refers to damage to the nerves outside the brain and spinal cord. It can affect sensory nerves (causing numbness, tingling, or burning pain), motor nerves (causing weakness), or autonomic nerves (causing dizziness, sweating changes, or digestive symptoms) 2Ref 2National Institute of Neurological Disorders and Stroke (2023).Peripheral Neuropathy.Overview of peripheral neuropathy types, causes, diagnostic tests including NCS/EMG and skin biopsy, and differential diagnosis.

Diagnosis matters because the treatment, and more importantly the cause, varies widely. Neuropathy from diabetes looks and behaves differently from neuropathy caused by a vitamin deficiency, chemotherapy, alcohol use, an autoimmune condition, or a hereditary syndrome. Finding the cause guides both treatment and prognosis 1Ref 1Price R, Smith D, Franklin G, et al. (2022).Oral and Topical Treatment of Painful Diabetic Polyneuropathy: Practice Guideline Update Summary: Report of the AAN Guideline Subcommittee.Diabetic polyneuropathy as the most common identified cause; evidence-based treatment framework including cause identification and symptom management with duloxetine and gabapentinoids2Ref 2National Institute of Neurological Disorders and Stroke (2023).Peripheral Neuropathy.Overview of peripheral neuropathy types, causes, diagnostic tests including NCS/EMG and skin biopsy, and differential diagnosis.

What happens at the first neurologist visit?

A neurologist begins with a thorough history: when symptoms started, how they progressed, where in the body they are felt, and what makes them better or worse. Crucially, the clinician asks about diabetes, alcohol use, medications (especially chemotherapy), nutritional habits, and family history 2Ref 2National Institute of Neurological Disorders and Stroke (2023).Peripheral Neuropathy.Overview of peripheral neuropathy types, causes, diagnostic tests including NCS/EMG and skin biopsy, and differential diagnosis.

The physical examination includes:

• Testing light touch, pinprick sensation, and vibration sense in the feet and hands
• Checking reflexes (diminished reflexes are a common sign of neuropathy)
• Assessing balance and gait
• Examining muscle strength

This examination helps determine which type of nerve fibers are affected and how severe the involvement is.

What is a nerve conduction study (NCS)?

A nerve conduction study measures how fast and how strongly electrical signals travel along a nerve. Small electrodes are placed on the skin over specific nerves; a mild electrical pulse is delivered and the response recorded 3Ref 3National Library of Medicine / MedlinePlus (2024).Electromyography (EMG) and Nerve Conduction Studies.Nerve conduction studies and EMG: what they measure, conditions they diagnose (including peripheral neuropathy, carpal tunnel, Guillain-Barré, ALS), and patient experience during testing. The test assesses large nerve fibers — the ones responsible for vibration sense, proprioception (position sense), and motor function.

Results tell the neurologist:

• Whether the nerve's outer coating (myelin sheath) is damaged — causing slowed conduction velocity
• Whether the nerve fiber itself is damaged — showing reduced signal amplitude
• Which nerves are affected and how severely

NCS is generally well-tolerated; the brief electrical pulses may feel like mild static shocks 3Ref 3National Library of Medicine / MedlinePlus (2024).Electromyography (EMG) and Nerve Conduction Studies.Nerve conduction studies and EMG: what they measure, conditions they diagnose (including peripheral neuropathy, carpal tunnel, Guillain-Barré, ALS), and patient experience during testing.

What is an EMG and why is it done alongside the NCS?

Electromyography (EMG) records the electrical activity inside muscles using a thin needle electrode inserted into several muscles 3Ref 3National Library of Medicine / MedlinePlus (2024).Electromyography (EMG) and Nerve Conduction Studies.Nerve conduction studies and EMG: what they measure, conditions they diagnose (including peripheral neuropathy, carpal tunnel, Guillain-Barré, ALS), and patient experience during testing. The activity is measured at rest and during voluntary contraction. When motor nerves are damaged, muscles show abnormal electrical patterns that a neurologist can recognize.

NCS and EMG are typically done together in the same session 3Ref 3National Library of Medicine / MedlinePlus (2024).Electromyography (EMG) and Nerve Conduction Studies.Nerve conduction studies and EMG: what they measure, conditions they diagnose (including peripheral neuropathy, carpal tunnel, Guillain-Barré, ALS), and patient experience during testing. Together they give a precise picture of which nerves are affected, which muscles have lost their nerve supply, and whether the problem is in the nerve, the muscle, or the connection between them.

What blood tests are ordered for neuropathy?

Because neuropathy has many causes, blood work is essential. A standard initial panel usually includes 2Ref 2National Institute of Neurological Disorders and Stroke (2023).Peripheral Neuropathy.Overview of peripheral neuropathy types, causes, diagnostic tests including NCS/EMG and skin biopsy, and differential diagnosis:

• Fasting glucose and HbA1c (diabetes is the most common cause of peripheral neuropathy)
• Vitamin B12 level
• Thyroid function (TSH)
• Complete blood count
• Kidney and liver function
• Inflammatory markers and antibody tests if an autoimmune cause is suspected
• Serum protein electrophoresis to screen for abnormal proteins that can injure nerves

Depending on the pattern of symptoms and the NCS findings, the neurologist may add specific antibody tests (such as anti-ganglioside antibodies) or genetic testing.

What is a skin biopsy for small fiber neuropathy?

NCS only measures large nerve fibers. Small fiber neuropathy — which causes burning pain, temperature changes, and sometimes autonomic symptoms — can exist with a completely normal nerve conduction study 2Ref 2National Institute of Neurological Disorders and Stroke (2023).Peripheral Neuropathy.Overview of peripheral neuropathy types, causes, diagnostic tests including NCS/EMG and skin biopsy, and differential diagnosis. In this case, a skin punch biopsy from the leg is the most reliable way to count the density of small nerve fibers in the skin. A reduced density confirms small fiber neuropathy.

This test is typically done when symptoms are strongly suggestive of neuropathy but NCS is normal, and when other causes have been excluded.

What is the most common cause found in neuropathy workup?

Diabetes is the most frequently identified cause 1Ref 1Price R, Smith D, Franklin G, et al. (2022).Oral and Topical Treatment of Painful Diabetic Polyneuropathy: Practice Guideline Update Summary: Report of the AAN Guideline Subcommittee.Diabetic polyneuropathy as the most common identified cause; evidence-based treatment framework including cause identification and symptom management with duloxetine and gabapentinoids. A meaningful proportion of cases are labeled 'idiopathic' — meaning no definitive cause is found despite thorough workup. Even in idiopathic cases, treatment can focus on managing symptoms. The AAN guideline on painful diabetic polyneuropathy outlines evidence-based treatments for neuropathic pain that include duloxetine and gabapentinoids — approaches applicable to neuropathic pain from multiple causes 1Ref 1Price R, Smith D, Franklin G, et al. (2022).Oral and Topical Treatment of Painful Diabetic Polyneuropathy: Practice Guideline Update Summary: Report of the AAN Guideline Subcommittee.Diabetic polyneuropathy as the most common identified cause; evidence-based treatment framework including cause identification and symptom management with duloxetine and gabapentinoids.

If you have symptoms of neuropathy, a neurologist is the right specialist to see. Gale can help you understand what to expect and prepare questions for your appointment.