What tests are used to diagnose neuropathy? 

Diagnosing neuropathy involves a combination of electrical assessments and laboratory investigations to pinpoint exactly where and why the nerves are failing. In the United Kingdom, the diagnostic process is designed to categorize the damage as sensory, motor, or autonomic. By identifying the specific type of nerve involvement, clinicians can determine if the condition is treatable or if the focus should be on symptom management. 

Testing typically begins with non invasive bedside examinations followed by blood work to rule out systemic causes. If a diagnosis remains elusive, more specialized electrical studies are performed to measure the speed and strength of nerve signals. This article outlines the primary tests used by UK physicians like Dr. Rebecca Fernandez to evaluate peripheral neuropathy. 

What We Will Discuss In This Article 

• Blood Investigations: Identifying metabolic and nutritional triggers 

• Nerve Conduction Studies: Measuring signal velocity and amplitude 

• Electromyography: Assessing the relationship between nerves and muscles 

• Small Fibre Assessment: Tests for pain and temperature detection 

• Autonomic Testing: Evaluating involuntary nerve functions 

• Emergency guidance for rapid onset neurological symptoms 

Blood Investigations 

The first stage of testing usually involves blood panels to look for common underlying causes of nerve damage. In the UK, a standard neuropathy screen includes: 

• HbA1c: This test measures average blood sugar levels over three months and is used to identify diabetes or pre diabetes, the leading cause of neuropathy in the UK. 

• Vitamin B12 and Folate: Deficiencies in these vitamins can cause the protective myelin sheath of the nerves to degrade. 

• Kidney and Liver Function: Toxic buildup from organ failure can directly damage peripheral nerves. 

• Erythrocyte Sedimentation Rate and C Reactive Protein: These markers indicate inflammation, which may suggest an autoimmune cause. 

• Thyroid Function: An underactive thyroid can lead to fluid retention and pressure on the nerves. 

Nerve Conduction Studies (NCS) 

Nerve Conduction Studies are used to evaluate how well the large sensory and motor nerves are transmitting electrical signals. 

During this test, small electrodes are placed on the skin over a specific nerve. A tiny electrical pulse is delivered, and the equipment measures: 

• Conduction Velocity: How fast the signal travels. Slow speeds often indicate damage to the myelin. 

• Amplitude: The strength of the signal. A low amplitude suggests the axon is damaged or dying. 

Electromyography (EMG) 

An EMG is often performed alongside an NCS to assess the health of the muscles and the nerve cells that control them. 

A very thin needle electrode is inserted into a muscle. The doctor listens to and views the electrical activity of the muscle both at rest and during contraction. If a muscle is not receiving proper signals from a nerve, it will show specific patterns of electrical discharge. This test is vital for distinguishing between a primary muscle disease and nerve related weakness. 

Testing for Small Fibre Neuropathy 

Standard NCS and EMG tests only measure large nerve fibres. If you have symptoms like burning pain or loss of temperature sensation, you may have small fibre neuropathy, which requires different tests: 

• Skin Biopsy: A 3mm punch biopsy is taken from the leg to count the number of small nerve endings in the skin. 

• Quantitative Sensory Testing: A computer controlled device applies various temperatures to the skin to determine the threshold at which you feel heat, cold, or pain. 

Autonomic and Imaging Tests 

When neuropathy affects involuntary functions like heart rate or sweating, autonomic testing is required: 

• Tilt Table Test: Used to see how heart rate and blood pressure respond to changes in position. 

• Sudo scan: Measures the electrical conductance of the skin to evaluate sweat gland function. 

• MRI or CT Scans: While these do not show the nerves themselves clearly, they are used to rule out physical causes like a herniated disc or a tumour pressing on a nerve root. 

Emergency Guidance 

Certain neurological symptoms require immediate hospital evaluation to prevent permanent paralysis or respiratory failure. Seek emergency care immediately if you experience: 

• Muscle weakness that begins in the feet and spreads up toward the hips and chest over a few days 

• New difficulty swallowing, slurred speech, or drooping of the face 

• Sudden and total loss of bladder or bowel control 

• Numbness in the saddle area 

• Shortness of breath or difficulty taking a deep breath without a known cause 

In these situations, call 999 or attend your nearest Accident and Emergency department immediately. 

To Summarise 

The diagnosis of neuropathy is a comprehensive process involving blood tests to find the cause and electrical tests like NCS and EMG to map the damage. While large fibre damage is easily caught on standard equipment, small fibre neuropathy often requires more specialized techniques like skin biopsies. In the UK, these tests are essential for distinguishing between various types of nerve damage and ensuring that patients receive the correct medical intervention to slow progression and manage pain. 

Authority Snapshot 

This article was reviewed by Dr. Rebecca Fernandez, a UK trained physician with an MBBS and extensive experience in internal medicine, surgery, and emergency care. Dr. Fernandez has managed critically ill patients and stabilized acute trauma cases, providing her with a deep clinical understanding of the systemic factors that trigger neurological failure. Her background in evidence based psychiatry and digital health ensures a holistic perspective on managing both the diagnostic journey and the mental well being of those living with chronic neuropathy.