Polyneuropathy – When Many Nerves Are Affected

Tingling in the feet, numb toes, burning sensations on the soles, or an unsteady gait can be signs of polyneuropathy – a condition in which several peripheral nerves in the arms or legs are affected.

Modern diagnostic methods make it possible to assess not only the function of nerves but also their structure. In addition to classical nerve conduction studies (electroneurography, electromyography), high-resolution nerve ultrasound is becoming an increasingly important complementary tool.

What Is Polyneuropathy?

Polyneuropathy refers to a condition in which multiple peripheral nerves are impaired. “Peripheral” means that these nerves lie outside the brain and spinal cord – they carry signals that control muscles and transmit sensations such as touch, temperature, and vibration.

Common causes include:

• metabolic conditions (e.g., diabetes mellitus)
• side effects of certain medications or chemotherapy
• alcohol-related nerve damage
• vitamin deficiencies (e.g., B12)
• inflammatory or immune-mediated nerve disorders
• rarely: hereditary or other uncommon causes

It is often important to distinguish early on whether the pattern suggests a metabolic / axonal impairment or a demyelinating / inflammatory form. This distinction can guide further diagnostic steps and recommendations.

Typical Symptoms of Polyneuropathy

Symptoms often begin symmetrically and distally, most commonly in the feet (“stocking distribution”) and later possibly in the hands (“glove distribution”).

People frequently describe:

• tingling, pins-and-needles, or burning sensations in feet and toes
• numbness, unsteadiness when walking, or tripping
• pain at rest or with activity
• the feeling of “walking on cotton wool” or “on small stones”
• less commonly: weakness in foot or hand muscles

These symptoms may have many different causes — from harmless to more significant. A structured diagnostic approach helps clarify the situation.

How Are Nerves Examined Today?

Evaluation of suspected polyneuropathy usually includes several components:

Medical history and neurological examination

• characterization of symptoms
• assessment of strength, reflexes, vibration sense, and touch

Nerve conduction studies (NCS / ENG)

• measure how fast and how strongly electrical signals travel along the nerves
• can indicate whether the myelin (insulation) or the axon (nerve fiber) is mainly affected

Electromyography (EMG)

• evaluates electrical activity in muscles
• helps determine how well nerves still activate the muscles

Laboratory tests

• for example: blood sugar, vitamins, inflammatory markers, autoantibodies, depending on the situation

These methods show how well the nerves work, but they provide limited information about their structural appearance. This is where nerve ultrasound adds valuable insight.

What Is High-Resolution Nerve Ultrasound?

Nerve ultrasound uses a high-frequency ultrasound probe to visualize nerves in great detail.
Compared to conventional ultrasound, the resolution is optimized for nerves and muscles.

It can show:

• nerve size and cross-section (caliber)
• internal fascicle pattern and echogenicity
• potential compression sites (e.g., tarsal tunnel, fibular head, carpal tunnel)
• the nerve’s course and its surrounding structures

The examination is non-invasive, without radiation, and can be repeated if needed.

What Role Does Nerve Ultrasound Play in Polyneuropathy?

Polyneuropathy does not affect all nerves in the same way. The pattern of structural changes can provide helpful clues:

• Metabolic or toxic neuropathies (e.g., diabetic neuropathy) often show mild, mainly distal changes, such as at the tibial or sural nerve.
• Inflammatory neuropathies (e.g., chronic inflammatory demyelinating polyneuropathy – CIDP) may show more pronounced nerve enlargement or structural changes, sometimes extending beyond typical compression sites.

Nerve ultrasound can therefore help:

• differentiate inflammatory from non-inflammatory forms
• identify additional compression points that may contribute to symptoms
• complement inconclusive nerve conduction studies with structural information

Ultrasound does not replace nerve conduction studies or EMG — it is a useful addition.

How Is a Nerve Ultrasound Examination Performed?

The examination can be adapted to the individual situation. For polyneuropathy, nerves in the legs and arms are commonly assessed, such as:

Lower limb

• tibial nerve (popliteal fossa and medial ankle)
• peroneal nerve (fibular head)
• sural nerve (lower leg or foot)

Upper limb

• median nerve (forearm and upper arm)
• ulnar nerve (elbow and forearm)
• additional nerves depending on symptoms

Typical procedure

1. The skin over the relevant regions is exposed.
2. A small amount of gel is applied.
3. The nerves are examined in cross-section and longitudinal view.
4. Cross-sectional areas are measured and documented.
5. Any structural irregularities are captured as images or video clips.

The examination is generally well tolerated and takes about 20 to 40 minutes, depending on the scope.

What Can Nerve Ultrasound Show – and What Are Its Limitations?

Nerve ultrasound can:

• show whether nerves appear enlarged or remain within normal limits
• help determine whether distal or proximal segments are more affected
• identify additional structural factors (scarring, compression, anatomical variations)
• support differentiation between different neuropathy patterns when combined with clinical findings

Nerve ultrasound cannot:

• replace a detailed medical history or neurological examination
• replace nerve conduction studies or EMG
• measure the intensity of pain
• always show early or very mild forms — findings may be normal despite symptoms

Interpretation is therefore always performed as part of an overall assessment.

When Can a Nerve Ultrasound Examination Be Helpful?

It may be considered when:

• tingling, numbness, or pain in the feet or hands persist
• polyneuropathy is suspected and the underlying pattern should be clarified
• a coexisting compression neuropathy is possible (e.g., tarsal tunnel syndrome, fibular nerve compression, carpal tunnel syndrome)
• nerve conduction studies or EMG are inconclusive and structural information may be useful

Whether an examination is appropriate is always determined individually in a medical consultation.

Summary

Polyneuropathy is an umbrella term for conditions affecting multiple peripheral nerves. Symptoms may include tingling, numbness, burning sensations, and muscle weakness — often starting in the feet.

Diagnosis typically includes:

• medical history and physical examination
• nerve conduction studies (ENG) and EMG
• laboratory tests
• and, when appropriate, high-resolution nerve ultrasound to assess nerve structure

Nerve ultrasound can help distinguish different neuropathy patterns, identify possible compression sites, and provide a more complete understanding of the overall nerve condition.

Disclaimer: The information provided on this page is for general informational purposes only and does not constitute medical advice. It is not a substitute for personal consultation, examination, or treatment by a physician or other qualified healthcare professional. No guarantees of healing or cure are made. While we strive for accuracy and completeness, we cannot guarantee that all content is up to date or free from errors, and we accept no liability for any inaccuracies.