Understanding Nerves

What are the nerves in your body used for?

Nerves transmit signals that enable us to feel, move, and regulate certain organ functions. They connect the rest of the body to the brain and the spinal cord, the bundle of nerve tissue protected inside the spinal column. Nerve signals play a role in touch, muscle movement, and digestion, among other things.

Understanding how nerves work can help you describe your symptoms and participate in treatment decisions with your healthcare team.

What is a nerve?

A nerve is a bundle of nerve fibers that carry electrical signals. These fibers, called axons, are the extensions of nerve cells. They are enclosed in protective sheaths and supplied with blood by small blood vessels. The anatomy of nerves describes these fibers and their sheaths.

Nerves can be categorized into three types:

• Sensory nerves: Carry signals to the spinal cord or the nervous structures in the skull that provide information about touch, temperature, and danger signals (which the brain may or may not interpret as pain)
  
• Motor nerves: Transmit signals from the central nervous system to the muscles to produce movement
  
• Mixed Nerves: Combine both sensory and motor functions

Most of the body's nerves are mixed. For example, the sciatic nerve carries sensory signals from the leg to the spinal cord and motor signals from the spinal cord to the muscles. The spinal cord also exchanges signals with the brain.

What is the difference between the central and peripheral nervous systems?

The central nervous system consists of the brain and the spinal cord; the peripheral nervous system consists of the nerves and groups of nerve cells located outside these organs. The brain includes the cerebrum, the cerebellum, and the brainstem. The two parts continuously exchange signals.

Your nervous system is divided into two main parts:

The Central Nervous System (CNS) includes:

• The encephalon: the brain, the brainstem that connects it to the spinal cord, and the cerebellum, which helps coordinate movement
  
• The spinal cord

The CNS is well protected by the bones of the skull and spine. It processes information and sends commands to the rest of the body.

The Peripheral Nervous System (PNS) includes:

• 12 pairs of cranial nerves, connected to the nervous structures of the skull
  
• 31 pairs of spinal nerves, connected to the spinal cord
  
• All their branches

The PNS transmits information between your organs and the central nervous system. Its nerves travel long distances through the limbs and tissues. Some pass through bone openings or narrow tunnels, where excessive pressure can compress them.

How do nerves transmit signals?

Nerves transmit information via electrical signals that travel along their axons. Connections between nerve cells then allow these signals to be relayed throughout the nervous system.

Nerves transmit three different types of signals:

Sensory (Afferent) Signals:
These signals travel from sensory organs to nerve centers. They allow you to:

• To sense pressure and temperature, and to detect danger signals that the brain may or may not interpret as pain
  
• Perceive the position of your limbs in space
  
• Detect vibrations and textures

Motor Signals (Efferent)
These signals travel from the nerve centers to the muscles. They enable:

• Voluntary movements (walking, grasping an object)
  
• Maintaining posture
  
• Muscle coordination

Autonomic Signals
The autonomic nervous system regulates your body's automatic functions:

• The diameter of the airways, which allows more or less air to pass through
  
• Heart rate
  
• Digestion
  
• Body Temperature Regulation

These signals come together in everyday activities. When a surface is too hot, receptors—sensors located in the skin—trigger signals that reach the spinal cord. A reflex circuit—an automatic reaction—activates the muscles to pull the hand away. The brain also receives this information. This withdrawal reflex can therefore begin without waiting for a conscious decision.

What kinds of problems can affect the nerves?

Common nerve problems include nerve compression, nerve root damage, and neuropathies caused by disease or trauma. A nerve root is a group of fibers that connects the spinal cord to a nerve. Neuropathy refers to damage to the peripheral nerves. These categories may overlap.

Nerve compression

Nerve compression occurs when a nearby structure exerts excessive pressure on a nerve. The following examples involve the wrist and elbow:

Carpal Tunnel Syndrome
The median nerve is compressed at the wrist, causing numbness and tingling in the hand.

Ulnar tunnel syndrome
The ulnar nerve is compressed at the elbow. Sensations may change in the little finger and part of the ring finger, which is adjacent to it.

Radiculopathy

Radiculopathy is a disorder affecting the function of a nerve root. Compression or inflammation may contribute to it. An examination may reveal a decrease in strength, sensation, or certain reflexes—the automatic responses tested by the healthcare professional. Possible causes include:

• Herniated disc: local displacement of a portion of a disc—the cushion between two vertebrae, the bones of the spine
  
• Spinal osteoarthritis: changes in the joints between the bones of the spine
  
• Spinal stenosis: narrowing of a passageway that contains nerve structures

Pain that radiates from the back down the leg may be called sciatica. Pain that radiates from the neck down the arm may be called cervicobrachial neuralgia. These types of pain may accompany nerve damage; the path of the pain alone does not confirm a compressed nerve root. Changes in the discs, such as bulging or protrusion, are also seen in people without pain and become more common with age. A bulge affects a broad portion of the disc’s perimeter; a protrusion is a more localized displacement.¹ Osteoarthritis of the small vertebral joints may also be present without pain. A study of 191 people in Framingham observed a narrowed spinal canal in the lower back in some people without back pain, even though marked narrowing was associated with back pain in the group as a whole. Imaging findings must therefore be considered in conjunction with symptoms and physical examination.

Muscle or joint problems can mimic pain originating from a nerve root. They can also occur alongside radiculopathy. Recognizing these conditions helps in choosing the right care; many respond well to non-surgical treatments.²

Neuropathy

Neuropathy refers to damage or dysfunction of a peripheral nerve. It can affect a single nerve (mononeuropathy) or multiple nerves simultaneously (polyneuropathy).

Diabetic Neuropathy
Diabetes is a common cause of peripheral neuropathy. Prolonged high blood sugar levels can damage nerves through several mechanisms, including changes in their blood supply.^{3, 4} The feet and legs are often affected. Symptoms include tingling and loss of sensation, with or without pain. As a result, a foot injury may go unnoticed; regular medical follow-up and foot examinations are recommended.

Traumatic Neuropathy
Direct trauma can damage nerves in various ways:

• Bruises: Injuries caused by an impact
  
• Excessive stretching, such as when a shoulder is dislocated, known as a luxation
  
• Nerves partially or completely severed during fractures
  
• Compression, particularly when excessive pressure builds up within a closed muscle compartment and compresses the nerve—a condition known as compartment syndrome, which requires urgent evaluation

Neuropathy Due to Prolonged Compression
Certain occupational activities or postural habits can cause repeated compression of a nerve. For example, frequently resting on one’s elbows can compress the ulnar nerve and lead to progressive ulnar neuropathy.

Neuropathies Related to Nutrition or Body Function
A deficiency in vitamins B1, B6, or B12 can damage the nerves. Conversely, an excess of vitamin B6 from supplements can also cause neuropathy, as described in the review of nutritional neuropathies. Do not take high doses without professional advice. A blood test for vitamin B12 is part of the recommended workup when polyneuropathy—damage to multiple nerves—has no known cause.⁵ Certain medications, including chemotherapy treatments for cancer, and certain toxic substances in the workplace or environment can also damage the nerves.⁶ Excessive alcohol consumption over many years is another possible cause.⁵

How to recognize nerve damage?

Nerve damage can cause tingling, numbness, a burning sensation, or muscle weakness. Symptoms depend on which nerve fibers are affected and may appear suddenly or gradually. Pain is not always present.

The symptoms of neuropathy can occur in various combinations. The following categories are not mandatory stages:

Pain

• Radiating pain that follows the nerve's path
  
• Burning sensation or electric shock
  
• Pain that worsens with certain movements or positions

Paresthesias: tingling and unusual sensations

• Numbness
  
• Tingling (pins and needles)
  
• Feeling of "limbs falling asleep"

Changes in Strength and Sensitivity

• Muscle weakness
  
• Difficulty performing certain precise movements
  
• Reduced reflexes
  
• Loss of sensation to touch or temperature

Pain of nervous origin often radiates: it extends along the limb rather than remaining in a single spot. The path provides a clue, but not a reliable map.

In one study, 98 people had confirmed compression of the L5 nerve root and 83 had compression of the S1 nerve root—two nerve roots in the lower back. The patterns of their pain or tingling did not correspond well to the standard maps of nerve distribution. The pain’s path is therefore one clue among other findings from the examination.⁷

How does physical therapy treat nerve damage?

Physical therapy treats the effects of nerve damage through exercises, mobilizations—that is, guided movements—and modifications to daily activities. The goals include relieving certain symptoms and improving strength, movement, and the ability to perform daily tasks. Treatment varies depending on the cause; a condition such as diabetes or a significant injury also requires medical follow-up. The care of peripheral neuropathies may involve several healthcare professionals.

There are many mechanisms underlying nerve damage. Studies of spinal cords obtained after death have found associations between problems with small blood vessels, fibrosis around the nerve roots, and changes in nerve fibers. Fibrosis refers to an accumulation of fibrous tissue, similar to scar tissue. These observations help us understand the disease; they do not identify the primary mechanism in every individual.⁸

Reducing Pressure on the Nerve

When pressure contributes to symptoms, treatment aims to reduce it or prevent it from continuing:

• Adjusting Positions: Identify positions that worsen symptoms or put pressure on the nerve, then explore other options
  
• Adapting Tools and the Workstation: Adjustments to the workstation, the home environment, or sports equipment
  
• Positioning Techniques: Teaching resting positions that minimize tension on the nerve
  
• Targeted muscle strengthening: Exercises designed to improve strength and movement control, such as those for the neck and shoulders

Circulation and Swelling Management

Nerves need blood to receive oxygen and nutrients. After certain injuries, swelling can also interfere with movement. Rehabilitation following a nerve injury—the care that helps restore movement and daily activities—may include the following measures, depending on the assessment:

• Joint mobilization: Movements guided by the physical therapist's hands to treat a stiff joint
  
• Appropriate endurance exercises: Walking, biking, or other activities that get your heart and lungs working
  
• Swelling Management: Movements and positions chosen to aid fluid drainage, when appropriate for the injury
  
• Relaxation Techniques: Slow Breathing and Relaxation to Reduce Tension and Make Daily Activities Easier

Restoring Nerve Mobility

Nerves normally move relative to the surrounding tissues. If certain movements are restricted or painful, the physical therapist may recommend:

• Nerve-sliding techniques: Movements that slide the nerve relative to the surrounding tissues, depending on your tolerance
  
• Mobilization of adjacent tissues: Guided movements of adjacent tissues and joints (muscles, fascia, fibrous sheaths, and joints) through which the nerve travels
  
• Progressive exercises: Gradual increase in range of motion based on symptoms

Pain Management and Education

Nerve pain can be particularly debilitating and difficult to understand:

• Explanations About Nerves and Pain: Understanding Symptoms and Treatment Options Helps You Choose Appropriate Activities
  
• Coping Strategies: Techniques to maintain daily activities despite symptoms
  
• Progressive rehabilitation: Gradual restoration of tolerated sensations or movements, with the pace of progress adjusted by the professional
  
• Relaxation Techniques: Managing stress that can amplify pain perception

Healing Timeline

Some peripheral nerve fibers can regrow after an injury. When regrowth is necessary, it often progresses at a rate of about one millimeter per day, following an initial repair phase. Follow-up after repair of an arm nerve describes this benchmark and its limitations. Over long distances, recovery can take months or years and may remain incomplete. A simple, temporary disruption of conduction—the transmission of signals—may follow a different course.

After an injury, the nervous system can become more sensitive. Changes can affect not only the peripheral nerves but also the circuits in the spinal cord and brain. Persistent pain is real; its intensity does not simply reflect the remaining compression.⁹ A study of genetic factors—related to inherited biological information—found an association between a variation in the KCNS1 gene and pain in five of the six patient groups studied. This finding illustrates some of the differences between individuals, without determining your own course of recovery.¹⁰

Nerve recovery can take a long time and requires regular follow-up. It cannot be directly compared to the recovery of tendons, which connect muscles to bones, or ligaments, which connect bones to one another. These tissues have different functions and are subject to different types of injuries. The program takes into account the injury, the movements you have regained, and the activities that are important to you. A severe injury may require surgery; in such cases, physical therapy complements the guidelines for protection and recovery.

What is Neural Gliding?

Nerve gliding is a mobilization technique that combines movements to slide a nerve relative to the surrounding tissues. The physical therapist can guide these movements or teach you how to do them yourself.

Two Types of Nerve Mobility

Intraneural mobility: The fibers and small bundles move relative to one another within the nerve.
Extraneural mobility: The nerve moves relative to the surrounding tissues.

An injury or compression can alter this mobility and make certain movements more painful. Adhesions—fibrous bands between tissues—or inflammation can contribute to this. Pain alone is not enough to determine which of these changes is present.

Neural gliding techniques

Glide These movements place tension on one part of the nerve pathway while releasing tension from another part. The nerve thus moves with less of an increase in tension than with a tensioning technique. Possible mechanisms include:

• Changes in blood flow around the nerve, which are still being studied as a possible mechanism
  
• Changes in inflammatory responses, with some of the data coming from experimental models
  
• A redistribution of the fluid accumulated in the nerve, known as edema dispersion
  
• A change in the relationship between tissues, with no evidence that the technique removes adhesions in every patient

Tensioning This technique involves a controlled increase in tension along the nerve pathway. The physical therapist selects the positions and range of motion based on your evaluation. Possible goals include:

• Gradually build up your ability to tolerate stress
  
• Improving tolerance to movement
  
• Reduce excessive sensitivity to certain movements or pressure

Findings Regarding the Nerve and Symptoms

A review of four studies involving 45 postmortem bodies observed better dispersion of a liquid injected into the nerves following mobilization techniques. This laboratory finding does not directly measure pain or drainage in a person undergoing treatment. However, a 2024 clinical review found a short-term improvement in conduction velocity—the speed of nerve signals—particularly in the carpal tunnel. The confidence in the findings regarding signals to the muscles was moderate. It was very low for signals related to sensation. Some measures of nerve size also showed improvement, though the evidence was very uncertain; other measures of conduction showed no clear difference.

A 2017 review of 40 studies reported improvements in pain and daily functioning for certain types of chronic lower back pain, as well as improvements in chronic pain extending from the neck to the arm. “Chronic” here means that the pain has persisted for several months. For carpal tunnel syndrome, this review found no benefit on most clinical measures, despite some favorable results regarding nerve function. The effect remained uncertain for tennis elbow, cubital tunnel syndrome, and following lumbar surgery.¹¹

The evidence has evolved. A 2023 review of mild to moderate carpal tunnel syndrome included 12 trials and 1,003 participants. It reported improvements in symptoms, activities, and pain with these techniques, but no clear difference in grip strength—the force used to squeeze an object. The studies show significant differences and some risks of bias, limitations that may influence their results. For low back pain with leg pain related to a nerve root, another review of eight trials observed possible short-term benefits. Six of the eight trials favored adding mobilization techniques to the comparator treatment; the results of the other two were inconclusive. The choice therefore depends on the specific condition being evaluated:

• Carpal Tunnel Syndrome
  
• Lower back pain associated with pain originating from a nerve root
  
• Cervicobrachial neuralgia
  
• Lateral epicondylitis, tendon pain on the outer side of the elbow
  
• Sciatica

The physical therapist assesses symptoms, strength, sensitivity, and response to movement. Tension tests serve as indicators; they do not directly measure all of the nerve’s internal structures. Mobilization techniques are progressed based on your tolerance. An exercise that worsens symptoms or reveals weakness requires adjustment and reevaluation.

How to prevent nerve problems?

Preventing nerve problems involves reducing prolonged stress, protecting against injuries, and managing conditions such as diabetes. Appropriate physical activity and a balanced diet also support overall health. These measures reduce certain risks but do not prevent all cases of neuropathy.

Ergonomics and posture at work

Certain positions can increase pressure on a nerve, especially if held for a long time. Adjust your workstation so that you're comfortable and can change positions:

• Adjust your screen so you can look straight ahead without straining your neck
  
• Adjust the forearm support so that it does not press too hard against your wrists or elbows
  
• Change the position of your legs if you keep them crossed for a long time; pressure near the outer side of the knee can irritate the peroneal nerve, which controls certain movements of the foot
  
• Regularly alternate between sitting and standing positions if possible

A study of office workers compared ergonomics training, training combined with an adjustable chair, and a control group that received neither of these interventions. Ergonomics involves adapting tools and the workstation to the individual. Both groups that received training improved their knowledge and habits, with fewer risk factors observed for muscles and joints. This study did not directly measure the prevention of nerve compression.¹²

Mobility and Regular Exercise

Nerves move with the body's movements. To stay active while managing a nerve condition, you can:

• Incorporate gentle stretches into your daily routine
  
• Change positions regularly
  
• Explore the range of motion you can tolerate, then gradually increase it
  
• Maintain a regular exercise routine that is appropriate for your health condition

Diabetes, Diet, and Lifestyle Habits

Certain medical conditions and lifestyle habits can increase the risk of nerve damage. Your care team will help you decide on a monitoring plan:

• Diabetes Management: Controlling blood sugar helps prevent or slow the progression of certain types of neuropathy, especially in type 1 diabetes. A study followed 1,172 people with this type of diabetes for about seven years. The onset of neuropathy was associated with average blood sugar levels, duration of diabetes, weight relative to height, and smoking, after adjusting for other factors. Blood pressure and blood lipids were also associated with the risk in some analyses.¹³ Treatment goals remain individualized.
  
• Nutrition: Prevent deficiencies—particularly in vitamin B12—with advice tailored to your diet and health concerns
  
• Limit Alcohol: Excessive alcohol consumption can damage peripheral nerves
  
• Hydration: Drink according to your needs and any applicable medical advice

Protection Against Injuries

During risky activities:

• Wear appropriate protective gear (knee pads, elbow pads)
  
• Adapt your movements and positions to the demands of the activity and your level of preparation
  
• Warm up before intense physical activities
  
• Gradually increase your workout intensity to avoid overexertion

Early Symptom Recognition

An evaluation helps identify the cause and determine the appropriate treatment. See a doctor if you notice the following symptoms, and seek medical advice promptly if you experience new or worsening weakness:

• Recurrent numbness or tingling
  
• Progressive muscle weakness
  
• Pain that radiates along a limb
  
• Symptoms that persist for more than a few days

When to consult a physiotherapist?

Physical therapy is recommended when persistent neurological symptoms interfere with your movement or daily activities, after ruling out any signs that require urgent medical attention. The physical therapist will assess your condition and refer you to a doctor if necessary.

Consult a physiotherapist if you experience:

• Radiating pain that follows a specific path (arm, leg)
  
• Persistent numbness or tingling
  
• Progressive muscle weakness
  
• Pain that worsens with certain positions or movements
  
• Symptoms that interfere with your daily activities

Any new or worsening weakness warrants prompt medical attention. An early evaluation helps identify causes that require specific treatment, though it does not guarantee that the symptoms will disappear completely.

Go to the emergency room immediately if you experience pain that starts in your lower back and radiates down both legs. Significant weakness or numbness in both legs—or if these symptoms worsen—also requires immediate evaluation. A loss of sensation around the genitals or anus, a new difficulty starting to urinate, an inability to urinate, a new loss of bladder or bowel control, or no longer feeling the urge to have a bowel movement also require immediate evaluation. These warning signs may indicate severe nerve compression in the lower back. No single sign is sufficient on its own to confirm or rule out this problem.¹⁴

References

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1. Brinjikji W, Luetmer PH, Comstock B, Bresnahan BW, Chen LE, Deyo RA, et al. Systematic literature review of imaging features of spinal degeneration in asymptomatic populations. AJNR Am J Neuroradiol. 2015;36(4):811-6. (Back to section: 1)
2. Lauder TD. Musculoskeletal disorders that frequently mimic radiculopathy. Phys Med Rehabil Clin N Am. 2002;13(3):469-85. (Back to section: 1)
3. Yagihashi S, Mizukami H, Sugimoto K. Mechanism of diabetic neuropathy: Where are we now and where do we go from here? J Diabetes Investig. 2011;2(1):18-32. (Back to section: 1)
4. Pop-Busui R, Boulton AJ, Feldman EL, Bril V, Freeman R, Malik RA, et al. Diabetic Neuropathy: A Position Statement by the American Diabetes Association. Diabetes Care. 2017;40(1):136-154. (Back to section: 1)
5. Callaghan BC, Price RS, Feldman EL. Distal Symmetric Polyneuropathy: A Review. JAMA. 2015;314(20):2172-81. (Back to sections: 1, 2)
6. Toledano, M. "Toxin-Induced Neuropathies." *Neurol Clin*. 2020;38(4):749-763. (Back to section: 1)
7. Taylor CS, Coxon AJ, Watson PC, Greenough CG. Do L5 and S1 nerve root compressions produce radicular pain in a dermatomal pattern? Spine (Phila Pa 1976). 2013;38(12):995-8. (Back to section: 1)
8. Jayson MI. The role of vascular damage and fibrosis in the pathogenesis of nerve root damage. Clin Orthop Relat Res. 1992(279):40-8. (Back to section: 1)
9. Fornasari, D. Pain mechanisms in patients with chronic pain. Clin Drug Investig. 2012;32 Suppl 1:45-52. (Back to section: 1)
10. Costigan M, Belfer I, Griffin RS, Dai F, Barrett LB, Coppola G, et al. Multiple chronic pain conditions are associated with a common amino acid-substituting allele in KCNS1. Brain. 2010;133(9):2519-27. (Back to section: 1)
11. Basson A, Olivier B, Ellis R, Coppieters M, Stewart A, Mudzi W. The Effectiveness of Neural Mobilization for Neuromusculoskeletal Conditions: A Systematic Review and Meta-analysis. J Orthop Sports Phys Ther. 2017;47(9):593-615. (Back to section 1)
12. Robertson M, Amick BC, DeRango K, Rooney T, Bazzani L, Harrist R, et al. The effects of an office ergonomics training and chair intervention on worker knowledge, behavior, and musculoskeletal risk. Appl Ergon. 2009;40(1):124-35. (Back to section: 1)
13. Tesfaye S, Chaturvedi N, Eaton SE, Ward JD, Manes C, Ionescu-Tirgoviste C, et al. Vascular risk factors and diabetic neuropathy. N Engl J Med. 2005;352(4):341-50. (Back to section: 1)
14. Fairbank J, Hashimoto R, Dailey A, Patel AA, Dettori JR. Does the patient’s history and physical examination predict MRI-confirmed cauda equina syndrome? Evid Based Spine Care J. 2011;2(4):27-33. (Back to section: 1)
15. Gordon T. The role of neurotrophic factors in nerve regeneration. Neurosurg Focus. 2009;26(2):E3.

What should you know about nerves?

Nerves transmit the signals necessary for sensation, movement, and various automatic functions. Damage to the nerves can affect sensation, strength, or organ function, with or without pain. The examination identifies the cause and its consequences to determine the appropriate treatment.

Physical therapy can improve movement, daily activities, and certain nerve-related symptoms. Neural mobilization offers benefits for several specific conditions, although the degree of effectiveness varies across studies. Medical follow-up remains necessary for certain causes and for urgent symptoms.