Peripheral Nerve

What is peripheral nerve?

A peripheral nerve is any nerve that lies outside the brain and spinal cord. Together, these nerves make up the peripheral nervous system, the network of cables that carries messages between the central nervous system (the brain and spinal cord) and the rest of the body. Some peripheral nerves carry sensation such as touch, temperature and pain. Others carry movement signals to muscles. A third group, called autonomic nerves, controls automatic functions such as heart rate, blood pressure, sweating, digestion and bladder control.

When people search for “what is peripheral nerve,” they are usually asking about problems that affect these nerves. Doctors group these problems under the term peripheral nerve disorders. The most common is peripheral neuropathy, which means damage to peripheral nerves that leads to numbness, tingling, pain or weakness. Damage may involve a single nerve (mononeuropathy, for example carpal tunnel syndrome), several separate nerves (mononeuritis multiplex) or many nerves throughout the body at the same time (polyneuropathy). Peripheral nerves can also be injured by cuts, stretching, crushing or pressure.

Peripheral nerve disorders can affect people of any age, but they become more common with advancing age. People living with diabetes, those who drink alcohol heavily, people receiving certain cancer treatments and people with some inherited conditions are affected more often. In many hospitals, including Acibadem, peripheral nerve disorders are managed mainly by the Neurology department, often working alongside other specialists when surgery or rehabilitation is needed.

Peripheral nerve symptoms

Peripheral nerve symptoms depend on which type of nerve fibers are damaged, how many nerves are involved and how quickly the damage develops. Sensory nerve damage tends to cause abnormal feelings, motor nerve damage tends to cause weakness, and autonomic nerve damage affects body functions that normally happen without conscious effort.

• Numbness or reduced feeling, often beginning in the toes and feet and sometimes spreading upward
• Tingling or a “pins and needles” sensation
• Burning, stabbing or electric shock-like pain, which may be worse at night
• Increased sensitivity to touch, so that light contact such as bedsheets feels painful
• Muscle weakness in the hands, feet, arms or legs
• Loss of balance or coordination, especially in the dark or on uneven ground
• Muscle cramps, twitching or wasting (loss of muscle bulk)
• Dizziness on standing, caused by changes in blood pressure control
• Digestive, bladder or sexual problems, or abnormal sweating
• Foot problems such as ulcers or unnoticed injuries because pain signals are lost

In polyneuropathy, symptoms usually appear on both sides of the body and follow a “stocking and glove” pattern, starting at the tips of the toes and fingers because the longest nerve fibers are affected first. In a mononeuropathy, symptoms are limited to the area supplied by one nerve. For example, pressure on the median nerve at the wrist typically causes numbness in the thumb, index and middle fingers, while pressure on the peroneal nerve near the knee may cause difficulty lifting the foot.

Symptoms also differ by stage. Early on, many people notice only occasional tingling or a slight change in sensation. As nerve damage progresses, numbness may become constant, pain may develop, and weakness or balance problems may appear. Some conditions, such as Guillain-Barré syndrome (a rare immune disorder that attacks peripheral nerves), develop over days to weeks and can become serious quickly, while others progress slowly over many years.

Causes and risk factors

There are many peripheral nerve causes, and in a proportion of people no specific cause is found even after careful testing. This is called idiopathic neuropathy. Known causes include:

• Diabetes, the most common cause of polyneuropathy in many countries; high blood sugar over time damages small blood vessels that supply the nerves
• Physical injury, such as fractures, deep cuts, crush injuries, stretching during a fall or accident, or repeated pressure on a nerve
• Nerve entrapment, where a nerve is squeezed as it passes through a narrow space, as in carpal tunnel syndrome or cubital tunnel syndrome at the elbow
• Vitamin deficiencies, particularly vitamin B12, and sometimes other B vitamins or vitamin E
• Heavy alcohol use, which affects nerves directly and contributes to poor nutrition
• Medications and toxins, including some chemotherapy drugs, certain antibiotics and exposure to heavy metals or industrial chemicals
• Infections, such as shingles, HIV, hepatitis C, Lyme disease and leprosy
• Autoimmune and inflammatory conditions, including Guillain-Barré syndrome, chronic inflammatory demyelinating polyneuropathy (CIDP), lupus, rheumatoid arthritis and vasculitis (inflammation of blood vessels)
• Kidney disease, liver disease and thyroid disorders
• Inherited conditions, such as Charcot-Marie-Tooth disease, in which faulty genes affect nerve structure
• Tumors, which may press on a nerve or, rarely, grow from the nerve itself

Risk factors overlap with these causes. You may be more likely to develop a peripheral nerve disorder if you have diabetes that is poorly controlled, are older, have a family history of neuropathy, drink alcohol heavily, have kidney or liver disease, have received chemotherapy, or do work or hobbies involving repetitive movements or prolonged pressure on a nerve. Obesity and smoking are also associated with a higher risk, partly because they affect blood flow to the nerves.

Diagnosis

Peripheral nerve diagnosis begins with a detailed conversation about your symptoms, when they started, how they have changed, your medical history, medications, alcohol use, occupation and family history. Your doctor will then examine you, testing sensation with light touch, pinprick, vibration and temperature, checking muscle strength and reflexes, and observing your walking and balance. This examination often points toward whether one nerve or many nerves are involved and whether sensory, motor or autonomic fibers are affected.

Tests are then chosen to confirm the problem and look for a cause:

• Blood tests to check blood sugar, vitamin B12 and other vitamin levels, kidney, liver and thyroid function, and markers of inflammation or infection
• Nerve conduction studies, in which small electrical pulses are delivered to a nerve through the skin and the speed and strength of the signal are measured; slowed or weak signals indicate nerve damage and help show its pattern
• Electromyography (EMG), in which a fine needle records electrical activity inside muscles to show whether the nerve supplying them is working normally
• Imaging, such as ultrasound or magnetic resonance imaging (MRI), to look for a nerve that is compressed, swollen, injured or affected by a tumor
• Autonomic testing, which measures heart rate and blood pressure responses, sweating and other automatic functions
• Skin biopsy, removing a tiny sample of skin to count small nerve fibers when small-fiber neuropathy is suspected
• Nerve biopsy, removing a small piece of nerve for microscopic examination; this is done only in selected cases because it can leave permanent numbness
• Lumbar puncture (spinal tap), sometimes used when an inflammatory or infectious cause such as Guillain-Barré syndrome is suspected
• Genetic testing when an inherited neuropathy is a possibility

There is no single test that confirms every peripheral nerve disorder. Instead, doctors combine the pattern of symptoms, examination findings and test results to reach a diagnosis and, where possible, identify a treatable cause.

Treatment options

Peripheral nerve treatment options depend on the cause, the type and severity of nerve damage, and how much symptoms affect daily life. Treatment usually has two goals: addressing the underlying cause to prevent further damage, and relieving symptoms.

Treating the cause. When a cause is found, managing it is the most important step. This may mean improving blood sugar control in diabetes, replacing a deficient vitamin, stopping or changing a medication that is harming nerves, treating an infection, reducing or stopping alcohol, or using immune-suppressing treatments for autoimmune neuropathies. Peripheral nerves can regrow slowly, so removing the cause may allow gradual improvement in some cases, although recovery is not always complete.

Observation. Mild symptoms, or a mild entrapment that is not worsening, are sometimes simply monitored, with advice on protecting the nerve, changing activities and checking for progression at follow-up visits.

Medication for symptoms. Ordinary painkillers often help little with nerve pain. Doctors more commonly use medicines originally developed for epilepsy or depression that calm overactive nerve signals, such as gabapentin, pregabalin, duloxetine or amitriptyline. Topical treatments such as lidocaine patches or capsaicin cream may be used for localized pain. Stronger pain medicines are generally used cautiously and for limited periods. Medications for dizziness, bowel, bladder or sweating problems may be prescribed for autonomic symptoms. All of these medicines have possible side effects, and finding the right one at the right dose may take time.

Procedures. For an entrapped nerve, a steroid injection near the nerve may reduce swelling and relieve symptoms for a period. Splints or braces can rest a compressed nerve, for example a wrist splint worn at night for carpal tunnel syndrome. Nerve blocks, transcutaneous electrical nerve stimulation (TENS, a device that delivers mild electrical pulses through the skin) and, in selected cases, implanted stimulators may be considered for difficult pain.

Surgery. Surgery may be recommended when a nerve is being compressed and non-surgical measures have not worked, when a nerve has been cut or badly injured, or when a tumor is pressing on a nerve. Operations include releasing the tissue that is squeezing a nerve (decompression), repairing a cut nerve by stitching the ends together, bridging a gap with a nerve graft taken from elsewhere in the body, or nerve transfer, in which a less important working nerve is rerouted to restore function. Nerve fibers regrow slowly, and recovery after repair can take many months and may remain incomplete.

Rehabilitation. Physical therapy helps maintain strength, flexibility and balance, and reduces the risk of falls. Occupational therapy teaches ways to manage daily tasks safely when hands or feet are numb or weak. Braces, special footwear and walking aids may be recommended. People with numb feet are usually advised to inspect their feet daily and to have regular foot checks, because unnoticed injuries can become serious.

Living with peripheral nerve disorders and outlook

The outlook varies widely. Some peripheral nerve problems, such as a mild pressure injury or a vitamin deficiency that is corrected early, may improve considerably or resolve. Others, such as diabetic neuropathy or inherited neuropathies, are usually long-term conditions in which the aim is to slow progression and manage symptoms rather than to cure. Nerves regenerate slowly, at roughly a millimeter or so per day under favorable conditions, so improvement after an injury or treatment can take months and is not guaranteed.

Many people find that day-to-day life is easier when they keep blood sugar and blood pressure within target ranges, avoid alcohol, stay physically active within safe limits, protect numb areas from injury and heat, wear well-fitting shoes, remove tripping hazards at home and use good lighting at night. Nerve pain can affect sleep and mood, and it is reasonable to discuss these effects with your care team; support for sleep and mental health is part of managing a chronic condition. Regular follow-up allows treatment to be adjusted as symptoms change.

Frequently asked questions

What is peripheral nerve damage and is it the same as neuropathy?

Peripheral nerve damage means that nerves outside the brain and spinal cord have been injured or are not working properly. Neuropathy is the medical term for this, so the two phrases are often used interchangeably. Doctors may add words to describe the pattern, such as polyneuropathy when many nerves are involved or mononeuropathy when a single nerve is affected.

What are the first peripheral nerve symptoms people usually notice?

Early peripheral nerve symptoms are often subtle: occasional tingling, a feeling of wearing an invisible sock, mild numbness in the toes or fingertips, or burning that is more noticeable at night. Because these signs can have many explanations, they are worth mentioning to a doctor, particularly if they persist, spread or are accompanied by weakness.

What are the most common peripheral nerve causes?

In many parts of the world diabetes is the single most common cause of polyneuropathy. Other frequent peripheral nerve causes include physical injury, nerve entrapment such as carpal tunnel syndrome, vitamin B12 deficiency, heavy alcohol use, certain medications including some chemotherapy drugs, infections and autoimmune conditions. In a proportion of people, no cause is identified despite thorough testing.

How is peripheral nerve diagnosis confirmed?

Peripheral nerve diagnosis relies on a combination of your symptom history, a neurological examination and targeted tests. Nerve conduction studies and electromyography are the main tests for confirming nerve damage and showing its pattern, while blood tests, imaging and occasionally biopsies are used to look for the cause. Your doctor selects tests based on your individual situation rather than ordering every test for everyone.

What peripheral nerve treatment options are available if the damage is permanent?

Even when nerve damage cannot be reversed, treatment can still help. Options include medicines that reduce nerve pain, physical and occupational therapy to preserve function and prevent falls, braces or footwear to support weak limbs, and careful foot care to avoid injuries. Managing the underlying cause remains important to limit further damage.

Can peripheral nerves heal on their own?

Peripheral nerves have some ability to regrow, unlike nerves in the brain and spinal cord. Whether and how fully a nerve recovers depends on the type and severity of the damage, how long it has been present, the person’s age and general health, and whether the cause has been removed. Recovery is slow and may be partial, so realistic expectations and follow-up with your care team are important.

Which doctor treats peripheral nerve problems?

Neurologists, doctors who specialize in the nervous system, usually lead the diagnosis and medical management of peripheral nerve disorders. Depending on the cause, other specialists may be involved, including endocrinologists for diabetes, hand or plastic surgeons and neurosurgeons for nerve repair or decompression, pain specialists, and physical therapists for rehabilitation.

When to see a doctor

Persistent numbness, tingling, burning pain or weakness in the hands or feet should be assessed by a doctor, even if the symptoms seem mild, because early identification of a cause such as diabetes or a vitamin deficiency can limit further damage. Seek urgent medical attention if you notice any of the following:

• Weakness that spreads rapidly over hours or days, especially if it moves from the legs upward
• Difficulty breathing, swallowing or speaking
• Sudden loss of bladder or bowel control
• Numbness or weakness after an injury, deep cut or fracture
• Sudden numbness or weakness on one side of the body, facial drooping or confusion, which may signal a stroke rather than a peripheral nerve problem and needs emergency care
• A foot wound, ulcer or infection in a numb foot, particularly if you have diabetes
• Severe dizziness or fainting on standing
• Symptoms that begin during or shortly after starting a new medication, including chemotherapy

If your symptoms are gradual and stable, a routine appointment is usually appropriate, but any sudden change or rapid worsening should be treated as a medical emergency.