Unexplained Nerve Pain in Foot - Causes, Symptoms & Treatment | Pain Care

Unexplained Nerve Pain in Foot – Causes, Symptoms & Treatment

Peripheral nerves (sensory, motor and autonomic) are important for the proper functioning of the body. Numbness or weakness in the body is caused when these nerves stop sending messages, while incorrect signals lead to pain.

Nerve pain progression is usually retrograde – commencing far from the brain and spinal cord at hands or feet and moving towards the arms and legs. It is possible to reverse the progression in some cases or halt it by treating the root cause.

Nerve pain in the foot is often described as burning, cramps and numbness sensations. The key questions needed to assess and treat nerve pain in the foot are the type of pain, duration and the resulting changes in lifestyle. As medication induced neuropathy is common, intake of vitamins or supplements along with their doses also need to be considered.

Peripheral neuropathy can be caused by a damage to the axons or demyelination (a damage to the myelin sheath insulating the axon).

Nerve pain in the foot can also be a result of a problem in the lower spine.

Causes of Nerve Pain in Foot

Diabetes

DiabetesThe most likely cause of neuropathy in the foot is diabetes. Reports indicate neuropathy in around 60% to 70% of people with diabetes [1].

High blood glucose is one of the factors causing nerve damage. The symptoms are found to become worse at night.

In sufferers, legs and feet are more likely to be affected before hands and arms causing symptoms such as sharp pains or cramps, a tingling, burning, or prickling sensation, numbness or insensitivity to pain or temperature. Early symptoms can get better with the regulation of blood sugar.

Uncontrolled diabetes could lead to damaged nerves resulting in insensitivity to pain, heat or cold. Pain usually serves as a warning, for eg. nerves send a signal to the brain when your hand gets too close to the fire. When nerves are damaged, the system stops working making you prone to injuries.

It is extremely important to take care of the feet for diabetics as reports suggest 80% of the over 7,000 amputations a year in England alone related to diabetes could be prevented. [2]

Feet should be checked for calluses, cuts or blisters. Sufferers should wear soft and loose cotton socks. If the foot is sensitive to heat or cold, a padding can be used to cover the feet from the bedcovers while sleeping. Monitoring of blood glucose levels is imperative, as a controlled blood glucose level might improve the nerve pain in the foot.

Medicine-induced Neuropathy

Drug-induced peripheral neuropathy can be noticed weeks to months post medication and reach a peak at the end of the treatment.

In most cases, identifying the particular drug and stopping treatment resolves the pain. The toxic effect of some of the drugs could result in damage to the axon part of the nerve cell thereby interfering with the signals.

Symptoms usually include weakness, with sensation changes commencing at the outer parts of the body and moving towards the center of the body. [3]

Drug-induced peripheral nerve damage is quite common in patients receiving chemotherapy. The chemotherapeutic agent vincristine is a known neurotoxic.

Paraesthesia, which is a tingling or pricking sensation, has been found to be a result of vincristine-induced peripheral neuropathy. Paclitaxel, oxaliplatin, docetaxel and arsenic trioxide are some of the other highly toxic chemotherapy drugs.

Several drugs treating HIV have also been found to be potential peripheral neuropathy inducers.

Antimycobacterial agents to treat tuberculosis have been found to be potential peripheral neuropathy inducers.

In particular, studies indicate isoniazide as a cause for reversible peripheral neuropathy. Other potential inducers include drugs used in the treatment of the following

  • Heart diseases and high blood pressure
  • Autoimmune diseases
  • Seizures
  • Alcoholism
  • Gout with colchicine [4,5,6]

Drug-induced neuropathy can be remedied by discontinuing the drug or changing the dose. However, it might take several months for the pain to resolve. Although, in rare cases, nerve damage is seen to be permanent.

Injury

Physical injury, which is the most common cause of acquired nerve injury, can be categorized into sudden trauma and repetitive stress.

Nerves can get severed, compressed or crushed because of injury during activities such as sports-related, surgical procedures or other accidents. Pressure from broken or dislocated bones can also damage nerves.

Entrapment neuropathies are caused by repetitive stress. The breakdown of the blood-nerve barrier is a result of compression of any nerve, over time. Nerve compression, trauma or repetitive actions can result in breaking down this barrier and causing leakage into the nerve and accumulation of fluid. This further leads to pressure on the nerve and swelling.

An injury such as blunt trauma or a deep cut can result in isolated nerve dysfunction. Trauma usually causes nerve entrapment, with the most common being the tarsal tunnel syndrome.

Excessive pressure in the tibial nerve in the ankle causes this condition. The tarsal tunnel is the area of the foot where the nerve enters the back of the foot. Compression of this normally narrow tunnel results in symptoms such as weakness, numbness and muscle damage.

Nerve pain due to entrapment can lead to burning, tingling and prickling sensations. The symptoms of tarsal tunnel syndrome can start with intermittent tingling and numbing. However, the symptoms become more persistent with increasing pressure on the nerves.

Damage to the sciatic nerve, which runs from the lower back through the buttock and down the lower limb, can also result in nerve pain in foot.

The damage could be due to injury, disease or normal wear and tear. When the small discs cushioning the bones of the spine bulge abnormally or break open, it leads to herniated or slipped disc.

Usually, the symptoms affect only one leg with a pins and needles sensation. The first symptom is a sharp or burning pain starting at the back and moving towards the foot. Rest and medication along with physiotherapy can help relieve these symptoms in a few weeks.

Injuries to part of the spine could also lead to spinal stenosis. This condition is caused by the narrowing of the spinal canal. It is common for people suffering from arthritis. A specific symptom is painful leg weakness resulting in numbness in the foot.

Nerve pain in foot due to trauma can be avoided by being careful when doing repetitive activities. When exercising, make sure to take breaks between repetitions to avoid strain on the feet. The symptoms can be relieved by taking nerve-pain or anti-inflammatory medication.

Ideally, decreasing the pressure on the posterior tibial nerve is the best treatment for tarsal tunnel syndrome. However, walking or standing involve putting pressure on the feet. Shoe orthotics can help alleviate the symptoms for some patients. [7]

Infections

Post-herpetic neuralgia is a condition where a person starts feeling pain after infection with the shingles virus. This condition follows the viral infection and is common among those aged over 60.

The varicella-zoster virus causes this infection, with the virus also associated with chicken pox. In most cases, exposure to chickenpox makes the virus dormant in the body.

However, in some cases, a weak immune system might make the virus reappear. Shingles is characterized by a rash on one side of the body and can result in tingling or extreme pain. Anti-viral drugs can help prevent postherpetic neuralgia if taken at the onset of shingles.

Prompt treatment is recommended for people aged 50 diagnosed with shingles to prevent pain at a later stage. Estimates suggest one in five people with shingles suffering post-herpetic neuralgia. [8]

Lyme disease, caused by the Borrelia burgdorferi bacteria, is transmitted through an infected black-legged or deer tick. A rash on the bite site is the first symptom of the condition.

Symptoms include numbness, shooting pains or tingling in the hands or feet. Lyme disease needs to be treated the onset as the condition can result in peripheral neuropathy and weakness in the limbs if left untreated. Some of the symptoms of the disease affect the nervous system resulting in radicular (sciatica-like nerve) pain. Antibiotics can be used to help treat this condition. [9]

Alcoholism

Excessive and prolonged alcohol consumption is linked with alcoholic neuropathy. The level of nutrients such as niacin, thiamine, folate, vitamins B6 and B12, and vitamin E could be altered with prolonged alcohol consumption.

As these nutrients are necessary for proper nerve function, an alteration in these levels can result in alcohol-induced nerve damage. In most cases, alcohol abstinence can reverse the damage. However, in rare cases, nerve damage starts getting worse with continuing consumption and can also lead to permanent damage.

In such condition, the foot feels trickling, numbness sensations and cramps. The symptoms start appearing gradually over the course of months. The major symptoms include painful sensations with a burning feeling sometimes.

Alcohol-induced neuropathy is said to be related to nutritional deficiencies, especially thiamine. Chronic alcoholism is seen to be a risk factor for thiamine deficiency, with thiamine absorption in the intestine being reduced by ethanol.

Acetaldehyde and Oxidative-nitrosative stress are termed as the direct toxic effects of chronic alcoholism. The accumulation of acetaldehyde could be related to the pathogenesis of alcoholic neuropathy. [8]

Prevention and Treatment

The symptoms associated with nerve pain in feet can be relieved by pain-killers, self-care, and holistic therapies.

Medications

Over-the-counter and prescribed pain-relief medications are useful in relieving the pain associated with neuropathy.

It is essential that the recommended dose is followed. A dosage of an over-the-counter painkiller is advised initially before moving onto opioids.

  • Pain relievers – Mild symptoms can be relieved by the intake of over-the-counter pain medications, such as nonsteroidal anti-inflammatory drugs. It is noticed that the pain gets worse at night, but the patient is advised to not wait until night time to take the medicine.
  • Prescribed medications – Certain prescribed pain medications have been found to create dependency among users. Especially medications containing opioids are to be used if the pain is severe and not relieved by the painkillers.
  • Anti-seizure medications – Nerve pain in feet can also be treated by using medicines used for epilepsy treatment. However, drowsiness and dizziness are the side effects of such drugs.
  • Antidepressants – Some tricyclic antidepressants interfere with the chemical processes in your brain and spinal cord thereby reducing pain. Medications such as nortriptyline, amitriptyline, and doxepin can be used as treatment. Some of these medications can be used for treating post-herpetic neuralgia.
  • Diabetes-induced neuropathy can be treated with the extended-release antidepressants and serotonin and norepinephrine reuptake inhibitor duloxetine. However, the side effects include decreased appetite, nausea, and dry mouth.

Topical Treatments

Lidocaine patches and Capsaicin cream are known to offer modest pain relief. Capsaicin is a substance found in hot peppers. Application of the cream can lead to skin burning and irritation at the point of application but these sensations reduce gradually.

 Self-care

Maintaining normal glucose levels is the best treatment for diabetes-induced neuropathy. If you have diabetes, it is also necessary to check your feet for any injuries or cuts.

Endorphins are known as natural painkillers. You can relieve nerve pain by increasing blood flow to the nerves in the legs and feet. This can be achieved by regular exercise such as walking. A warm water soak for the foot can also temporarily increase blood flow to the legs.

Good sleep habits are necessary to relieve nerve pain, as the pain usually gets worse at night. Reduce caffeine intake in the afternoon and ensure a consistent bedtime is followed.

Maintaining proper nutrition is extremely important as nutritional deficiency can hamper pain treatments. [9]

Natural Treatments

Natural approaches such as yoga, meditation and acupuncture are known as pain and stress relievers. Acupuncture helps circulate and build vital energy. Meditation can reduce inflammation by calming the body. Yoga with easy stretching can relieve the burning sensations associated with nerve pain in foot.

Surgery

If a tumour is a cause for pressure on nerves, surgery is the course of action for removing the pressure and reducing neuropathy.

Additionally, therapies such as transcutaneous electrical nerve stimulation are also useful.

A painful sensation in the feet should not be ignored. It is important to be aware of the causes of nerve pain in feet to prevent it and treat it at the earliest. It is difficult to reverse the damage of prolonged nerve pain and nerve damage.

Strenuous activities such as rigorous exercise or sudden trauma to the feet can result in neuropathy. Treatment should be started at the onset of symptoms rather than waiting for it to become unbearable. Special therapeutic shoes can also be used to curb nerve pain in feet.

Habits such as chronic alcohol intake and smoking have also been known to be major factors for nerve pain. Lifestyle changes could go a long way in preventing complications.

Neuropathy in feet is an uncomfortable feeling that can affect our daily life. The ‘always-on-the-go’ lifestyle makes us keep going irrespective of the warning signs provided by the body. As our feet take the pressure of our body while standing and walking, it is necessary to ensure that we follow proper care and nutrition. Especially if the pain is a result of an underlying condition such as diabetes.

You can reverse nerve pain in feet if it is identified at the onset. It is important to not ignore any strange sensation in the foot, as mild symptoms can get better with self-care.

References

1. https://www.niddk.nih.gov/health-information/diabetes/overview/preventing-problems/nerve-damage-diabetic-neuropathies
2. https://www.onhealth.com/content/1/pain_causes_management
3. http://onlinelibrary.wiley.com/doi/10.1111/bcpt.12261/pdf
4. https://medlineplus.gov/ency/article/000700.htm
5. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1598252/pdf/brmedj00063-0029.pdf
6. http://onlinelibrary.wiley.com/doi/10.1111/bcpt.12261/pdf
7. http://nerve.wustl.edu/nd_tarsal.php?np=nerve_disorders
8. https://www.nhs.uk/conditions/post-herpetic-neuralgia/
9. https://www.aan.com/Guidelines/Home/GetGuidelineContent/243
10. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3370340/
11. https://www.webmd.com/pain-management/nerve-pain-self-care

Dr. Sachin
 

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