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The Nitty Gritty of Neuropathic Pain

By: Melissa Ngo, MDThe Nitty Gritty of Neuropathic Pain

 “Manhid, ngalay, kirot, parang may tumutusok” – these are just some of the complaints of patients with neuropathic pain. Neuropathic pain, also called neuralgia or neuritis, arises from the damage of the somatosensory nervous system by a lesion or a disease.  This somatosensory system involves the nerves located in the skin, joints, muscles, and fascia (fibrous tissue enclosing a muscle or organ). These nerves enable people to perceive sensations such as touch, pressure, temperature, pain, movement, vibration, and position. When these nerves are destroyed, they either transmit abnormal, increased or decreased sensations to the brain.

Neuropathy is not a disease in itself but rather a symptom of a myriad of disorders or lesions which destroy nerves. The diagnosis and treatment of neuropathy is a complicated journey. Initially, most patients with neuropathy, especially those with numbness, have a “wala ‘yan” or “tiisin na lang” attitude. Those patients bothered by the pain often just self-prescribe with paracetamol or other analgesics but find themselves unrelieved. Numerous patients live with the pain for prolonged periods and consult doctors too late when there is already considerable and irreversible nerve damage.

What are the symptoms of neuropathic pain?

Abnormal or increased sensations like:

  • Dysesthesia – abnormal sensations such as crawling, itching, tingling or burning
  • Paresthesia – spontaneous painful or unpleasant feelings such as pins and needles or electric shock-like pain
  • Allodynia – unbearable pain after non-harmful stimuli such as a wisp of cotton causing sharp pain or cramps
  • Hyperalgesia – heightened or severe pain after a stimulus that would normally cause only discomfort or minimal pain such as a pinprick causing severe pain

Decreased sensations such as:

  • Numbness – loss of sensation
  • Hypoalgesia – reduced quality or severity of sensation  such as reduced ability to feel pain or temperature changes

Other symptoms such as:

  • Muscle weakness
  • Loss of reflexes
  • Loss of balance and coordination

Who is affected by neuropathic pain? What are the causes?

Chronic neuropathic pain most commonly affects the lower back, limbs, hands, feet, and neck. It is more frequently encountered in patients above 50 years old (8.9% versus 5.6% in younger individuals) and among women more than men (8% versus 5.7%).

Statistics show that up to 25% of patients with diabetes have some type of neuropathic pain. However, neuropathy does not only occur among diabetics but in other individuals with:

  • Nutritional deficiencies such as those lacking vitamin B12 due to alcoholism or being on a purely vegan diet
  • Low vitamin B6 production due to isoniazid therapy for tuberculosis
  • Infections such as shingles (post-herpetic neuralgia), syphilis, HIV infection, and AIDS
  • Spinal cord or nerve compression problems such as those with herniated discs, spinal arthritis, and carpal tunnel syndrome
  • Nerve damage from toxins due to uremia or chemotherapy for cancer
  • Endocrine problems such as thyroid disorders
  • Immunological disorders such as multiple myeloma and multiple sclerosis
  • Brain injury such as stroke
  • Nerve damage from amputation or ‘phantom limb’ syndrome
  • Nerve damage due to aging or injury such as trigeminal neuralgia and lumbar plexus neuralgia

How is neuropathic pain diagnosed?

During a consultation, the physician will conduct a thorough review of the patient’s medical history and other body systems to identify the possible location of the lesion and cause of the nerve damage. It is important that the patients describe the symptoms, the timing of the attacks, what aggravates and relieves the pain, and share other diseases they may have, medications they are taking, past infections, surgeries or injuries, their habits, and their lifestyle. Patients may also be asked to fill up neuropathic pain screening questionnaires such as the McGill Visual Analog Scale, the validated Filipino translation of the ID pain, and the SIGN-PQ.

Physical and neurological examination will be performed. If needed, blood and serological laboratory tests will be requested to rule out nutritional deficiencies, toxins, and endocrine problems. Confirmatory tests for nerve damage may include electromyography-nerve conduction velocity (EMG-NCV) test for large fiber abnormalities, skin biopsy for decreased intraepidermal nerve fiber density, and magnetic resonance imaging (MRI) to identify strokes, spinal cord damages, and nerve compressions.

How is neuropathic pain treated?

The management of neuropathic pain involves correction of the etiology or cause of the problem. This may include nutritional supplements for those with deficiencies or on isoniazid therapy, glucose control for diabetics, hormonal therapy for thyroid disorders, anti-viral medications for those with infections, steroids for immune disorders or surgery for compression problems or spinal deformities.

Furthermore, there are 4 main classes of medications, which either enhance or block nerve transmissions to reduce the pain associated with neuritis. These are the tricyclic antidepressants (TCA), serotonin and norepinephrine reuptake inhibitors (SNRI), anti-epileptics, and opioids. The aim of drug therapy is to always use the lowest possible dose that eases the pain to avoid side effects. Among the drugs, patients taking anticonvulsants, such as pregabalin and gabapentin, report considerable relief. These drugs are also ideal for patients with anxiety disorders due to their tranquilizing properties.

When taking these medications, it is important for patients to understand that the drug may take 2-3 weeks before a beneficial effect. They should not abruptly stop the medication unless advised by their doctor. If after 4-6 weeks there is no considerable relief (<30%), or any time they experience an untoward reaction, patients should follow up with their doctor for a change in drug dose or medication.

All of these classes of drugs should only be taken upon the advice of a physician due to significant side effects, especially with improper use. These drugs can cause drowsiness or dizziness and patients are cautioned against driving or operating heavy machinery. Likewise, elderly patients should be assisted to avoid the risks of falls or injuries due to impaired mental functioning.

Other supportive medications used to relieve neuropathic pain include lidocaine 5% patches or capsaicin cream. Patients should not apply more than 3 lidocaine patches a day or leave the patch for more than 12 hours. Capsaicin cream can be applied 3-4 times a day but it may only give slight relief from pain. Patients are advised not to apply the cream to wounds or inflamed skin and to wash hands immediately after application.

Regarding B vitamins, they are mainly used to prevent neuropathy. However, there is limited evidence to support that vitamin B complex can reduce neuropathic pain or reverse nerve damage. Specialists advise not more than 40 mg of supplemental vitamin B1 (thiamine) per day in patients with thiamine deficiency and not more than 10 to 20 mg of vitamin B6 (pyridoxine) per day for patients with neuritis due to isoniazid. Patients are generally advised not to exceed the required daily intake for adults: thiamine 1.0 to 1.5 mg, riboflavin 1.2 to 1.7 mg, pyridoxine 1.4 to 2.0 mg, niacin 13 to 19 niacin equivalents, cobalamin 3 to 5 mg, and folic acid 50 mg.

Why and how should doctors treat the associated problems beyond the pain?

Patients with neuropathic pain experience decreased quality of life. Physicians treating these patients should not only address the symptoms of pain but other associated complaints such as: sleep disorders, poor attention and concentration, poor appetite, lack of energy, depression, and anxiety. To help patients, doctors may advise:

  • Psychological interventions such as cognitive-behavioral therapy, relaxation techniques, pain acceptance therapy, and stress management
  • Rehabilitation medicine, physical therapy, and low-impact exercise regimens
  • Transcutaneous electrical nerve stimulation (TENS), therapeutic ultrasound, and acupuncture
  • Social interactions with family and friends and participating in patient support groups
  • Staying active for general physical and emotional well-being
  • Modifying lifestyle such as a shift to a healthy diet, avoidance of alcohol consumption, and smoking cessation
  • Protective and assistive devices for ambulation such as braces, walkers, and canes
  • Appropriate footwear
  • Ergonomic furniture and tools

Now that we have run through what you need to know about neuropathic pain, it is crucial that you take action once the sensation hits. Get help if it is unmanageable to handle by yourself and keep your medications handy. After all, you have to have some nerve to beat neuropathic pain.

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