What Is Peripheral Neuralgia?
Peripheral neuralgia refers to pain occurring as a result of damage to the peripheral nervous system. The peripheral nervous system is the network of nerves outside of the brain and spinal cord that serve most of the body. Damage to this system, or peripheral neuropathy, may result in adverse effects to many other functions of the body, such as digestion, motor control, and sensory perception. Neuralgia, pain resulting from nervous system damage, may be magnified forms of normal stimuli that cause pain, or manifest in response to nothing at all due to peripheral nerve damage. It may also be chronic, or experienced constantly due to faulty nervous impulses.
Many cases of peripheral neuralgia are perceived as a consistent burning sensation. Peripheral neuralgia may result in significant reductions in the ability to function or even move normally. Chronic peripheral nerve damage contributes to a healthcare expenditure of approximately 600 billion dollars per year. It is estimated that up to 8% of the population suffer from peripheral neuralgia.
Causes Of Peripheral Neuralgia
Many conditions and factors are associated with an increased risk of peripheral neuralgia development. These include:
- Diabetes: Diabetes is a condition in which glucose cannot be metabolized properly, leading to an increasingly harmful concentration of this sugar in body tissues. This build-up may cause damage to peripheral nerves, resulting in symptoms ranging from numbness in the extremities to chronic pain, which often manifest at night. As diabetes also has an autoimmune component, inflammation may contribute to the pain of diabetic neuropathy.
- Herpes zoster virus: Pain associated with inflammation is also a hallmark of postherpetic neuralgia, which is peripheral nerve damage as a consequence of infection with herpes zoster (the virus associated with shingles). This may also present as chronic pain, resulting from permanent nerve damage caused by the virus.
- HIV: The HIV virus, associated with AIDS, is also associated with peripheral nerve damage. This is thought to be due to both direct viral damage, and as a side effect of certain drugs used to treat the condition.
- Cancer: Another factor associated with peripheral (and central) nervous system damage is cancer. Both malignant tumors, and the destructive chemotherapy compounds administered to kill them, may cause long-term nerve damage, which often manifests as chronic pain.
- Injury: Peripheral nerve damage may also occur as a result of direct mechanical damage resulting from injury.
Treatments For Peripheral Neuralgia
The first-line treatment following a diagnosis of peripheral neuralgia is often drug therapy. Certain antidepressants, including duloxetine, venlafaxine, and tricyclic antidepressants are associated with effective pain relief in cases of peripheral nerve damage. Anticonvulsants such as gabapentin are also occasionally recommended for this condition. A more novel pharmacological treatment for peripheral neuralgia are capsaicin patches. These are transdermal (i.e. patches permeated in the drug and applied to the skin so it may be absorbed into the body in this way) applications of a molecule found in chili peppers. It may seem counter-intuitive, but the administration of capsaicin, though possibly irritant, reduces the sensitivity of targeted nerves to pain over time. The drawback of capsaicin patch use is, as mentioned, that many patients find the concomitant skin irritation intolerable. This can be addressed with a mild dose of local anesthetic beforehand, however.
Peripheral nerve stimulation is associated with some success in treating diabetic peripheral neuropathy and neuralgia related to injury. This is a surgical intervention, but is minimally invasive. It involves electrical stimulation of the nerve(s) in question, also known as neuromodulation. The procedure involves locating nerves transmitting chronic pain signals and the implantation of small electrodes into the tissues surrounding them. Imaging techniques, such as fluoroscopy, are used to ensure accurate device placement to reduce the risks of damage to surrounding tissues. The implanted electrodes emit a mild electrical impulse (which can be controlled by the patient) in response to pain. The goal of this stimulation is to correct the abnormal signaling caused by damaged peripheral nerves, thus significantly reducing pain. The implant will be tested and monitored by the physician or pain specialist to ensure normal function and a lack of side effects or implant malfunction. Some reports indicate that peripheral nerve stimulation is a safe and effective alternative for patients who have found their pain is resistant to other treatments.
Peripheral nerve stimulation is usually performed after a trial stage in which an eligible patient (eligibility is determined by diagnosis of treatment-resistant peripheral neuralgia and evaluation by a pain specialist) receives a temporary implant and tests its neuromodulatory effects for about a week. If this proves to be safe and effective, the surgery in which permanent electrodes are implanted goes ahead. If not, the temporary device is removed and the patient discusses other treatment options with their specialist. The actual procedure may be done under local anesthetic. Peripheral nerve stimulation is an increasingly safe and standard procedure in chronic pain treatment, but is associated with some risks. These include infection, bleeding, and tissue damage at the site of device implantation. In addition, there are some cases of faulty implant signaling, which may paradoxically magnify pain or cause additional nerve damage that may lead to sensory or motor control damage. In these cases, the implants must be removed. Peripheral nerve stimulation is associated with long-term, significant reductions in pain and medication use for many patients.
Peripheral neuralgia is a condition in which damage to nerves in the peripheral nervous system results in chronic pain. It may be associated with some viruses that may mediate damage to the tissues they infect, including nerves. Alternatively, peripheral neuralgia may result from injury, cancer, or from the effects of the disease diabetes. There is no direct cure for this condition; therefore, the goal of treatment is to reduce pain as effectively as possible.
Peripheral neuralgia can be managed using pharmacological means. If this line of treatment fails, a patient may consider peripheral nerve stimulation. This is a form of neuromodulation in which a device implanted near a dysfunctional nerve emits electrical impulses to correct chronic pain signals.