Postherpetic Neuralgia

THE CLINICAL SYNDROME

One of the most difficult pain syndromes to treat, postherpetic neuralgia will occur in 10% of patients after a bout of acute herpes zoster. The reason that this painful condition occurs in some patients but not others is unknown, but it occurs more frequently in older patients and appears to occur more frequently after acute herpes zoster of the trigeminal nerve as opposed to acute herpes zoster involving the thoracic dermatomes. Conditions that cause vulnerable nerve syndrome, such as diabetes, may also predispose the patient to develop postherpetic neuralgia. It is the consensus among pain specialists that aggressive treatment of acute herpes zoster will help the patient avoid postherpetic neuralgia. The pain of postherpetic neuralgia is characterized as a constant, dysesthetic pain that may be exacerbated by movement or stimulation of the affected cutaneous regions. There may be sharp, shooting neuritic pain superimposed on the constant dysesthetic symptoms. Some patients suffering form postherpetic neuralgia will also note a burning component reminiscent of reflex sympathetic dystrophy.

SIGNS AND SYMPTOMS

As the lesions of acute herpes zoster heal, the crusts fall away, leaving pink scars in the distribution of the rash that gradually become hypopigmented and atrophic. These affected cutaneous areas are often allodynic, although hypesthesia and rarely anesthesia of the affected areas may occur. In most patients, these sensory abnormalities and pain generally resolve as the skin lesions heal. In some, however, pain may persist beyond lesion healing.

Allodyna and dysesthesia are characteristic of the pain of postherpetic neuralgia.

TREATMENT

The primary goal of all clinicians caring for patients with acute herpes zoster is the rapid and aggressive treatment of symptoms to help decrease the incidence of postherpetic neuralgia. It is the consensus of most pain specialists that the earlier in the natural course of the disease that treatment is initiated, the less likely the patient will develop postherpetic neuralgia. Furthermore, because the older patient is at highest risk for the development of postherpetic neuralgia, early and aggressive treatment of this group of patients is mandatory. Should despite everyone’s best efforts postherpetic neuralgia occurs, the following treatments are appropriate.

Adjuvant Analgesics

The anticonvulsant gabapentin represents a first line treatment in the palliation of pain of postherpetic neuralgia. Treatment with gabapentin should begin early in the course of the disease, and this drug may be used concurrently with neural blockade, opioid analgesics, and other adjuvant analgesics, including the antidepressant compounds if care is taken to avoid central nervous system side effects. Carbamazepine should be considered in patients suffering from severe neuritic pain in whom nerve blocks and gabapentin have failed to bring relief.

Antidepressant Compounds

Antidepressants may also be useful adjuncts in the initial treatment of the patient suffering from postherpetic neuralgia. On an acute basis, these drugs will help alleviate the significant sleep disturbance that is commonly seen in this setting. In addition, the antidepressants may be valuable in helping ameliorate the neuritic component of the pain, which is treated less effectively with narcotic analgesics. After several weeks of treatment, the antidepressants may exert a mood-elevating effect that may be desirable in some patients.

Nerve Blocks

Sympathetic neural blockade with local anesthetic and steroid via either epidural nerve block or blockade of the sympathetic nerves subserving the painful area appears to be a reasonable next step if the aforementioned pharmacologic modalities fail to control the pain of postherpetic neuralgia. The exact mechanism of pain relief from neural blockade when treating postherpetic neuralgia is unknown, but it may be related to modulation of pain transmission at the spinal cord level. In general, neurodestructive procedures have a very low success rate and should be used only after all other treatments have been optimized, if at all.

Opioid Analgesics

Opioid analgesics have a limited role in the management of postherpetic neuralgia and in the experience of this author frequently do more harm than good.

Adjunctive Treatments

The application of ice packs to the area affected with postherpetic neuralgia may provide relief in some patients. The application of heat will increase pain in most patients, presumably because of increased conduction of small fibers, but it is beneficial in an occasional patient and may be worth trying if the application of cold is ineffective. Transcutaneous electrical nerve stimulation and vibration may also be effective in a limited number of patients. The topical application of capsaicin may be beneficial in some patients suffering from postherpetic neuralgia. However, the burning associated with this drug when applied to the painful area will often limit the usefulness of this intervention.

Low intensity laser therapy as well as a coordinated wellness program is also effective in treating this disorder.

Low Intensity Laser Therapy (LILT)

The low intensity Laser (LILT) sends photons (light) into the injured tissues and can penetrate two to three inches to treat affected areas. It uses a natural enhancement of the cellular machinery that can and has been dynamically measured in published studies to promote healing without burning affected tissue. Once the photons find the injured tissues, they stimulate and energize the cells to repair and strengthen at a remarkable rate. The treatment does not hurt, takes about 30 minutes and is very cost advantageous.

Wellness Program

A wellness program whichindividualizes treatment for age, performance and function has been shown in pilot studies to improve the overall health and well being of the individuals evaluated. A well conceived dietary and supplementary regimen based on scientific age–related decline in certain necessary compounds can improve quality of life, correct the ravages of hormone imbalance, balance critical neurotransmitter function without resorting to powerful drugs for depression that often have unfavorable side-effect profiles and restore vitality and youth in daily exercise routines. Furthermore, when wellness products are utilized with success, individuals often seek less costly interventions including unnecessary surgeries and narcotic options to treat pain. For more information go to www.drpwellness.com.