Postherpetic Neuralgia

 

Postherpetic neuralgia is a chronic pain syndrome that may occur after shingles, which is caused by the Varicella Zoster Virus. The Varicella Zoster Virus is the cause of the childhood disease, chicken pox. Shingles is caused by the re-activation of the virus and usually begins as a painful rash upon the body or face. The pain usually resolves with the healing of the rash but if it continues for greater than three month after the resolution of the rash then it is termed postherpetic neuralgia.
 

 

If the eye is affected by ophthalmic herpes, your doctor is likely to ask an eye specialist to see you as a matter of urgency. The treatment is likely to involve anti-viral eye drops, and oral medications.
 

 

Cause of Shingles Shingles is the re-activation of the Varicella Zoster Virus. After the resolution of chicken pox, the virus remains dormant in the nerves. High stress levels, excessive consumption of alcohol, or a compromised immune system may contribute to a shingles outbreak. The virus causes an inflammation of the nerve and to the surrounding skin. The pain is likely produced both by the inflammation associated with the movement of viral particles from sensory nerves to skin and subcutaneous tissues as well as the damage to nerve structures. The resulting damage to the nervous system may make the patient more sensitive to pain afterwards. The patient may have pain even to sensations which do not normally cause pain termed allodynia.

 

Presentation of Shingles

 

Shingles is most commonly characterized by the single-sided rash upon the body in a stripe. The rash follows the area of the skin innervated by the affected nerve. The rash will be made up of grape-like clusters of small, clear, fluid-filled blisters on reddened skin. Within three days after the rash appears, the fluid-filled blisters will turn yellow, dry up, and crust over. The upper body and face are the most commonly affected areas. Pain is the most common symptom of shingles and may precede the rash by days or weeks. Occasionally pain is the only manifestation. The pain associated with shingles is a neuropathic pain which may feel like burning, sharp, stabbing, tingling, or numbness. The affected areas may have allodynia or even numbness. Other areas of the patient’s life may be impaired including sleep, decreased appetite, and diminished libido.

 

Treatment

 

The first type of medication for treatment would be antiviral agents such as acyclovir (Zovirex), valacyclovir (Valtrex), and famciclovir (Famvir). They can help reduce the shingles pain and may aid in healing of the rash. These agents decrease the production of the Varicella Zoster Virus
 

 

The tricyclic antidepressant medications can help decrease the postherpetic neuralgia pain by inhibiting the re-uptake of neurotransmitters in the central nervous system. The tricyclic antidepressants are often thought of as the mainstay of therapy for postherpetic neuralgia but are limited by their side effects of drowsiness, dry mouth, and weight gain. Some of the available tricyclic antidepressants are amitriptyline (Elavil, Endep), clomipramine (Anafranil), desipramine (Norpramin), doxepin (Sinequan, Adapin), imipramine (Tofranil), nortriptyline (Pamelor), protriptyline (Vivactil), and trimipramine (Surmontil). Some of the newer antidepressants such as selective norepinephrine reuptake inhibitors may be beneficial in the treatment of neuropathic pain.
 

 

Opioids are effective in the treatment of postherpetic neuralgia. They should be used in combination with the other medications available. They do have side effects of constipation, nausea, and itching.
 

Anti-convulsant medications have had some success treating the neuropathic pain caused by postherpetic neuralgia. Gabapentin (Neurontin) was the first oral agent approved for the treatment of postherpetic neuralgia. A new medication, pregabalin (Lyrica), has been approved for the treatment of postherpetic neuralgia also. Older medications that have been used for treatment include carbamazepine (Tegretol), valproic acid (Depakene, Depakote), and phenytoin (Dilantin).
 

 

Steroids have been used during shingles in an attempt to reduce the incidence or duration of postherpetic neuralgia. Prednisone should be considered for any patient without a contraindication to corticosteroid therapy. Pain specialists can also administer steroids to the spinal cord via epidural or spinal routes.
 

 

Topical medications are available to be placed upon the affected areas of the skin. The lidocaine patch (Lidoderm) can help numb the skin and provides a protective barrier. Capsaicin cream (Zostrix, Capzasin-P) is made from the seeds of the hot chili pepper and can help deplete the chemicals sending the pain impulses called Substance P. It may relieve the skin of hypersensitivity but may also cause a burning sensation.