Is there a shot or patches that I can take for postherpetic neuralgia?
Postherpetic neuralgia refers to the pain, which can be very severe, that persists after an attack of herpes zoster or shingles. Herpes zoster is caused by a recurrence of varicella-zoster virus. As the name implies, varicella-zoster virus also causes varicella or chickenpox, and it is only in someone who has had chickenpox, perhaps dozens of years before, that herpes zoster appears.
Varicella-zoster virus (VZV) is a member of the herpes family of viruses, which also includes herpes I, the cause of herpes in the mouth; herpes II, the cause of genital herpes; Epstein-Barr virus (EBV), the cause of infectious mononucleosis; cytomegalovirus (CMV), also a cause of infectious mono; and others. These viruses are all very common. Before the development of a vaccine, 90 percent of the population would have had chickenpox by age 15. Herpes I is present in the mouths of about 80 percent of the population, herpes II in the genitals of about 40 percent, EBV persists in 90 percent, and CMV in about 40 percent.
Perhaps the most interesting attribute of these viruses is that once a person is infected, the virus remains hidden in the person’s body for the rest of their life. In people with normal immune systems, this usually has few consequences. Most of us carry EBV to our graves without ever being aware of it. But some of the herpes viruses can break out of the grip of our immune system and cause recurrences. Recurrent herpes on the lips or genitals is one example, and herpes zoster is another, often painful one. Even those that rarely cause problems, like EBV, recur without producing symptoms from time to time and make the person infectious to others who have not had the infection. EBV is shed in the saliva and 90 percent of us have it because our parents kissed and hugged us while they were shedding virus when we were kids.
When a child is infected by VZV, the virus travels through the blood stream, producing the typical vesicles over the skin surface. It can also, rarely, infect the brain causing encephalitis, or in the lungs, causing pneumonia. In most cases the immune system kills off the virus, except in certain nerve cells that make up the dorsal root ganglia, the small clumps of nerve tissue along our spinal cords that contain the cells receiving nerve impulses from our skin. Each dorsal root ganglion sends out nerve fibers to a swath of skin surface shaped like a strip around the body, or down the legs or arms or face. These strips are called dermatomes, and account for the strip like appearance of the vesicles of herpes zoster. Probably all the dorsal root ganglia contain latent virus, so why a particular dorsal root ganglion happens to have its virus reactivated and not another is still unknown.
An attack of herpes zoster usually begins with pain in a strip around the body, down the leg, etc. Most attacks involve the chest or abdomen, and are most common after age 50. Within 2 to 3 days, the typical vesicles, which look just like the vesicles of the chickenpox which the person surely had years before, erupt. During the time that the vesicles are present the person is infectious to others, but only to someone who has not had chickenpox, and that person will catch chickenpox, not herpes zoster. The skin normally heals within four weeks, but the pain may persist much longer, even indefinitely. This is the postherpetic neuralgia and its treatment can be very difficult.
Treatment of the outbreak early with acyclovir (Zovirax) or one of its relatives reduces the likelihood of someone developing postherpetic neuralgia. Some doctors believe that giving a short course of prednisone, a cortisone type drug, with the acyclovir further reduces the risk of the neuralgia. But, unfortunately these treatments are only useful early, and will not help the neuralgia once it is established, as appears to be your case.
Standard pain medicines like ibuprofen or naproxen rarely relieve the pain, and doctors are often reluctant to prescribe stronger medications for fear of addiction, although there is evidence that this is not a problem if codeine or one of its derivatives is prescribed carefully.
Several drugs that are antidepressants like amitriptyline (Elavil) or anticonvulsants like divalproex (Depakote) or gabapentin (Neurontin) have been found to reduce nerve type pain, and should be tried in someone with this neuralgia. These drugs do have side effects, but have no addiction potential, and can be taken along with codeine or other pain medications.
Transcutaneous electrical neural stimulation (TENS) which consists of electrodes applied to the skin which are stimulated by a battery pack may reduce the pain, although the mechanism is unclear. It may be that the constant electrical stimulation overwhelms the nerves conducting pain impulses and blocks them from conducting.
In severe cases, postherpetic neuralgia should be treated by a specialist in pain management who will be familiar with all the different treatments and the ways to combine them for most effective control.