New treatments for Postherpetic Neuralgia (Chronic pain after shingles)

     The photo below looks like a fried egg, doesn't it? Well, it is actually an electron micrograph of the Varicella zoster virus. This virus is the cause of chickenpox and a painful rash called shingles. Another name for this virus is Herpes zoster. It is a cousin to the Herpes simplex virus that causes cold sores. Both Herpes viruses have the tendency to hook into the DNA of nerve tissue and lie dormant for years or even for a lifetime. Then through some reduction in immunity or other stimulation that we don't understand, the virus which has been in the nerve cell since that person had chickenpox as a child, can become active and reproduce itself . When Herpes zoster does this, the virus reproduces in the nerve cell, and is transported inside the nerve cell to the skin where it then reproduces more and causes the painful rash known as shingles.

     Many Tuesday mornings, I have been atttending Grand Rounds at the new Columbia St. Mary's Hospital. It keeps me up to date on medical topics and I sometimes see some of my former colleagues there. This week's topic was a discussion of new treatments for postherpetic neuralgia. This syndrome involves a chronic pain arrising from nerve endings that were damaged and irritated by the Herpes zoster virus when it comes out of dormancy and reproduces itself in the form of shingles. This recurrent infection occurs particularly commonly in people who are immunosuppressed and who are elderly.

   

  The usual shingles patient will first develop some burning pain in a dermatome area for a specific nerve of the body. (A dermatome is an area of the skin supplied by a defined known anatomical nerve; thee dermatomes are the same for all people) The rash might be on the trunk on one side, or on one limb, or even on the head or face, only on one side of the body. Then within a day or two, the person develops a painful blistering rash on a red base in that area. This rash progresses over several days and the blisters coalesce. Later they crust over, scab and heal sometimes with scars. The pain may persist after the rash has healed without becoming chronic pain (greater than 6 months duration). There are antiviral medications that can be started within 72 hours of the onset of the rash. This medication can shorten the duration of this whole rash, scabbing, pain, and clearing course of the illness. This medication can also reduce the incidence of the postherpectic neuralgia syndrome. So if you develop a rash that looks something like the picture above located on only one side of the body and following a dermatome distribution, you should see your doctor in order to get a prescription for the antiviral pills.

A nerve with all its connections.

     To give you an idea of the frequency of this illenss, about 1 million people suffer from shingles every year. Within that group, about 10% of those below 60 years old will suffer chronic pain after the healing of the skin rash. In the group that is over 60 years old, 40% will suffer this chronic nerve pain. This pain is defined by a duration of greater than 6 months but it can go on for years or even indefinitely. It can be shooting, lancinating, electric shock types of pain. Or it can be burning and steady. It can be a hypersensitivity to light touch, to movement, or pain from stimulation that should not be painful. It can interfere with work, sleep, lifestyle, and can cause depression.

     Various treatments that have been used in the past include anti depressant pills, anti convulsant medications, lidocaine gel or cream applications, and opiates as pain relievers. The latter are not as affective for this type of chronic pain as for postsurgical pain, for example. The purpose of the anti depressants and anti convulsant medications is to try to interfere with and block the constant pain messages that are being sent to the central nervous system. It is postulated that there is a change in the nerves themselves so that they react differently to the recurring pain messages. The nerve receptors become sensitized to these pain messages and then keep firing even in the absence of tissue damage. In severe and protracted cases of pain, surgery is sometimes done to cut the nerves that are sending the pain. This is usually a last resort because sometimes permanent nerve damage results and depending on which nerves need to be cut, the surgery can cause gait disturbances or reduction of use of a limb, for example. .

      Another treatment that has some benefit is application of capsaicin cream. Capsaicin is the ingredient in chilly peppers that makes your mouth burn and your eyes burn if you rub the chilly  fluid in them. The theory here is that the burning created when this cream is applied to the skin overwhelms those pain nerve endings and wears them out, interrupting the pain messages that can be sent from the area. But this cream has been very hard to use. It requires regular application daily with its associated buring sensations for several months and then it may not be affective. This cream was only a 0.25% concentration. Now a new medication has been developed which is 8% capsaicin. It is called Qutenza. It is applied for 1 hour under conscious sedation for that time period to stop the painful burning that occurs with the application. This treatment has been much more effective than the weaker cream and in 50% of the time the pain is completely eliminated. In the other 50% there are varying degrees of relief. The treatment can be repeated everey 3 months. This new form of treatment is very exciting. It would seem to offer a new form of use for an old class of medication with great hope to improve the outlook for this devestating chronic pain syndrome.

     It should be noted that there is now a vaccine for herpes zoster. It is given to adults in 4 times the dose that is given to children to prevent chickenpox. People over 60 years should get this vaccine to reduce the chance that they will get shingles. People over 60 are at higher risk to get shingles and if they get shingles they are at higher risk to have a resultant postherpetic neuralgia. So also think about getting the Herpes zoster vaccine. And if you know anyone who has chronic pain resulting from shingles, let them know about this new treatment. Qutenza would be administered by an anesthesiologist who specializes in the treatment of chronic pain.