What is a Post herpetic neuralgia?
Chicken Pox is an infection of the varicella-zoster virus. It remains dormant in the body after a single episode of chicken pox. Shingles or herpes zoster is caused by the reactivation of this same varicella-zoster virus. This leads to a sore, blistering rash and other discomforts. The rash often forms a stripe on one side of the body, commonly on the back or abdomen region. The rash develops into blisters. The pain from the rash/blister may linger even after they heal. This persistent pain is known as postherpetic neuralgia (PHN).
How long does postherpetic neuralgia (PHN) can last?
About 50% of the patients get better within a year, but the rest have different outcomes. One study found that the chance of the pain going away by itself got lower as time passed since the shingles started.
What type of pain postherpetic neuralgia (PHN) patient experience?
The pain from PHN can feel like burning, shooting, throbbing or electric shocks. It can happen on its own or be triggered by something. It usually affects the chest wall (thoracic dermatomes) or the area around the eye (if ophthalmic branch of the trigeminal nerve is involved). The pain can get worse at night or when you are stressed. The area may also be very sensitive to touch. Some people may have muscle weakness too.
Is postherpetic neuralgia (PHN) very common?
It is quite common. An approximate of 10 to 18% of people who get shingles or herpes zoster will develop postherpetic neuralgia.
Risk factor of getting postherpetic neuralgia (PHN)
Some factors make you more likely to get postherpetic neuralgia (PHN) after having Herpes Zoster. These include:
Age: Older people are more prone to PHN than younger ones. Shingles can cause more intense and lasting pain in older people. PHN affects about 10 to 13% of people over 50 who had shingles. It is very rare in people under 40.
Immunity: Your immune system gets weaker as you age. This can let the varicella-zoster virus, which causes shingles (herpes zoster), become active again. Some health conditions and medicines can also weaken your immune system. These include cancer, chronic infections (like HIV/AIDS), organ transplants, chemotherapy, immunosuppressants, steroids and anti-rejection drugs.
Shingles severity: Initial severe rash from shingles can increase your risk of PHN later.
Skin sensations before shingles rash appears: If you felt pain, itching, or tingling in a skin area before the shingles rash appeared, you have a higher chance of PHN.
Delay in starting the treatment of herpes zoster: If you did not start treatment within three days of the rash starting, you are more likely to get PHN.
Prevention and Treatment of Post Herpetic Neuralgia
Prevention
To prevent PHN, you need to get vaccinated against herpes zoster and use antiviral drugs early if you are already infected. You also need to control your pain quickly by strong pain medicines when it starts. Sometimes, oral steroids can help.
Treatment
Treating long-lasting pain can be hard for even a Pain Specialist. You may need to take different kinds of medicines, both by mouth and on your skin (gels/patches/creams). Sadly, some of the skin medicines like 8% capsaicin patch are not sold in India yet.
Pain procedures:
Besides medicines, you can also try other treatments like nerve blocks, drug infusions, neuromodulation. These can block or change how your nerves feel pain. Sympathetic nerve blocks like stellate ganglion block or lumber sympathetic blocks are common. But they are not 100% effective or applicable in all the cases. If the effect weans off after a short time, you may need to do them again. Intercostal nerve CRYO analgesia or radiofrequency neurolysis are some of the options of treatment.
Prognosis of Post herpetic neuralgia
Pain from PHN usually gets better over time and disappears for most people. It often takes one to three months for the pain to go away. If it continues for more than the expected recovery time, PHN becomes difficult to treat. As per a large study, achieving a complete symptom-free state was achieved in less than half the patients with PHN.
Who should get a herpes Zoster Vaccine?
Zoster vaccine is recommended in healthy adults aged 50 and older. You can get the vaccine at any age. You should get it even if: 1. You had shingles before. 2. You don’t know if you had chickenpox.
If you are a herpes zoster patient at present, then you need to wait until the shingles rash is gone.
You can always contact Dr CHINMOY ROY, MD, FIPP (WIP-USA) at Rajarhat Pain Clinic, Newtown, Kolkata for treatment of Post Herpetic Neuralgia.
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