Post Herpetic Neuralgia: Essential Facts

Post-herpetic neuralgia (PHN) is a side-effect of shingles

PHN is the most common complication of shingles. It follows on from shingles after the rash has cleared up.

The main symptom of PHN is persistent pain

PHN causes continuing pain, after the rash from shingles has healed. The pain is caused by scarring of nervous system tissue in the spinal cord. It may be burning, stabbing, or throbbing, and it may affect more areas than the original shingles pain.

The pain can occur in response to minor stimuli. Normally painless things (such as the light touch of clothing) can cause pain, and things that would normally cause slight discomfort become extremely painful.

There are no tests for PHN

There are no blood tests, X-rays or other tests to diagnose or predict PHN.

Health professionals diagnose shingles according to the symptoms described by the patient. These include:

• A recent outbreak of shingles
• Pain persisting for at least a month after the rash has healed

The course of PHN can vary

PHN usually recovers completely—even without treatment—but the time for recovery can vary between patients. About 20 per cent of people with shingles develop post-herpetic neuralgia. Three months after shingles, seven percent are affected. One year later, only four per cent still have pain.

Older people are more likely to develop PHN

Post herpetic neuralgia is more frequent in people who are over 50. This is thought to happen as the immune system gradually becomes less efficient. As age increases, the likelihood of developing PHN after an attack of shingles increases further, as does the duration of the pain. People over 70 are several times more likely to have pain at six months than those aged 50-70.

PHN is more likely after severe attacks of shingles

Studies have shown that the more painful the outbreak of shingles, the more likely it is that the patient will develop PHN. Post herpetic neuralgia is also more likely if the pain occurred before the rash appeared.

Problems with the immune system, such as HIV or drugs that suppress the immune system, can increase the likelihood of PHN.

You can’t “catch” post-herpetic neuralgia

PHN isn’t an infectious disease. It results from damage and scarring caused by shingles.

Shingles is caused by a virus (varicella-zoster virus, or VZV), but in most cases the patient was exposed to the virus many years earlier. When a person first contracts VZV, they develop chickenpox. After recovery, the virus lies dormant without causing problems for many years. In some cases, it “wakes up” to cause shingles. Older people and those with damaged immune systems are more likely to experience shingles, although it does occur in younger, healthy people.

Doctors can help prevent PHN

People who take anti viral drugs for shingles are much less likely to develop PHN. The benefit is greatest if a doctor prescribes anti viral drugs early in the outbreak of shingles, preferably in the first 2-3 days.

Anti viral drugs can be readily prescribed by Australian GPs. They include valaciclovir (Valtrex) and famciclovir (Famvir).

PHN can be treated

The symptoms of PHN can usually be managed with a variety of medications. These include:

• Strong pain killers such as codeine or oxycodone
• Tricyclic medications such as amitriptylline

In cases where PHN doesn’t respond quickly to treatment, the AHMF strongly recommends that patients attend a specialist pain management clinic.