Severe pain from a common condition

If you or someone you know has had shingles you may be at risk of developing post herpetic neuralgia (PHN) - the most common complication of shingles that can sometimes be difficult for you recognise.

Shingles is a skin rash that runs in a linear fashion on the skin, along the distribution of a nerve. It can present anywhere on the skin, but usually occurs on the trunk, limbs and face. However, it never occurs on the palm or sole of feet.

Shingles is sometimes termed 'snake' infection in the Chinese community with the myth that patients would die if the snake meets its own tail, forming an entire ring around the body, squeezing and suffocating the patient. Hence the treatment prescribed by Chinese folklore is to burn the head of the snake.

In fact, shingles skin rash is caused by the Varicella zoster virus - the same virus that causes chickenpox. After a chickenpox infection, the virus remains dormant in the nervous system and can be reactivated by triggers such as stress or immune deficiency. When the virus reactivates and come out of its dormant state, it would cause pain, itch and a rash with fluid-filled blisters.

Shingles infection is as contagious as that of chickenpox. It will spread as a form of chickenpox infection to those who do not have any prior exposure to the chickenpox virus. Shingles do not affect those who already had chickenpox infection previously. It does not reactivate the virus dormant in the nervous system of individuals.

Shingles would usually occur in individuals with low immunity. Age, cancer, poor nutritional state, long term chronic illness, prolong steroid use and HIV patients are all susceptible to shingles infection. Interestingly, stress is also a risk factor for shingles outbreak.

Most patients with shingles have a disease course as that of chickenpox. After three weeks, most of the rash would disappear and recover.

Post Herpetic Neuralgia (PHN)

Fortunately most patients with shingles would experience the painful rash only for a few days. However, 15 – 20 per cent of patients may have to bear the burden of persistent shingles pain. This pain lasts even after the shingles rash has disappeared. This is a nerve-type pain. This complication of shingles is due to the destruction of the nerve that the virus has infiltrated, from which it was re-activated. It is also known as Post Herpetic Neuralgia, i.e. nerve pain after herpetic infection.

Signs and symptoms

Look out for signs and symptoms

If you have had shingles you should be on the lookout for certain signs and symptoms of PHN.

Firstly the pain from PHN is different from that of inflammatory pain such as fractures, bruises or sprains. It can be characterised by three distinct types of nerve pain and is often reported as episodic intermittent sharp, shooting pain in the background of constant aching or burning pain, together with extreme skin sensitivity to non-painful stimulus such as a light breeze or touch. It does not respond well to standard painkillers such as Panadol. The pain is excruciatingly distressing in the presence of numbness over that affected area of the body. It will last for days and weeks without any resolution in sight. That painful area does not allow anything to be touching it.

Some examples are:

Patients with PHN over the trunk cannot have clothes over their back or trunk. Tight clothing will trigger the painful area and cause a flare of pain. Patients with PHN over their legs find the blanket covering their legs extremely uncomfortable and painful. Patients with PHN over the face/forehead, cannot wash their face or forehead without being in tears.

In some instances, there may be muscle weakness or even paralysis in some cases. Very often, the pain is associated with insomnia, chronic fatigue, depression and weight loss. This is not surprising as the pain from PHN can even make individuals suicidal.

Those at risk of PHN would be increasing age, female gender and significant painful rash initially. If the shingles rash was very painful at the start, there is a greater likelihood that the pain will persist to become PHN.

Can PHN be treated?

If PHN is diagnosed and treated early and appropriately, the overall prognosis of PHN is moderately good. The rate of recovery declines with increasing number of months the patient has had the condition - for example, the outlook is poor for any patient with more than 2 years history of PHN.

Treatment of PHN is not the same as treating headache, injury or infection. Anti-inflammatory medications are not useful. Hence, it is not surprising that many PHN sufferers may have tried many therapies without any success and can take at least six months to a year before receiving the appropriate treatment.

It is important that you see your healthcare professional as soon as possible if you suspect you have PHN. There are a range of treatment options available, including oral, topical and combination therapies.

Dr Bernard Lee is the director of The Paincare Center, Paragon Medical Suites.