Post Herpetic Neuralgia (PHN)

Post herpetic neuralgia (PHN) is the most common complication from shingles (varicella herpes zoster). It is a condition that is caused by damage to nerve fibres, causing burning pain that lasts long after the rash and blisters of shingles has resolved.

Symptoms

The symptoms of PHN are generally limited to the area of skin where the shingles outbreak occurred. This is most commonly a band around the chest/abdomen, and usually on one side of the body, but can occur anywhere, including the face and head. Other symptoms include:

• Persistent pain – often described as burning, sharp, stabbing, or deep and aching.
• Sensitivity to light touch (allodynia)
• Heightened sensitivity to painful stimuli (hyperalgesia)
• Itching and numbness – less common but may occur

The risk of postherpetic neuralgia increases with age, primarily affecting people older than 60 and those with weakened immune systems such as those with diabetes.

Over time, there is a slow resolution of the pain syndrome, but for a small group of patients, they will experience chronic pain as a result of the nerve damage and do not respond of medical treatment.

Diagnosis

Diagnosis is based on the patient assessment as well as known risk factors for PHN.

The criteria for diagnosis includes:

• Severe pain that continues for more than 1- 3 months in the same place that he shingles occurred, despite the rash having resolved
• Burning sensation on the skin, even with the slightest pressure
• Sensitivity to touch or temperature changes

In most cases, no further tests are necessary.

Treatment

Unfortunately, there is no treatment that modifies or alters the disease course of PHN. Treatment is more aimed at symptom control.

Symptom control for PHN can include:

Topical Medications

Medications applied to the skin can be used alone or in conjunction with oral medications. Topical medications include compounded creams that include the ingredients capsaicin, local anaesthetics such as lignocaine and anti-inflammatory. In addition, lignocaine local anaesthetic patches can be prescribed and are applied directly to the skin affected by the PHN to provide temporary pain relief. These patches are usually used for a period of 12 hours, then removed for 12 hours. The process can be repeated if needed and can be cut to size.

Oral Medications

Certain medications used to typically treat epilepsy or depression have been shown to lessen the pain associated with PHN. These medications include Gabapentin (Neurontin), Pregabalin (Lyrica), Amitriptyline or Duloxetine (Cymbalta). Opioids such as Endone, Palexia, morphine or tramadol have been shown to have little or no effect on the symptoms of PHN and should be used only under the direction of a pain specialist.

It is important to note that PHN affects people in different ways and one person’s response to treatment will be different from another person’s. Your pain specialist will work out a plan on how best to treat you and your symptoms.

**This information sheet has been written for patients affected by PHN and provides general information only**

References

• Pain Australia
• Mayo Clinic