Postherpetic Neuralgia

oPatientPlus articles are written by UK doctors and are based on research evidence, UK and European Guidelines. They are designed for health professionals to use, so you may find the language more technical than the condition leaflets.

Postherpetic neuralgia (PHN) is the most common complication of herpes zoster (shingles). It produces chronic pain along cutaneous nerves and often some distortion of sensation. The pain can either persist after the acute episode of shingles or it can recur in an area previously affected by shingles.

There is a separate article on herpes zoster, entitled Shingles.

  • There are various definitions for PHN with regards to time of onset and duration of pain. This makes estimates about its prevalence difficult.
  • The incidence in UK primary care is thought to be about 3 per 1,000 person-years.[1] 
  • In England and Wales there are thought to be 225,000 new cases per year.
  • Approximately 20% of people will experience PHN after the initial rash has cleared.[2]
  • It is uncommon in children.

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Factors that may predispose to PHN include:[3] 

  • Older age (>50 years).
  • Female sex.
  • Presence of severe pain during the attack of shingles.
  • A more extensive and severe rash from shingles.
  • The presence of a prodrome (48-72 hours of throbbing pain and paraesthesia in the region of the affected sensory nerve before the shingles rash develops).
  • Psychosocial factors may predispose to PHN.
  • The site of the herpes lesion:
    • Risk of PHN is low in the jaw, neck, sacral, and lumbar regions.
    • Risk is moderate in the thoracic area.
    • The highest risk is in the trigeminal area, especially the ophthalmic division, and also the brachial plexus.

Research is currently underway looking at biomarkers that can help to identify those at risk of developing PHN.

  • Herpes zoster presents initially with a painful vesicular eruption in a single dermatome.
  • The eruption resolves but in PHN, pain continues. Definitions vary for the length of time the pain should persist, between 30 days and 4 months.
  • Pain is intense and may be described as burning, stabbing, shooting or throbbing.
  • The affected area may be itchy.
  • There may be allodynia. This is when pain is produced by stimuli that are not usually painful - eg, a cold draught or heat, or light touch.
  • Hyperalgesia may be present. This is where there is increased sensitivity to painful stimuli.
  • Pain can be debilitating. It can interfere with sleep, activities of daily living, and can also be so severe that it leads to depression and social isolation.[3][4]
  • Symptoms may be present for a few months or even years.[3]

Examination

  • The area affected by shingles may show some scarring.
  • There may be either hypersensitivity or reduced sensation in affected areas.
  • Allodynia may be demonstrated.

The diagnosis is usually clinical and no specific investigations are indicated.

General advice

  • Explain the nature of the condition to the patient, including expected duration of symptoms and aims of treatment.
  • Advise the patient to wear loose clothing and, next to the skin, cotton. This will cause less irritation.
  • Cling film or a plastic wound dressing may help to protect sensitive areas.
  • Cold packs may help to ease pain (unless there is associated allodynia made worse by cold).

Pharmacological

  • Start with paracetamol or a paracetamol/codeine combination.
  • If there is severe pain at the outset or if the above measures are not sufficient, add in either a tricyclic antidepressant (off-licence) or gabapentin (licensed) which have been shown to be effective in the treatment of PHN.[5]
    • Tricyclic antidepressants:
      • Amitriptyline (most widely used), imipramine, or nortriptyline may be used.
      • Care should be taken, especially in the elderly, due to the possibility of anticholinergic side-effects which can lead to acute confusion or cardiac arrhythmias.[3]
      • Initial dose is 25 mg at night (10 mg if elderly/frail).
      • Increase by weekly increments of 25 mg (10 mg if elderly/frail) until pain is controlled or side-effects occur.
      • Maximum dose is 75 mg at night (50 mg if elderly/frail).
    • Gabapentin:
      • Start with 300 mg once daily on day one, 300 mg twice daily on day two, and 300 mg three times daily on day three.[5]
      • Then increase the dose by 300 mg daily every two to three days according to the response.
      • Maximum dose is 3600 mg. This dose should be achieved over a minimum period of three weeks. Slower titration may be needed for patients such as the elderly or frail.
  • High-concentration capsaicin (8%) patch can be used topically if other treatments have not worked, are not appropriate or at a patient's request.[6] 
  • Topical lidocaine 5% patches may be considered if oral or other topical treatment is not suitable or is not tolerated. They are not recommended as first-line treatment. A Cochrane review found limited evidence for their effectiveness.

When to refer to a specialist pain clinic

  • The above treatment does not control pain after four to six weeks.
  • There are adverse effects of medication that are affecting/limiting treatment.
  • When considering the use of strong opioids or carbamazepine.
  • Most patients with PHN will experience a slow improvement over a long period of time, particularly when medical management is used.
  • There is a small group failing to show any improvement despite medical treatment.
  • No treatment has been shown to prevent PHN completely.
  • Antiviral therapy started within 72 hours of onset of the shingles rash may reduce the incidence of PHN.
  • Studies have shown that giving older people (adults aged over 60) varicella-zoster vaccine boosts their waning immunity and significantly reduces the morbidity due to herpes zoster and PHN.[7] It is safe and well tolerated.[8] A universal vaccination programme for 70-79 year-olds will be introduced from September 2013.[9] 
  • The introduction of a childhood varicella-zoster vaccine (as in the USA) will reduce the risk of herpes zoster, and therefore PHN, when this cohort of children becomes elderly. However, there is concern that reducing the number of children with varicella zoster by introducing a vaccine could lead to a short-term increase in herpes zoster in those who are latently infected.

Further reading & references

  1. Pinchinat S, Cebrian-Cuenca AM, Bricout H, et al; Similar herpes zoster incidence across Europe: results from a systematic literature review. BMC Infect Dis. 2013 Apr 10;13(1):170.
  2. Tyring SK; Management of herpes zoster and postherpetic neuralgia. J Am Acad Dermatol. 2007 Dec;57(6 Suppl):S136-42.
  3. Wareham DW, Breuer J; Herpes zoster. BMJ. 2007 Jun 9;334(7605):1211-5.
  4. Schmader K; Herpes zoster and postherpetic neuralgia in older adults. Clin Geriatr Med. 2007 Aug;23(3):615-32, vii-viii.
  5. Neuropathic pain - pharmacological management, NICE Clinical Guideline (March 2010)
  6. Derry S, Sven-Rice A, Cole P, et al; Topical capsaicin (high concentration) for chronic neuropathic pain in adults. Cochrane Database Syst Rev. 2013 Feb 28;2:CD007393. doi: 10.1002/14651858.CD007393.pub3.
  7. Tseng HF, Smith N, Harpaz R, et al; Herpes zoster vaccine in older adults and the risk of subsequent herpes zoster JAMA. 2011 Jan 12;305(2):160-6.
  8. Simberkoff MS, Arbeit RD, Johnson GR, et al; Safety of herpes zoster vaccine in the shingles prevention study: a randomized Ann Intern Med. 2010 May 4;152(9):545-54.
  9. Millions more protected against disease through improved vaccination programme; Dept of Health, April 2013

Disclaimer: This article is for information only and should not be used for the diagnosis or treatment of medical conditions. EMIS has used all reasonable care in compiling the information but make no warranty as to its accuracy. Consult a doctor or other health care professional for diagnosis and treatment of medical conditions. For details see our conditions.

Original Author:
Dr Michelle Wright
Current Version:
Peer Reviewer:
Dr Adrian Bonsall
Last Checked:
02/05/2013
Document ID:
2639 (v25)
© EMIS