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Post-Herpetic Neuralgia
Post Herpetic Neuralgia (PHN) is the most common complication of Herpes Zoster-Varicella
(
HZV).  Pain is sustained for at least 90 days after the rash.  It occurs in approximately 20% of
patients with
HZV & 80% of cases occur in patients 50 years or older.
Last Updated 20th April 2020
Photos of Oro-Facial Herpes Zoster-Varicella Infections
What is Post-Herpetic Neuralgia (PHN)?

PHN is caused by nerve damage secondary to an inflammatory response induced by viral replication within a nerve.

PHN pain is typically discretely localised, intermittent, chronic & sufficiently intense to interfere with sleep & other
normal daily activities.  Additionally, the pain may have an itching, burning, sharp, stabbing / throbbing quality.  
PMH
may be associated with allodynia / hyperalgesia.

Aggravating factors include light touch, such as the touch of clothing / standing in a shower.

Relieving factors may include barriers to touch.


Risk Factors

These include:

  • Older age
  • Severe prodrome / rash
  • Severe acute HZV pain
  • Ophthalmic involvement
  • Immunosuppression
  • Chronic conditions such as Diabetes Mellitus & Lupus
  • Symptoms of allodynia


How is Post-Herpetic Neuralgia diagnosed?

PHN can be difficult to diagnose as a patient with pain long after the acute HZV rash has cleared up may not
remember the rash or associate the current pain with it.

In the diagnosis of
PHN, routine questioning should attempt to identify the nature of the patient’s pain.

Pain following a documented episode of acute
HZV usually provides clear evidence for a diagnosis of PHN.


How is Post-Herpetic Neuralgia treated?

Pain-management strategies should focus on symptom-control.

Although some patients have complete resolution of symptoms after several years, others have to continue using  
medications indefinitely.

  • Capsaicin cream 0.075% cream 3 – 4x daily
  • Lidocaine medicated plasters 5% to use for 12 hours & rest for 12 hours
  • Antidepressants (Nortryptiline 10 – 125mg / day & Duloxetine 60 – 120mg / day)
  • Anticonvulsants (Gabapentin 300 – 600mg mg TDS & Pregabalin 150 – 300mg / day)
  • Tramadol 50 – 100 mg 4 – 6 hourly
  • Amantidine 100 mg BD for 2/52 – to be continued for another 2/52 if necessary

Referral to specialist clinics (Oral Medicine & Oro-Facial Pain clinics).
Management of Post-Herpetic Neuralgia
Differential Diagnosis:

The differential diagnosis includes:

  • PHN
  • Impetigo
  • Candidiasis
  • Contact dermatitis
  • Insect bites
  • Auto-Immune blistering diseases
  • Dermatitis herpetiformis
  • Drug-related eruptions



Useful Websites:


The British Pain Society

Pain Concern

Pain UK

Trigeminal Neuralgia Association

Orofacial Pain Project