Postherpetic Neuralgia (PHN)

Definition

Postherpetic neuralgia is a chronic neuropathic pain condition that persists after the resolution of the rash caused by herpes zoster (shingles). It occurs due to nerve damage caused by the varicella-zoster virus reactivation.

Causes

• Reactivation of the varicella-zoster virus (which causes chickenpox) later in life leads to shingles.

• Nerve inflammation and damage during shingles can result in persistent nerve pain.

• PHN develops when the nerve damage does not heal properly after shingles rash and blisters disappear.

Symptoms

• Persistent burning, stabbing, or aching pain at the site where shingles rash appeared.

• Pain can be constant or intermittent.

• Increased sensitivity to touch or temperature (allodynia).

• Itching, numbness, or tingling sensations in the affected area.

• Pain can last months to years after the rash heals.

Risk Factors

• Older age (more common in people over 60).

• Severe shingles rash or prolonged rash.

• Delayed treatment of shingles.

• Immunocompromised status.

Diagnosis

• Based on history of shingles and characteristic persistent pain.

• Physical examination of affected area.

• Rule out other causes of neuropathic pain.

Treatment

Medical Treatments

• Antiviral drugs during acute shingles to reduce severity (acyclovir, valacyclovir).

• Pain medications:

  • Antidepressants (e.g., tricyclic antidepressants like amitriptyline)

  • Anticonvulsants (e.g., gabapentin, pregabalin)

  • Topical agents: Lidocaine patches, capsaicin cream

  • Opioids (used cautiously)

• Nerve blocks or steroid injections in severe cases.

Home Care and Supportive Treatments

• Applying cool compresses to reduce discomfort.

• Gentle skin care to avoid irritation.

• Psychological support or counseling for chronic pain.

Prognosis

• Many patients improve within a year.

• Some cases can persist for years causing significant impairment.

• Early treatment of shingles reduces the risk and severity of PHN.

Prevention

• Shingles vaccine (e.g., Shingrix) recommended for adults over 50 to prevent shingles and PHN.

• Early antiviral therapy during shingles outbreak.