Post-Herpetic Neuralgia (PHN)

🔍 When to Suspect

Persistent or recurrent pain in a dermatomal distribution, often described as burning, shooting, or stabbing, that continues for more than 3 months after the onset of a shingles rash

From the full topic in The Ocean Library: Post-Herpetic Neuralgia (PHN)

🧭 When to suspect

Post-herpetic neuralgia (PHN) is the persistence or recurrence of neuropathic pain in a dermatome previously affected by shingles (herpes zoster), continuing for more than 3 months after the onset of the acute rash. It is the commonest complication of herpes zoster and reflects damage to the affected sensory nerve by the reactivated varicella zoster virus (VZV) – it is not ongoing infection.

The pain is typically burning, stabbing, shooting or aching, confined to the original dermatome, and frequently accompanied by allodynia (pain provoked by light touch such as clothing) or troublesome itch. It can be relentless, wrecking sleep, mood and daily function in an often elderly population. The three primary-care tasks are to recognise the neuropathic character, start an effective neuropathic agent early and titrate it, and exclude the small number of red-flag mimics.

Suspect PHN in an older patient with a past episode of shingles in the same area whose pain has outlasted rash healing. The strongest risk factors are increasing age, severe acute zoster pain, a severe or extensive rash, prodromal pain before the rash, ophthalmic (trigeminal) involvement, and immunosuppression.

Phase	Timing after rash onset	Terminology
Acute	Within 30 days	Acute herpetic neuralgia
Subacute	30–90 days (1–3 months)	Subacute herpetic neuralgia
Chronic	Persisting > 3 months (> 90 days)	Post-herpetic neuralgia (PHN)

Source: NICE CG173

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