Post-Herpetic Neuralgia

What is Post-Herpetic Neuralgia?

Post-herpetic neuralgia (PHN) is the most common complication of shingles. Shingles is a reactivation of the varicella-zoster virus, which lies dormant in sensory nerve ganglia after a primary chickenpox infection. When the virus reactivates, it travels down the nerve, causing the characteristic rash and acute pain. In most people this resolves within a month. In some, the nerve damage left behind triggers chronic pain that persists long after the skin has healed.

The mechanism is direct nerve injury: the virus damages the sensory nerve fibres in the affected dermatome, leading to abnormal pain signalling, loss of normal inhibitory function, and central sensitisation. The result is pain that bears no proportion to any ongoing injury. The thoracic dermatomes and the face (particularly around the eye, from ophthalmic shingles) are the most frequently affected regions. Risk increases significantly with age: PHN develops in fewer than 10% of patients under 40 but in up to 50% of those over 60.

Early treatment of the acute shingles episode reduces but does not eliminate the risk of PHN. Once established, PHN is treatable but can be difficult to resolve completely in older patients.

Symptoms

• Burning, stabbing, or aching pain along the path of the original shingles rash
• Allodynia: pain triggered by light touch, clothing contact, or a gentle breeze on the skin
• Hypersensitivity or, paradoxically, areas of numbness within the painful region
• Itching that feels more like pain than itch
• Pain limited to one side of the body within one or two dermatomes
• Fatigue and sleep disruption driven by the constant or paroxysmal pain

How We Treat It

First-line medications include low-dose antidepressants (amitriptyline, duloxetine), gabapentinoids, and topical lidocaine or capsaicin patches. When these provide insufficient relief, interventional approaches targeting the nerve directly produce better results. Sympathetic nerve blocks, particularly intercostal nerve blocks for thoracic PHN or stellate ganglion blocks for facial involvement, reduce central sensitisation and give pain-free windows that can persist well beyond the duration of the local anaesthetic.

Epidural steroid injections in the affected dermatome are another option: they reduce residual neuroinflammation in the nerve root and often improve the response to topical and systemic medication. We combine procedures with optimised medical management because the two approaches work synergistically: the nerve block reduces the pain load enough for the medications to work at lower, more tolerable doses. Most patients see meaningful improvement; in a proportion, the pain resolves entirely.