Post-Herpetic Neuralgia

Clinical Scenario

Peter Wood, 55, presents face-to-face with ongoing pain after shingles. He had herpes zoster affecting the right T6 dermatome 10 weeks ago, treated with aciclovir. The rash has resolved but the pain persists — he describes burning, shooting pains and severe allodynia (pain from light touch, such as clothing against his skin). Co-codamol and ibuprofen are not helping. The pain is affecting his sleep, work (he cannot wear his work uniform comfortably), and his relationship with his wife.

What This Case Tests

Diagnosing post-herpetic neuralgia based on the timeline and pain characteristics; distinguishing neuropathic pain from nociceptive pain; initiating first-line neuropathic pain treatment per NICE guidelines; explaining why conventional analgesics are ineffective for neuropathic pain; assessing and addressing the functional and psychosocial impact.

Common Mistakes Trainees Make

The three most common mistakes are: continuing to prescribe conventional analgesics (paracetamol, NSAIDs, codeine) which are largely ineffective for neuropathic pain, not recognising the allodynia as a characteristic neuropathic feature, and failing to address the functional impact — Peter's sleep, work, and relationship are all affected, and each needs to be part of the management plan.

The Consultation Challenge

Peter has post-herpetic neuralgia (PHN) — neuropathic pain persisting more than 3 months (or in some definitions, 90 days) after shingles rash resolution. The pain is characteristic: burning (constant neuropathic background pain), shooting (lancinating nerve pain), and allodynia (pain from normally non-painful stimuli like clothing touching the skin). Co-codamol and ibuprofen are not working because they target nociceptive pain pathways, not neuropathic ones.

Start by validating Peter's experience. Chronic pain after shingles is common but often underrecognised. Peter may have been told the pain would resolve when the rash cleared, and the persistence feels alarming. Reassure him that PHN is a recognised condition with effective treatments.

Explain why his current painkillers are not working. Neuropathic pain is caused by damaged nerve fibres sending incorrect pain signals to the brain. Standard painkillers (paracetamol, NSAIDs, opioids) work on a different pain pathway and have limited effect on nerve pain. This explains Peter's frustration — it is not that his pain is imaginary, but that he has been given the wrong treatment.

Initiate first-line neuropathic pain treatment per NICE. Options include: amitriptyline (start 10mg at night, titrate up to 75mg — preferred if sleep is affected, which it is), duloxetine (if amitriptyline is not tolerated), gabapentin (titrate from 300mg to maximum 3600mg daily), or pregabalin (titrate from 75mg to maximum 600mg daily). Given Peter's sleep disturbance, amitriptyline is a logical first choice as it has sedative properties at low doses that can aid sleep alongside pain control.

Address the allodynia practically. Loose clothing, cotton fabrics, and desensitisation techniques (gradually exposing the area to touch) can help. Some patients find topical capsaicin cream (0.075%) or lidocaine 5% patches helpful — these are second-line options if systemic treatment is insufficient.

Assess the functional impact comprehensively: sleep (how many hours? Is he avoiding the affected side?), work (can he wear his uniform? Is he taking time off?), and the relationship (how is the pain affecting intimacy and mood?). Each of these needs to be part of the management conversation.

Time check: Spend the first 3 minutes on pain history and assessment. By minute 5, explain why current analgesics are ineffective. Initiate neuropathic treatment between minutes 6-9. Address the functional impact between minutes 10-11. Use the final minute for titration plan and follow-up.

How Examiners Mark This Case

Data Gathering and Diagnosis: Examiners assess whether you characterise the pain as neuropathic (burning, shooting, allodynia, hyperalgesia — in a dermatomal distribution following shingles) and distinguish it from ongoing infection or other causes. They look for a functional impact assessment covering sleep, work, and relationships, and review of current medications including why they are ineffective. Screening for mood disturbance (chronic pain and depression are closely linked) demonstrates holistic assessment.

Clinical Management and Medical Complexity: Examiners expect first-line neuropathic treatment initiation per NICE CG173: amitriptyline, duloxetine, gabapentin, or pregabalin. They look for a clinical rationale for the choice (amitriptyline for sleep disturbance), a clear titration plan with starting dose and target dose, explanation of expected timeline (2-4 weeks for initial effect), and awareness of second-line options (topical capsaicin, lidocaine patches, combination therapy). Stopping the ineffective conventional analgesics demonstrates medication review skills.

Relating to Others: Examiners assess whether you validate Peter's experience (his pain is real, the previous treatment was wrong for this type of pain), explain the neuropathic mechanism in accessible language, and address the functional impact with practical advice. Peter should leave understanding why he has been suffering, confident in the new treatment plan, and feeling that someone has finally taken his pain seriously.

Example Opening

Strong opening: "Hello Peter, I can see the pain from your shingles hasn't gone away. That must be really frustrating, especially when the rash itself has cleared up. Can you describe exactly what the pain feels like now?"

When explaining neuropathic pain: "The reason the painkillers you've been taking aren't working is that this is a different type of pain — it's nerve pain, not the kind of pain that paracetamol or codeine are designed for. The shingles virus has damaged the nerve fibres in that area, and they're now sending pain signals when they shouldn't be. The good news is there are medications that specifically target this type of pain, and they work much better."

Avoid: "Shingles pain can last a while — give it time and it should settle." (Dismissive and inaccurate — PHN at 10 weeks requires active treatment).

How This Appears in the SCA

PHN tests your knowledge of neuropathic pain management — a distinct area from standard pain management. Examiners assess whether you can distinguish neuropathic from nociceptive pain, initiate appropriate treatment, explain why conventional analgesics fail, and address the holistic impact. This is a common and clinically important SCA topic.

Key Statistic

Post-herpetic neuralgia develops in approximately 10-20% of shingles patients, with risk increasing significantly with age. The shingles vaccine (Shingrix) reduces PHN risk by approximately 90%. Amitriptyline, gabapentin, and pregabalin are effective first-line neuropathic pain treatments, with NNT (number needed to treat) of approximately 3-5.

Relevant Guidelines

• NICE CG173: Neuropathic pain in adults — pharmacological management
• NICE NG126: Shingles — management guidelines
• NICE quality standard on neuropathic pain.

Frequently Asked Questions

What are the first-line treatments for post-herpetic neuralgia?

NICE CG173 recommends: amitriptyline (start 10mg at night, titrate to 75mg), duloxetine (60-120mg daily), gabapentin (start 300mg, titrate to 3600mg daily in divided doses), or pregabalin (start 75mg, titrate to 600mg daily). Choice depends on the patient's profile: amitriptyline if sleep is affected (sedative properties), duloxetine if co-existing depression, gabapentin/pregabalin for severe pain. Monotherapy first, then combination if needed.

Why don't standard painkillers work for neuropathic pain?

Neuropathic pain is generated by damaged nerve fibres sending abnormal signals — not by tissue injury (which is what paracetamol, NSAIDs, and opioids target). Standard analgesics act on nociceptive pain pathways in the peripheral tissues and spinal cord. Neuropathic pain requires modulation of nerve signalling through different mechanisms: sodium channel blocking (amitriptyline), calcium channel modulation (gabapentin, pregabalin), or serotonin-noradrenaline reuptake inhibition (duloxetine).

How long does it take for neuropathic pain medication to work?

Initial effect is typically seen within 2-4 weeks at an adequate dose. Full benefit may take 6-8 weeks with titration. Set realistic expectations: "You may notice some improvement in the first couple of weeks, but it usually takes a month or so to get the full benefit. I'll review you in 2-4 weeks to check how it's going and adjust the dose if needed." This prevents premature discontinuation.

What is allodynia and why is it significant?

Allodynia is pain from a stimulus that would not normally be painful — such as clothing touching the skin, a light breeze, or water from a shower. It is a hallmark of neuropathic pain and occurs because damaged nerve fibres misinterpret normal sensory input as pain. Recognising allodynia as a neuropathic feature (rather than dismissing it as exaggeration) demonstrates clinical knowledge and validates the patient's experience.

Should I discuss shingles vaccination for future prevention?

Yes — although Peter has already had shingles, the NHS shingles vaccination programme (Shingrix) is offered to eligible patients. Shingrix reduces the risk of shingles recurrence and PHN by approximately 90%. Check whether Peter is eligible based on the current vaccination schedule (offered from age 50 in most NHS programmes). Mentioning this demonstrates proactive preventive care.