The Rash Healed and the Burning Did Not: Inside Post-Herpetic Neuralgia

What this video covers

• Why shingles damages the dorsal root ganglion and how that turns into post-herpetic neuralgia
• How rogue nerve firing and sodium-channel changes are thought to drive burning, shock-like nerve pain
• What happens during the procedure, step by step, under fluoroscopy or ultrasound with contrast
• What the randomized evidence does and does not show about preventing post-herpetic neuralgia
• How long relief usually lasts, why the evidence sits in the first weeks after the rash, and why repeat blocks for long-standing post-herpetic neuralgia have no support
• What safety steps lower the risk of nerve injury when corticosteroid is injected
• MEDICAL DISCLAIMER: This content is for educational purposes only and is not medical advice. It does not substitute for professional diagnosis or treatment. Always consult a licensed healthcare provider regarding your condition. Viewing this video does not establish a doctor-patient relationship.

Shingles pain persists after the rash heals because the virus damaged nerve cell bodies in a dorsal root ganglion beside the spinal cord, not the skin. That is post-herpetic neuralgia: hurt nerve cells firing on their own. The loss of large touch fibers is the leading explanation for why a bedsheet feels like an injury.

The rash healed months ago, and everyone keeps pointing that out. Your skin looks almost normal now. Yet you sleep in a recliner, because you cannot stand the weight of a bedsheet on that one band of skin. A shirt seam. The draft from a car window. And under the burning, jolts — electric and without warning — while you sit perfectly still. That is not skin that failed to heal. It is a nerve cell body that a virus attacked and that did not fully survive. This article covers where the damage really is and why it causes just the symptoms you have. It covers what a selective nerve root block can and cannot do about it. And it covers what the randomized evidence honestly shows.

What causes post-herpetic neuralgia?

The varicella-zoster virus you met as a child never left your body. It hid in the dorsal root ganglia — clusters of sensing nerve cell bodies that sit in a bony opening beside your spinal cord. It stayed there, silent, for decades.

When cell-mediated immunity (the T-cell arm of your defenses) thins with age or illness, the virus wakes up inside one ganglion. It travels down that ganglion’s nerve fibers to the skin. That is why the rash was a band: a band is the skin turf of one ganglion. The rash is the visible end of the trip. The real damage is at the start of it, upstream, next to your spinal cord.

What the virus does there is not gentle. Human autopsy studies show hemorrhagic ganglionitis — bleeding inside the ganglion — and loss of the large myelinated fibers leaving it. Myelin is the coating that makes a nerve fiber fast, like insulation on a wire. The large, well-coated fibers normally carry plain touch and vibration. Those are the fibers that drop out. (Established: human autopsy pathology.)

Animal nerve-injury models then show more. The surviving pain fibers, the nociceptors, make more sodium channels and start firing ectopically — going off on their own with nothing touching them at all. That rogue firing is inferred to drive sensitization (a turned-up volume) in the dorsal horn of the spinal cord. Be precise about that step. It is animal work, and the inference has not been shown in humans. (Inferred mechanism.)

Why does post-herpetic neuralgia make light touch hurt?

Two of your symptoms come directly out of that picture.

The spontaneous burning is damaged nerve cells firing on their own. Nothing is touching you. The signal starts inside a nerve that can no longer stay quiet. That is why it ignores what you are doing. It is why it shows up while you sit still. And it is why it is worst at the times of day with the least to distract you.

The allodynia — the light touch of fabric felt as injury — is harder to explain. The honest answer is that we have a leading explanation, not a proven one. The leading explanation is that losing those large myelinated fibers wears down the wiring that separates touch from damage. When the fast touch channel is stripped out, the nervous system loses part of what it uses to tell the two apart. Then ordinary contact gets read as harm.

That is a leading explanation, not a proven mechanism, and not the only one. Some patients show the opposite picture: a patch of skin that is numb and painful at the same time. Any full account has to explain that too. (Contested: mechanism of post-herpetic allodynia is not settled.)

What this does mean is that your symptom is not made up, and it is not in your head. It is the expected result of a specific, documented injury in a specific place.

How is post-herpetic neuralgia diagnosed?

This is where a careful exam earns its keep, because several conditions cause a band of pain. Only one of them is post-herpetic neuralgia.

• Radicular pain from a disc is also dermatomal — it follows a single nerve root’s skin turf. But posture and load usually set it off, and it often brings a weaker reflex.
• Intercostal neuralgia after a broken rib follows the same band from a totally different cause.
• Length-dependent polyneuropathy, the kind that comes from diabetes or chemotherapy, hits both sides alike in a stocking shape. It ignores a single band, and that difference matters a great deal for what follows.
• Zoster reactivation without any rash is a known condition. It is considered when the pain fits but there was never a rash.

Sorting this out is mostly done by hand, not by machine. A soft brush and a cold metal probe, drawn across the skin, map whether the abnormal zone stops at a dermatomal border — the edge of one nerve root’s turf — or ignores it. Strength and reflexes are tested. Imaging is ordered when the picture stops acting like one dermatome, not by habit at the start.

Two failures that put people in the recliner

Standard care for shingles is often good care. Antivirals started inside seventy-two hours are the right call. Most people who get shingles do not end up with lasting pain. But two specific failures keep happening, and they run in opposite directions.

The first failure is time. The randomized evidence for nerve blocks in shingles lives in the first weeks after the rash. Patients are told, correctly, that this fades in most people. Then nobody sets a date to see them again. Pain bad enough to predict post-herpetic neuralgia gets treated as something to wait out. By the time a referral is written, the window the trials studied has closed. Waiting is not a neutral act.

The second failure runs the other way. Someone with burning in both feet from diabetes or chemotherapy is offered a single nerve root block. A block treats one root, one side, one strip of skin. A polyneuropathy is failing every long nerve fiber in both legs at once. Offered without a reason in the anatomy, that is not treatment — that is scheduling.

Symptom-control medication has a real role here, and so does desensitization work (slowly retraining the skin to accept touch). Neither one repairs a damaged ganglion. Neither one tells you which structure is making your pain. Do not start, stop, or change any medication without consulting your physician.

What is a selective nerve root block for shingles pain?

The target is the nerve root as it exits the foramen, the bony opening in the spine. That spot sits right next to the ganglion the virus damaged.

One difference often gets blurred, and it matters. A selective nerve root block places a small amount of medicine outside the foramen, on the root itself. A transforaminal injection drives medicine through the foramen into the epidural space, where it spreads above and below. Different spread, different risks, different studies. What we describe here is the extraforaminal (outside the opening), selective version. In a moment you will read that no randomized trial studied it.

Two imaging tools do two different jobs. In the neck, ultrasound shows soft tissue that fluoroscopy (live X-ray) cannot. It shows the front and back bumps of the bone on the side of the vertebra, and the root sitting in the groove between them. Color Doppler scans the planned needle path before anything moves, because the vertebral artery lives in that neighborhood. But be exact about what Doppler does. It helps avoid a vessel. It cannot tell anyone that a needle tip has entered one. Only contrast dye, injected under live fluoroscopy, does that. And the neck carries the highest rate of unrecognized intravascular injection anywhere in the spine.

So ultrasound maps the anatomy and fluoroscopy confirms where the medicine goes, at every level. Contrast outlines the root sleeve before a single drop of nonparticulate steroid goes in. Rathmell and colleagues published a multidisciplinary consensus in Anesthesiology in 2015. They built it with the FDA Safe Use Initiative. They did it because rare but disastrous nerve injury — including stroke and spinal cord injury — has occurred with these injections. Nonparticulate steroid, live X-ray guidance and contrast checks are the steps that consensus names to lower that risk. (Established: consensus safety document. It is cited here for risk and technique, not for benefit.)

The step-by-step detail — positioning, imaging order, and what the day itself looks like — is on the selective nerve root block injection treatment page, alongside the broader range of image-guided nerve blocks used for different pain generators.

What the evidence shows — including what it does not

This is the part of the conversation that most often goes missing.

Blocks early in shingles reduce the incidence of post-herpetic neuralgia. Kim and colleagues, in the Korean Journal of Pain in 2017, meta-analyzed nine randomized trials. Nerve blocks applied within three weeks of rash onset shortened how long shingles pain lasted. They also lowered the rate of post-herpetic neuralgia at three, six, and twelve months. (Established, moderate-strength evidence — in acute herpes zoster.)

Now the fine print. Every line of it carries weight:

• Incidence, not severity. That result is about stopping the condition from setting in. It is not about easing pain in someone who already has it. If you already live with post-herpetic neuralgia, that study describes a door you have walked past.
• The benefit came from specific techniques. It came from paravertebral blocks and from continuous or repeated epidural blocks. Stellate ganglion block did not deliver it. A single epidural injection did not deliver it.
• None of those nine trials tested a fluoroscopically guided transforaminal or selective nerve root block. The technique described above was not the technique studied.

One placebo-controlled trial tested a root block directly, and hedged its own conclusion. Zheng and colleagues, in Pain Practice in 2019, randomized 140 patients with acute cervical shingles to ultrasound-guided cervical nerve root block or a matched placebo. The block cut the thirty-day burden of illness. It cut the use of other pain medicine and improved quality of life. There were no serious side effects. The authors’ own conclusion was that reducing post-herpetic neuralgia “might be feasible.” Feasible is their word, and we will not upgrade it here to proven. (Established for acute burden of illness; not established for post-herpetic neuralgia prevention.)

And the limits are firm. Anesthetic relief lasts hours. Steroid benefit usually lasts weeks to a few months. It is not permanent. Repeat blocks for long-standing post-herpetic neuralgia have no trial support at all. Nothing supports this procedure in diabetic or chemotherapy-induced polyneuropathy.

Can post-herpetic neuralgia be prevented?

Here is the part that does not sell a procedure.

Look at the pooled ZOE-50 and ZOE-70 trial data, reported in the New England Journal of Medicine in 2016. The recombinant zoster vaccine cut post-herpetic neuralgia by roughly 89 percent in adults seventy and older. Nothing done with a needle comes near that number.

That is prevention, not treatment — it does not help pain you already have. But if you are over fifty and have not had that vaccine, that talk matters more than this one. It matters most of all for people who have not had shingles yet.

Who this procedure is actually for

Two groups, stated plainly.

1. Acute or subacute shingles pain confined to one dermatome, still within weeks of the rash — where the randomized data lives and the clock is still ticking.
2. Single-level radicular pain where symptoms, examination, and imaging all name the same root — where the block works as a diagnostic tool. It confirms the pain source before a bigger decision is made. To be honest, the trials cited above were run in shingles, not in radiculopathy (pinched-nerve pain). This diagnostic use reflects clinical practice, not those trial results.

Everything else falls outside. A whole-body neuropathy, a pain that crosses a dermatomal border, a picture nobody has mapped — those are not candidates for this procedure. The right answer in the room is to say so.

Where metabolic disease is slowing nerve repair, blood sugar control gets addressed alongside any procedure. The reasoning: a nerve trying to heal in high blood sugar is working against itself. That is a practice approach, not a trial result for this condition. Individual results vary.

The risks, in full

This is a needle procedure next to a spinal nerve root. It carries real risk.

The most serious, though rare, is injection into a small artery. That can cause spinal cord infarction or stroke. In the neck, the vertebral artery is the main concern. Other risks include nerve injury, dural puncture (a hole in the spinal sac) with a spinal headache, a blood clot in the epidural space (epidural hematoma), infection or epidural abscess, short-term weakness or numbness, local anesthetic toxicity, and pneumothorax — a collapsed lung — at cervical and thoracic levels.

The common ones are less dramatic and more likely. They include several days of high blood sugar and a brief dip in adrenal function. A post-injection flare in the first day or two is common.

Patients on anticoagulant or antiplatelet medication need a plan for the procedure agreed in advance. Do not start, stop, or change any medication without consulting your physician.

An honest picture of a course of treatment

What follows is a composite — a picture built from many patients with this condition, not one person’s chart.

Someone arrives five weeks after a chest-wall rash healed. A burning band runs across the left ribs. Clothing is unbearable. Sleep comes only upright. Five weeks sits past the window where the data came from. They were told that going ahead was reasonable, not proven. An extraforaminal block was performed under live imaging with contrast and nonparticulate steroid. Blood thinners were held per plan.

The first two days were worse — a post-injection flare — and glucose climbed for a week. By the second week the allodynia eased enough to wear a shirt and lie flat. It was the first real sleep in two months. A nerve-pain medicine was raised slowly over six weeks, at the cost of some daytime dullness. Desensitization work was added — on purpose, brushing skin that hates being touched. A second block a month later gave less. That was a judgment call, named as one, because nothing supports repeating a block in established post-herpetic neuralgia. There was no third. A diminishing response is information.

At six months the pain was a fraction of where it started. Not absent.

And now the part we owe you. No one can say how much of that was the block, how much was the medicine and desensitization, and how much was six months passing. Post-herpetic neuralgia improves on its own in many people. No honest account of a single course can pull those threads apart. Individual results vary.

Frequently asked questions

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Key takeaways

• Post-herpetic neuralgia is not unhealed skin. It is damage to the dorsal root ganglion beside the spinal cord. Human autopsy shows hemorrhagic ganglionitis and loss of large myelinated fibers. The rogue-firing step is inferred from animal models, not shown in humans.
• Allodynia, where a bedsheet reads as injury, is best explained by the loss of those large touch fibers. That loss wears down the wiring that separates touch from damage. Leading explanation, not proven mechanism.
• The randomized evidence for nerve blocks sits in the first three weeks after the rash. It concerns incidence, not severity in established disease. It came from paravertebral and repeated or continuous epidural blocks. No trial in that review tested a selective nerve root block.
• A single nerve root block treats one root on one side. It is not a treatment for symmetric diabetic or chemotherapy-related neuropathy, and repeat blocks for long-standing post-herpetic neuralgia have no trial support.
• The strongest evidence in this disease is preventive: the recombinant zoster vaccine cut post-herpetic neuralgia by roughly 89 percent in adults seventy and older. If a rash has healed and the pain has not, the clock matters. Waiting is not a neutral act.

This article is educational and is not a substitute for evaluation, diagnosis, or treatment by a physician. Individual results vary. Do not start, stop, or change any medication without consulting your physician. To have a band of burning nerve pain properly mapped and localized before any procedure is scheduled, call (314) 481-5000 or text (314) 886-5902.

References

1. Kim HJ, Ahn HS, Lee JY, Choi SS, Cheong YS, Kwon K, Yoon SH, Leem JG. Effects of applying nerve blocks to prevent postherpetic neuralgia in patients with acute herpes zoster: a systematic review and meta-analysis. Korean J Pain. 2017 Jan;30(1):3-17. PMID 28119767. PubMed
2. Zheng S, Li X, Yang X, He L, Xue Y, Yang Z. Ultrasound-Guided Cervical Nerve Root Block for the Treatment of Acute Cervical Herpes Zoster: A Randomized Controlled Clinical Study. Pain Pract. 2019 Jun;19(5):500-509. PMID 30734476. PubMed
3. Rathmell JP, Benzon HT, Dreyfuss P, Huntoon M, Wallace M, Baker R, et al. Safeguards to prevent neurologic complications after epidural steroid injections: consensus opinions from a multidisciplinary working group and national organizations. Anesthesiology. 2015 May;122(5):974-84. PMID 25668411. PubMed

Medically reviewed by Dr. Gurpreet Singh Padda, MD, MBA, MHP — Board Certified in Anesthesiology, Pain Medicine, Interventional Pain Management, Addiction Medicine, and Obesity Medicine. Last reviewed July 2026.

Dr. Gurpreet Singh Padda, MD, MBA, MHP