Postherpetic Neuralgia Prevalence and Treatment Approaches

After a bout of shingles, many people recover well and leave the pain of the condition behind. But not all. And for those who don’t, life can get — and stay — miserable.

One month after the onset of shingles  (which 1 in 3 people in the US experience in their lifetime, per the CDC), up to 14% of people develop this pain. That percent drops to 5% at the 3-month mark, when it is then viewed as chronic pain.¹

Anyone can develop PHN, but it is more likely to occur in immunocompromised and older individuals. It may add to the overall health miseries of older patients, who are more likely than younger patients to be coping already with other conditions.¹

“I probably see a case once a week to once a month,” said Narayan R. Kissoon, MD, assistant professor of neurology and anesthesiology at Mayo Clinic, Rochester, MN. “The pain persists and never goes away. Some can have a mild attack. But [in others] it can be pretty debilitating and have a major impact on their lives.” A lot depends, he said, on which nerves are affected.

Most often, those affected by PHN have a lancinating and burning pain in a unilateral dermatomal pattern, persisting 3 or more months after the initial herpes zoster (HZ) infection.¹

The thoracic region, the back, even the face can be affected, Dr. Kissoon said.

Causes of PHN

VZV lays dormant in the ganglia of certain central and peripheral nerves after the varicella episode resolves. As the immune system competency declines, and age increases, the result may be reactivation of the virus. As the virus replicates and travels down the axons, it reaches the skin. Blistering, erythema, and local inflammation occur.¹

In the majority of people, a history of rash with blisters in a dermatomal pattern is found. There may be other symptoms: burning pain, allodynia, paresthesia, dysesthesia, and pruritis.

If there is no rash, the patient may have zoster sine herpete (ZSH), a more complicated condition that affects the CNS on many levels.¹

Beyond vaccination, early recognition and treatment is advised once shingles occurs. Shingles treatment may decrease the risk of developing PHN.

Dr. Kissoon described his approach to treatment this way: “Trial and error, less invasive to more invasive, less expensive to more expensive.”

He tells patients, “We’re going to try conservative [treatments] first.”

Conservative Treatments

Among the options for treatment, old and newer, data show evidence for:

• skin patches: lidocaine patches or capsaicin skin patches may help relieve pain²
• antiviral medications: research has found that taking antivirals within 72 hours of developing a rash lessens the chances of getting PHN²
• anticonvulsants: anti-seizure medications, including gabapentin (Gralise, Horizant, Neurontin) and pregabalin (Lyrica) can reduce the pain²

Injections into the intrathecal or epidural area may help; evidence is not consistent, however.

A recent case report found high-frequency 10-k Hz spinal cord stimulation (SCS) yielded an 85% to 90% reduction in pain symptoms scores and a significant improvement in quality of life in a 70-year-old man who had an episode of herpes zoster 6 months prior. Lead tips were placed at the midline and paramedial side of the top of the T1 vertebral body after sensory confirmation testing in the middle of the placed lead found 100% overlapping pain areas.⁴

Although the one-week trial was successful, the patient deferred a permanent implant until he retired, to allow for postop recovery time.

Another treatment for PHN is dorsal root ganglion stimulation (DRG), which can specifically target the affected area. DRG is a version of SCS in which the leads are placed to stimulate the dorsal root ganglion, a small bundle of nerves near the spinal cord, not the spinal cord itself.

“In recent years, the interventional options and specific nuances of different spinal cord and peripheral nerve stimulation techniques have become a known positive force in the treatment pathway [for PHN],” said Karina Gritsenko, MD, an anesthesiologist and interventional pain physician at Montefiore Health System in New York, whose colleagues reported the dorsal root ganglion stimulator case histories.

For peripheral nerve stimulators, a trial of about a week is typically done first, using a temporary lead, said Dr. Kissoon. Goals are set, typically a 50% improvement in pain severity on a numeric scale. If a score of about 8 of 10 goes down to 4 of 10, for instance, a permanent device can be implanted.

Several studies have evaluated botulinum A toxin (BTX-A) for PHN, showing some success, Dr. Kissoon said. He cautioned, however, that the injections can be uncomfortable, and the treatment needs to be repeated often, every 12 weeks or so.

In one study, researchers from China treated 58 PHN patients with BTX-A and reported that attack frequency, duration, and severity were all significantly lower after treatment (P < 0.01). Painkiller use also declined (P < 0.01) and adverse reactions with the injections were few.⁶

A combination of therapies is often needed to relieve the pain, Dr. Kissoon said. “Goals are to cut the pain in half,” he said. Becoming pain free is usually not achieved, he cautions patients. However, he said, he does have some patients who are ‘’pretty close to pain free.” And they are, obviously, grateful.

REFERENCES