Interview with Professor Wang Yong: Diagnosis and treatment strategies for postherpetic neuralgia (1)

1.
Postherpetic neuralgia is age-related, and the incidence of postherpetic neuralgia is directly proportional
to age.
For example, the incidence of postherpetic neuralgia may be 60% in patients aged 60 years, 70% in patients aged 70 years, and 80% in patients by 80 years
of age.
Therefore, the first difficulty in the treatment of postherpetic neuralgia is age, the older the age, the worse the treatment effect, and the easier it is to leave postherpetic neuralgia
.

2.
Postherpetic neuralgia is a kind of nerve damage
from the perspective of pathophysiological mechanism.
Every adult has shingles virus in the body, usually mainly lurking in two parts, the first is the trigeminal meniscus, and the second is the dorsal root ganglia
next to the spine.
Usually shingles is latent in these two ganglia, once the immune is weak, such as cold, tumor, diabetes, mental or work pressure is relatively high, at this time the shingles virus will be activated
along the paraspinal nerve.

Nerves are similar to wires, there is a layer of wire skin called myelin sheath on the outside of the wire, and the copper wire in the middle is called axon, so the nerve is composed of
myelin sheath and axons.
Herpes zoster virus is a neurotropic virus that directly engulfs the myelin sheath
after the onset of the herpes zoster virus.
Similar to wires, if the wire skin on the outside of the wire is bitten, the copper wire of the wire is exposed, which is equivalent to the axon being exposed, and once it rains, you can see the wire sparks
.
The herpes zoster virus is a neurotropic virus that destroys the nerve myelin sheath, causing axons to be exposed
.
Most of the human internal environment is made up of water, and once the myelin sheath is damaged and the axons are exposed, any stimulation will make the nerves fire, causing pain
.

However, there are currently very few drugs for the treatment of nerve repair, and the only recognized effective may be methylcobalamin
.
It can also be combined with vitamins, but methylcobalamin to promote nerve repair is still difficult
.
Methylcobalamin may have a repairing effect on the myelin sheath, but there is currently no specific drug
to promote the repair of the entire nerve.
So this is a difficult point to treat, because all neurological diseases, including diabetic peripheral neuropathy, peripheral nervous system disease, spinal cord injury, nerve damage after repair is very difficult
.

3.
Postherpetic neuralgia is typical neuropathic pain
.
Pain is generally divided into two categories, the first is nociceptive pain, such as a needle prick and sudden avoidance, which is nociceptive pain; The second type is neuropathic pain, i.
e.
nerve damage caused by herpes zoster or diabetic peripheral neuropathy, which is typical neuropathic pain
.

Neuropathologic pain has two pathophysiological mechanisms
.
The first is peripheral nerve sensitization, and the second is central nerve sensitization
.
Peripheral nerve sensitization, that is, after nerve damage, ordinary touch can cause pain
.
After peripheral nerve pain, secondary ascending conduction of the central nervous system will occur, causing central nerve sensitization
.
Therefore, the pathophysiological basis of neuropathological pain is peripheral nerve sensitization, and the second is central nerve sensitization
.

In summary, the treatment difficulties are mainly three aspects, the first age factor, the second nerve damage, and the third pathophysiological mechanism
.
From these three aspects, postherpetic neuralgia is still very difficult to treat
.

Yimaitong:

The treatment of postherpetic neuralgia has always been a hot spot and difficulty in research, and there are various ways to treat postherpetic neuralgia.

Wang Yong

professor

First, drug treatment
.
(1) Calcium ion antagonists, in fact, are blockers of calcium channels, mainly including pregabalin, which is also an antiepileptic drug, which is currently the first-line drug
for the treatment of postherpetic neuralgia.
The mechanism of action is to inhibit calcium influx, there are calcium ions inside and outside the cell, calcium influx will promote nerve cell discharge, resulting in increased
pain.
Therefore, pregabalin is currently the first choice for the treatment of postherpetic neuralgia, as well as the same type of gabapentin
.

(2) Lidocaine gel plaster, a sodium ion antagonist, mainly blocks sodium influx, and is currently also a first-line drug
for the treatment of postherpetic neuralgia.
Some guidelines consider it to be a second-line medication
.
The mechanism of action is to block sodium influx, reduce nerve discharge, and reduce central and peripheral nerve sensitization
.

(3) Antidepressants
.
Antidepressants are most commonly used with dual-channel duloxetine
.
At present, many studies have found that pain and depression, the pathogenesis is common, caused by nerve destruction, so antidepressants also have a therapeutic effect on
pain.
Therefore, international guidelines use many antidepressants, including amitriptyline and duloxidine, as first-line drugs
for the treatment of neuropathic pain.
But there is a reality that foreign patients may be better medically compliant, and antidepressant patients can accept
it.
However, in domestic clinical practice, unless the onset of shingles is very long, there is no choice to use antidepressants, patients may be acceptable, so most patients are not easy to accept
the use of antidepressants for neuralgia.
In addition, antidepressants have a longer
onset of action for neuralgia.
With pregabalin for neuropathic pain, the pain may be quickly reduced in an hour or two, but it may not work until two weeks after using antidepressants, so many patients are difficult to accept
.

So basically the drugs used now are pregabalin, lidocaine gel plaster, and rarely use antidepressants
.
These are the three commonly used drugs at present, and the others belong to the second-line and third-line drugs
.
Second-line drugs include nonsteroidal analgesics, and third-line drugs include opioids, but they are not recommended for the treatment of postherpetic neuralgia
.

Second, physical therapy
.
The most commonly used physical therapy is transcutaneous electrical stimulation, a neuromodulation that uses nerve stimulation to treat postherpetic pain
.
However, physical therapy alone may not be effective as an adjunct to pharmacotherapy, and postherpetic neuralgia may not be effective
.

Third, nerve block therapy
.
Nerve block treatment is currently mainly used with trioxygen, the first has an anti-inflammatory effect, because neuropathic pain is actually neuroinflammation; The second can improve microcirculation, including promoting nerve repair
.
So now mainly use trioxygen
.
Sometimes hormones are also used, which also have anti-inflammatory and promote cell growth and nerve repair effects
.
Therefore, after the onset of herpes zoster, the sooner nerve block treatment is used, the better the prognosis, and the occurrence of postherpetic neuralgia
will be reduced.
Therefore, it is currently recommended that if the pain is obvious, nerve block therapy
should be used as soon as possible.

Fourth, high-voltage pulsed radiofrequency and electrical spinal cord stimulation/peripheral nerve stimulation
.
(1) High-voltage pulsed radio frequency is a kind of neural regulation, the principle of action is to directly insert the radio frequency needle into the dorsal root ganglia, through electrical stimulation to regulate the nerve.

There are two principles of high-voltage pulsed radiofrequency, the first can promote nerve repair, and the second can relieve pain
.
Therefore, this is currently the most effective invasive treatment for postherpetic neuralgia
.
(2) Peripheral nerve electrical stimulation is only used for the first trigeminal nerve or supraorbital nerve
.
Frontal shingles, which can be treated by electrical stimulation by installing an electrode above the eyebrows to treat herpes
zoster of the supraorbital nerve when it does not heal for a long time.
Electrical stimulation of the spinal cord is to place electrodes into the spine and then electrify through the spine, one is to inhibit pain conduction, and the other is to regulate the nerves and promote nerve repair
.
In cases where other methods have not worked, spinal cord stimulation
may be considered.