Postherpetic neuralgia (PHN) is the sequelae of acute herpes zoster that persists in pain for more than one month after clinical cure. It is caused by the destruction of the posterior horn cells of the spinal cord by the herpes zoster virus and remains a world-class pain problem. It occurs mostly in the chest, followed by the jaws and face, and can also involve the waist and legs. It is one of the intractable pains that plague the middle-aged and elderly, and its duration is as short as 1 to 2 years, or even more than 10 years in the longest cases, with a general history of up to 3 to 5 years without effective pain control methods. Patients suffer from chronic pain, which not only leads to depression and poor quality of life, but also reduces or even loses the ability to work and socialize.
Postherpetic neuralgia (PHN) is a common clinical condition in the pain department, with the incidence of herpes zoster ranging from 1.4 to 4.8 per 1000 of the population, with a tendency to increase gradually. About 10% of patients with herpes zoster can have postherpetic neuralgia, and the incidence of postherpetic neuralgia is highest in elderly patients over 60 years of age, reaching 50%-75%. As the population ages, the incidence of herpes zoster and postherpetic neuralgia will increase significantly, with more than 80% of patients having pain during the acute phase of herpes zoster.
Clinical manifestations of postherpetic neuralgia
Postherpetic neuralgia is most often seen in people with low immunity and in the elderly and frail, and it is not uncommon for neuralgia to persist six months or more after the herpes zoster has subsided.
When the ophthalmic branch of the trigeminal nerve (fifth cerebral nerve) is involved, it may involve the cornea and affect vision.
Some patients are afraid to wear clothes in order to reduce clothing irritation, and some patients hold up their clothes from time to time in order to avoid painful attacks caused by clothing irritation. This pain hypersensitivity reaction, some of them also show spontaneous pain, no thing touching the affected part also often occur pain. Some patients suffer a lot of mental and psychological damage because of the pain, even if they can’t eat and sleep at night. Other patients are emotionally overwhelmed by the chronic pain, and some are depressed and desperate.
Post-herpetic neuralgia pathogenesis
The pathogenesis of postherpetic neuralgia (PHN) is still unclear, but based on the clinical manifestations and pathological studies during the onset of herpes zoster, it can be broadly summarized as the following three aspects.
I. Peripheral neuropathy
Peripheral neuropathy and herpes zoster neuralgia can be caused during the onset of herpes zoster.
Central nerve abnormalities
Because one of the complications of herpes zoster is aseptic meningitis, it means that herpes zoster may also involve the central nervous system while causing peripheral neuropathy. The persistence of postherpetic neuralgia despite clinical treatment of refractory postherpetic neuralgia with neurogenotomy may also suggest a central cause. Altered function of the thalamus on pain modulation loops may be an important cause of chronic pain.
Diagnostic basis for postherpetic neuralgia
Postherpetic neuralgia is generally diagnosed on the basis of the following.
1. medical history: previous history of acute herpes zoster with pain persisting for more than 1 month after its clinical cure.
2. local symptoms: there are obvious abnormalities of sensation, pain, and touch distributed according to the innervation area, and there may be local pigmentation changes.
3. Nature of pain: the pain is mostly sudden cut-like or lightning-like episodic pain or persistent burning pain or tight bundle-like pain.
4.After-effects: There are obvious after-effects of nerve injury in the affected area, such as itching, tightness, ankylosis, twitching or other discomfort.
5. Psychological abnormalities: patients have heavy psychological burden, depression, and even lose confidence in life and have suicidal tendencies.
The nature of postherpetic pain and hazards of shingles
After the disease due to improper treatment, often can remain serious herpes neuralgia, light stimulation immediately cause pain attacks, some patients to reduce clothing stimulation, even dare not wear clothes.
Some patients even hold up their clothes from time to time to avoid painful episodes caused by clothing irritation
Some patients are hypersensitive to pain, and pain occurs from time to time even if nothing touches the affected area.
some also exhibit spontaneous pain.
some patients suffer great mental and psychological damage due to pain, even not being able to eat or sleep at night.
Patients are emotionally overstressed due to chronic pain, and some are depressed and desperate.