The medical term for the sequelae of herpes zoster is “postherpetic neuralgia”. It is the most serious complication of varicella ⁃zoster virus (VZV) infection and is a common neuropathic pain. It occurs in the elderly, and postherpetic neuralgia occurs in >50% of patients with shingles over 60 years of age.
Most scholars believe that the virus enters the body through the mucous membrane of the whistle tract, spreads through the bloodstream, and appears on the skin as chickenpox, but most people do not develop chickenpox after infection, which is an insidious infection and becomes a carrier of the virus. Thereafter, the virus is latent in the dorsal root ganglion of the cremaster nerve and sensory ganglion for a long time, and when the body resistance is low, the virus is reactivated and spreads along the sensory nerve distribution area to form herpes zoster (HZ), resulting in central and peripheral nerve damage.
Clinical symptoms.
The onset of the disease is preceded by localized burning pain in the skin, accompanied by mild fever, fatigue, weakness, and other systemic symptoms. However, there can be no prodromal symptoms, and after 1-3 days, scattered erythema appears on the skin one after another. After 1-3 days, scattered erythematous patches of skin appear one after another, followed by clusters of corn- to green-bean-sized papules on the erythematous patches, which rapidly turn into blisters. The blister walls are tense and shiny, the blister water is clarified, and there are small depressions on most of the blister surface. After a few days, the blisters become cloudy and pus-filled, break down to form a vesicular surface, and finally dry and crust over, leaving a temporary erythema after the scabs fall off. In most patients with herpes zoster, after 3 to 4 weeks of treatment, the rash basically subsides, the nerve fibers are repaired, the pain disappears, and clinical cure is achieved. However, in older patients, because of the body’s reduced ability to repair and heal, the nerve fibers cannot be repaired for a long time, resulting in significant local pain that lasts for more than 1 month and is considered postherpetic neuralgia. In rare cases, the herpes virus can disperse to the anterior horn cells of the crista medullaris and visceral nerve fibers, causing motor nerve palsy, such as ocular and facial nerve palsy, as well as symptoms of the gastrointestinal and urinary tracts.
The distribution of herpes is mostly located on one side, non-columnarly in a band, and sometimes occasionally beyond the midline of the trunk, due to nerve endings crossing the midline. The thoracic, cervical and facial trigeminal nerve distribution areas are the preferred sites. Usually only one branch of the trigeminal nerve is involved. Local lymph nodes are often enlarged and painful. Neuralgia is the main symptom of the disease. The acute stage is due to inflammatory reaction of the ganglion, and the late stage neuralgia is caused by post-inflammatory fibrosis of the ganglion as well as the sensory nerves. Sometimes there is severe neuralgia before the appearance of herpes, when it is often misdiagnosed as acute abdomen or angina pectoris, etc. Elderly frail patients or patients with lymphoma often have sequelae of neuralgia, which can sometimes last for months.
How to confirm the diagnosis of herpes zoster.
(i) The pain is on one side of the body.
(ii) The pain is a throbbing stabbing pain.
(iii) The pain is not fixed at the site.
④ a feeling of fever in the painful area.
(5) The pain increases at night from 12:00 to 3:00 a.m. because the herpes virus is “time-sensitive”.
Four major characteristics
(1) Eosinophilia (i.e., preference for the thick fibers of the peripheral skin of the nerve, which exposes the nerve line and is the root cause of post-neuralgia).
2. wandering nature, leading to a rash that may appear elsewhere when repeated.
3. heat-loving, the worse the rash is when applied hot, it is advisable to apply cold.
4. time-recognition, with strong activity at 12-3 pm at night, so it is easy to wake up from pain in the middle of sleep.
Treatment.
Systemic treatment: antiviral treatment, nerve nutrition, pain relief, anti-inflammatory, etc.
Treatment of pain: Postherpetic neuralgia is caused by the erosion and destruction of the nerves by the virus that remains in the body. The occurrence of postherpetic neuralgia is related to the prediagnosis of herpes zoster and the lack of timely and correct treatment.
Electrical stimulation of the crestal nerve to shield the pain.
The patient is anesthetized locally while awake, a needle is punctured from the crest, and an electrode is implanted through the needle core outside the crestal medulla for electrical stimulation of the nerve; this method can reduce pain by 70-90% or even make it disappear completely. This technique is very minimally invasive and is used for most pain patients for whom medication is ineffective or who cannot tolerate the side effects of medication.