I. Definition
Postherpetic neuralgia is a persistent pain with skin segmental changes even after acute herpes zoster has been cured. The sequelae of persistent pain for more than one month after clinical cure of acute herpes zoster are caused by the destruction of the posterior horn cells of the spinal cord by the herpes zoster virus and remain a world-class pain problem. It occurs mostly in the chest, followed by the jaw and face, waist and legs, and is one of the intractable pains that plague middle-aged and elderly people, and its duration is as short as 1 to 2 years or even more than 10 years in the long run. Patients suffer from long-term pain and suffering, not only with depression and low quality of life, but also with reduced or even lost work and social skills.
II. Pathogenesis
Postherpetic neuralgia is neuropathic pain, which is the result of peripheral nerve injury and is associated with changes in central nerve signal processing. The afferent nerves of the skin play a role in the pain of PHN, the virus causes damage to them, the peripheral neurons issue reduced electrical prevalence, the peripheral neurons respond to stimuli in an elevated manner, the axons are demyelinated, the terminal growth axon branch buds spontaneous discharge of peripheral nerves VZV activation leads to inflammation of the dorsal root ganglion, important changes in the pathways of the central nervous system to feel the injury make the afferent nerves blocked, these changes lead to abnormally high activity of pain signaling neurons in the CNS.
III. Pain characteristics of PHN
Most patients with PHN complain of the following different types of pain and sensory abnormalities: drilling pain, stabbing pain, flashing pain, burning pain, electric shock-like pain, abnormal pain, pain that gradually increases in response to repeated stimuli, sensory hypersensitivity, and unbearable itching.
1, dull pain: persistent at the skin scar, almost complete loss of skin sensation in that innervated area, no elongated pain; pain in the residual part of the skin, complete or incomplete absence of temperature sensation.
2, allodynia: PHN site, when receiving some non-painful stimuli in daily life, such as touch, temperature sensation reduced by the slightest contact stimulus can induce pain, is one of the representative clinical symptoms of PHN, PHN makes injury receptors should be acutely hyperactive.
3, post-herpeticitch (PHI): is the scratching after HZ is often the only symptom after HZ.
IV. Diagnosis.
1, medical history: previous history of acute herpes zoster whose pain persists for more than 1 month after 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, the nature of pain: pain is mostly sudden slash-like or lightning-like episodic pain or persistent burning pain, 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, or even loss of confidence in life and suicidal tendency.
V. Treatment
Three-step treatment program.
①Medication.
② Non-invasive local treatment.
③ Minimally invasive local treatment.
1.Pharmacological treatment
(1) Tricyclic antidepressantsTCAs
Amitriptyline (amitreptyline), amitriptyline is an effective sodium channel blocker, the mechanism of action is to enhance the degree of inhibition of spinal neurons involved in the sensation of pain by inhibiting the re-extraction of norepinephrine and 5-hydroxytryptamine, not only can improve the state of inhibition, due to the mechanism of the drug itself to inhibit pain, the efficacy of up to 50%. Side effects include confusion, urinary retention, postural hypotension, and cardiac arrhythmias.
(2) Anti-epileptic drugs carbamazepine, phenytoin sodium, gabapentin (Gabapentin), gabapentin main mechanism is to reduce the conduction of glutaminergic nerves, combined with voltage-dependent this ion channel, to prevent the inward flow of calcium ions.
(3) Anti-arrhythmic drug lidocaine, 0, 5mg/kg/hour, intravenous drip; slow rhythm 150-300mg/day, divided into three oral doses.
(4) Antitussive drug acylamizine, effective for wandering pain of PHN.
(5) Narcotic analgesics: can be used to reduce pain, but the effect is not good.
(6) Application of local anesthetics: 5% lidocaine ointment or gel or patch for more limited neurogenic pain of the skin, which is more effective for allodynia.
(7) Chinese medicine, Chinese herbal medicine / Chinese and Western medicine / acupuncture, etc., Chinese herbal medicine treatment principles: dispel the wind, pass the ligament, relieve pain, and at the same time to help
(8) Metacycline: This drug is a non-thiourea H2 receptor antagonist. It has immune restoring and antipruritic effects and has antiviral effects and is used only for this disease. Each time 200mg, 3 times a day, add 400mg at bedtime, symptoms control stop, no adverse reactions were seen.
2, non-invasive local treatment: ultra-laser, ultrasonic electroconductive drug transdermal absorption therapy.
3.Minimally invasive local treatment
(1) Nerve block: selective nerve block according to the sensory innervation area of the lesion, which can immediately relieve the severe pain in the original lesion area, but the effect is short-lived and needs to be repeated several times.
Epidural cavity block: single or continuous block, puncture site depends on the lesion site, the drug is 2% lidocaine or 0, 25% bupivacaine injection, the drug solution can be added to hormonal drugs, some add 2-3mg morphine, etc.
(2) Blood cupping: if it does not pass, it is painful, using a trigeminal needle to prick the local skin, negative pressure cupping to drain the black and purple blood, once a week. Small trauma, obvious analgesic effect.
(3) Sympathetic nerve block or radiofrequency treatment: radiofrequency needle puncture reaches the ganglion next to the vertebrae, specifically blocking the burning pain and skin hypersensitivity pain: the mechanism is to use the detectable temperature to act on the ganglion, nerve trunk, nerve root and other parts, causing protein coagulation and denaturation, blocking the conduction of nerve impulses to achieve the purpose of pain relief. It is a kind of physical nerve destructive therapy, which has developed from blocking the trigeminal nerve to treating all neuralgia.
(4) Injection of polymolecular activated oxygen to adjust the nerve by injecting the triple oxygen molecule formed by the combination of three oxygen atoms into the damaged nerve root: to play the role of local anti-inflammation, analgesia and nerve nutrition.
(5) Radiofrequency ablation of spinal nerve roots, which has failed to relieve pain by various methods, is destroyed by radiofrequency high temperature to stop the pain of the nerve conduction.
4.Psychotherapy.
While strengthening the treatment of pathological factors, psychological intervention should be actively carried out to interrupt the vicious cycle of pain-depression-pain-severe depression and prevent the occurrence of suicidal tendencies.