Postherpetic neuralgia (also known as shingles) is an acute, painful, viral infection resulting from an endogenous activation of the varicella virus (an infection that remains latent in the spinal sensory ganglia and cranial nerves).
This virus has the particularity of being specifically human and is responsible for three clinical bodies: chickenpox, herpes zoster and postherpetic neuralgia.
The severity and complications increase with age and depend on the immunity created by the virus. This immunity may be altered by vaccination and/or herpes zoster-specific immunoglobulin. The diagnosis is clear: the patient complains of unilateral spinal radicular pain, almost always in the dorsal area.
Concomitantly or hours after the pain, a rash (blisters or vesicles) appears on the affected dermatome (area of skin innervated by a nerve root) that persists for two to four weeks. In addition to vesicles, patients experience a heat sensation, numbness or tingling in the affected area, pain, itching, fever and chills, among others.
The most frequent complications of herpes zoster are cutaneous (bacterial infections), visceral (hepatitis, pericarditis, cystitis, pancreatitis) and neurological (postherpetic neuralgia is the most frequent), meningoencephalitis, transverse myelitis, paralysis of peripheral and cranial nerves and ocular complications.
Histopathological studies in the acute and subacute phases of herpes zoster showed the presence of inflammatory infiltrates in the ganglion of the nerve and nerve bundles. Follow-up studies led to the conclusion that, in herpes zoster, the intensity of pain, fever, extension of the rash and the presence of important sensory deficits are risk factors for the onset of postherpetic neuralgia, not forgetting that the greatest and most consistent risk factor is age. It appears predominantly in elderly patients.
Generally speaking, the pain associated with shingles begins before or at the onset of the rash and persists for days or weeks until it disappears or becomes permanent. In some cases, the pain may appear years after the initial episode, usually caused by an injury in the same location. The type of pain in postherpetic neuralgia is variable and can be spontaneous or provoked. In a clinical evaluation, it is only possible to distinguish by the skin rash.
The types of pain caused by herpes zoster or postherpetic neuralgia varies, can appear spontaneously, or be provoked. The therapeutic approach to herpes zoster/postherpetic neuralgia includes antiviral medication, antidepressants, anti-inflammatory drugs and opioids. In very disabling, resistant and long-lasting situations, nerve root block is also possible.
Finally, it is important to know that the virus is transmitted by direct contact through the vesicles, or by indirect contact with contaminated objects. The contagious period can last up to two weeks and the incubation period is two to four days after contact with the infected person.
Given the unpredictability and diversity of the various types of pain, postherpetic neuralgia remains one of the most intriguing types of pains observed in clinical practice, although it is known that the most effective treatment is aggressive therapy in the acute phase, especially in the elderly.
Article submitted by the HPA Group
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