Indonesia
What is Post-Herpetic Neuralgia?
Herpes zoster (HZ) results from reactivation of latent varicella-zoster virus in dorsal root ganglion neurons. The most common complication of HZ is post-herpetic neuralgia (PHN), which is characterized by persistent neuropathic pain in the affected dermatome after the rash resolves. PHN is characterized by a unilateral, stabbing/burning pain in a dermatomal pattern that persists for three months or more after the onset of the herpes zoster (HZ) outbreak. Two universally accepted risk factors for HZ are increasing age and immunosuppression, and HZ is a major risk factor for the development of PHN. Currently, multimodal management is essential, with some researchers/clinicians focusing on prevention in high-risk populations rather than cure due to the debilitating and often refractory nature of PHN. Treatment modalities for PHN primarily include drug therapy and physical therapy. Post-herpetic neuralgia is defined as neuropathic pain that occurs after the eruptive phase of herpes zoster as the most common clinical sequelae. Post-herpetic neuralgia (PHN) is a chronic neuropathic pain syndrome characterized by chronic, persistent, and often severe pain following reactivation of the varicella-zoster virus (VZV) (herpes zoster) in the sensory ganglia of the cranial nerves or dorsal root ganglia of the spinal cord. To date, the definition of PHN has been inconsistent across studies, with incidence ranging from ≥1 to ≥6 months after the rash. Compared with acute HZ-related pain (pain preceding or accompanying visible skin manifestations), which resolves within a month, PHN can persist for months or even years.
Several risk factors for PHN have been reported, including advanced age, female sex, severe immunosuppression, severe rash, and acute pain from zoster episodes. Physical comorbidities, such as autoimmune conditions and diabetes, may also be associated with an increased risk of PHN.
The diagnosis of neuropathic pain is based on the typical symptoms and findings of neuropathic pain, particularly the combination of minus symptoms (sensory deficits such as hypaesthesia, hypalgesia) and plus symptoms (burning pain, especially at rest, throbbing pain, allodynia, hyperalgesia). The history of HZ and the nature of the pain are critical parameters in the diagnosis of PHN. The medical history serves to differentiate the pain syndrome (nociceptive or nociceptive vs neuropathic). It should provide information about relevant lesions or diseases of the peripheral or central somatosensory system. Information about disorders, previous medications, and pain-related comorbidities such as anxiety, depression, or sleep disorders is also important. The patient's history may reveal conditions that may help differentiate the diagnosis of PHN, including a recent history or presence of herpes simplex virus, impetigo, candidiasis, contact dermatitis, insect bites, autoimmune blistering disease, dermatitis herpetiformis and drug-related eruptions. In about 50% of patients with PHN, dynamic mechanical allodynia occurs in the pain-producing area in response to normally painless stimuli, such as light touch. Thermal hyperalgesia occurs in about one-third of patients. However, in some cases, decreased sensation or numbness may be experienced by patients. Complementary quantitative sensory testing may provide additional information about the functional status of the somatosensory system. The intensity and quality of pain should be assessed using an appropriate pain scale, based on the patient's ability to communicate such as a numeric rating scale (usually an 11-point scale: from 0, no pain, to 10, severe pain), a visual analog scale, or a verbal descriptor scale (eg, McGill Pain Questionnaire). The fact that pain affects quality of life should be evaluated, usually by interview, but structured questionnaires can also be used. In children, a Likert scale consisting of 4-5 verbal descriptors or Icons can be used.
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