Shingles/Post Herpetic Neuralgia
This is a chronic pain syndrome brought about by reactivation of the varicella zoster virus (chicken pox). After primary infection it lies latent in nerve cell bodies, i.e.,, dorsal root ganglionDRG, cranial nerve, or autonomic ganglion of the host, normally contained by competent T-cell immunity. With aging, T-cell immune responsiveness to VZV declines. The virus replicates fully and spreads along neural tissue within a dermatome. Nearly all older adults are latently infected with VZV, with the lifetime incidence estimated to be 20-30% in general population and up to 50% of people living until the age of 85. Overall, it affects 1 million people per year in the US. It often affects the thoracic dermatomes (50-70%), but also cranial, cervical, lumbar (10-20%), and the sacral (2-8%) dermatomes.
Characteristic features of neuropathic pain in dermatomal areas, mainly sensory nervous system involvement, and absence of radiologic finding distinguish PHN from other pathologies. PHN should be considered in any patient who has a history of chicken pox illness and presents with severe pain. Risk factors for developing PHN include increasing age, greater severity of acute pain, greater severity of rash, and prodromal pain. The pain is often described as a burning, aching, throbbing pain. The patient may also have paroxysms of stabbing or shooting pain. While most PHN resolves within one year of the resolution of the rash, it can and often does last for years and cause substantial suffering and reduction in quality of life. The goal of treatment includes reduction of pain and associated symptoms including depression, insomnia, and functional impairment. Most commonly used therapies for treatment of PHN include tricyclic antidepressants and antiepileptics including gabapentin and pregablin, lidocaine patch, andas well as opioid analgesics. Treatment depends on patient comorbidities, patient preference, cost, and formulary restrictions.
In summary, post-herpetic neuralgia is a disease that is very common and can be treated aggressively with medication management to reduce pain, long term suffering and disability.