Post Herpetic Neuralgias: Epidurals, Paravertebral Blocks and more!

Summary

In this episode of the Pain Exam Podcast, Dr. David Rosenblum provides a comprehensive review of herpes zoster and postherpetic neuralgia (PHN), focusing on pathophysiology, diagnosis, and treatment options. Dr. Rosenblum explains that postherpetic neuralgia affects approximately 25% of patients with acute herpes zoster, causing debilitating unilateral chronic pain in one or more dermatomes. He discusses the three phases of herpes zoster: acute (up to 30 days), subacute (up to 3 months), and postherpetic neuralgia (pain continuing beyond 3 months). Dr. Rosenblum identifies risk factors for developing PHN, including older age, female sex, immunosuppression, prodromal pain, severe rash, and greater acute pain severity. He details the pathophysiology involving peripheral and central sensitization, and explains different phenotypes of PHN that can guide treatment approaches. For treatment, Dr. Rosenblum reviews various options including antiviral medications (which should be started within 72 hours of onset), corticosteroids, opioids, antidepressants (particularly tricyclics and SNRIs), antiepileptics (gabapentin and pregabalin), topical agents (lidocaine and capsaicin), and interventional procedures such as epidural injections and pulsed radiofrequency. He emphasizes that prevention through vaccination with Shingrix is highly effective, with 97% effectiveness in preventing herpes zoster in patients 50-69 years old and 89% effectiveness in those over 70. Dr. Rosenblum mentions that he's currently treating a patient with trigeminal postherpetic neuralgia and is considering a topical sphenopalatine ganglion block as a minimally invasive intervention before attempting more invasive procedures.

Chapters

Introduction to the Pain Exam Podcast and Topic Overview

Dr. David Rosenblum introduces the Pain Exam Podcast, mentioning that it covers painful disorders, alternative treatments, and practice management. He explains that this episode focuses on herpes zoster and postherpetic neuralgia as board preparation for fellows starting their programs, with ABA boards coming up in September. Dr. Rosenblum notes that he's not only preparing listeners for boards but also seeking the latest information to help treat his own patients with this notoriously difficult disease.

Upcoming Conferences and Educational Opportunities

Dr. Rosenblum announces several upcoming conferences including Aspen in July, Pain Week in September, and events with NYSIP and the Latin American Pain Society. He mentions he'll be teaching ultrasound and regenerative medicine at these events. Dr. Rosenblum invites listeners to sign up at nrappain.org to access a community discussing regenerative medicine, ultrasound-guided pain medicine, regional anesthesia, and board preparation. He also offers ultrasound training in New York and elsewhere, with upcoming sessions in Manhattan on July 12th and October 4th, plus private shadowing opportunities.

Overview of Postherpetic Neuralgia

Dr. Rosenblum defines postherpetic neuralgia as typically a unilateral chronic pain in one or more dermatomes after acute herpes zoster infection. He states that the incidence of acute herpes zoster ranges between 3-5 patients per thousand person-years, and one in four patients with acute herpes zoster-related pain will transition into postherpetic neuralgia. Dr. Rosenblum emphasizes that while this condition won't kill patients, it can be extremely debilitating and significantly reduce quality of life.

Treatment Options Overview

Dr. Rosenblum reviews treatment options according to the WHO pain ladder, including tricyclics like nortriptyline and antiepileptic drugs such as gabapentin. He explains that if pain is not significantly reduced, interventional treatments like epidural injections with local anesthetics and corticosteroids or pulsed radiofrequency of the dorsal root ganglion are options. For postherpetic neuralgia specifically, Dr. Rosenblum notes that preferred treatments include transdermal capsaicin, lidocaine, or oral drugs such as antidepressants or antiepileptics.

Phases of Herpes Zoster and Definitions

Dr. Rosenblum outlines the three phases during herpes zoster reactivation: acute herpes zoster-related pain (lasting maximum 30 days), subacute herpes zoster-related pain (pain after healing of vesicles but disappearing within 3 months), and postherpetic neuralgia (typically defined as pain continuing after 3 months). He mentions that acute herpes zoster pain often begins with prodromal pain starting a few days before the appearance of the rash.

Incidence and Risk Factors

Dr. Rosenblum states that the incidence of herpes zoster ranges between 3-5 patients per 1,000 person-years, with approximately 5-30% of cases lea