View source for Postherpetic neuralgia

==Background==
[[File:Dermatoms alt.png|thumb|Sensory dermatomes by spinal level.]]
*Postherpetic neuralgia (PHN) is a complication of [[acute herpes zoster]] (AHZ), also known as "[[Shingles]]"
*While [[AHZ]] is usually painful, PHN refers to pain which becomes severe and persists after the vesicular lesions of [[AHZ]] are no longer forming. There is an overlap between acute zoster pain and PHN pain, and together they are sometimes referred to as Zoster Associated Pain. However, if pain persists beyond 3 months from time of vesicle formation it is termed PHN.
*PHN can be challenging to treat, and may require trials and titration of various therapies, usually in a primary care or neurology outpatient setting.
*Prevention of PHN by early antiviral therapy for [[AHZ]] is a cornerstone of ED management
*Prevention of shingles via childhood [[varicella]] vaccination and adult shingles vaccination, in a primary care setting is the single most important preventing step

==Clinical Features==
*Pain in the same unilateral dermatomal distribution of a recent [[shingles]] episode which becomes more severe after the vesicular phase of shingles
*Lancinating or burning pain which persists beyond 3 months after the [[shingles]] episode
*Scars may be evident from recent [[shingles]]
*Hypersensitivity, hypoesthesia, hyperalgesia or allodynia in the area.
*Autonomic dysfunction in the area (e.g. excessive sweating)

==Differential Diagnosis==
*Acute zoster pain (see [[Shingles]])
*[[Focal neurologic deficits|Other neuralgias and neuropathies (trigeminal, diabetic)]]
*Other causes of chest wall pain (e.g., [[rib injury]])
*Pleuritic [[chest pain]] ([[pulmonary embolism]], [[pneumothorax]],[[ pneumonia]])

==Evaluation==
===Workup===
*Typically, none
**If other differentials are considered, workup would be tailored to confirming or ruling out those processes

===Diagnosis===
*Typically a clinical diagnosis based on recent acute zoster plus ongoing symptoms.

==Prevention==
Treating shingles with antiviral therapy within 72 hours of rash appearance plays an important role in preventing the development of PHN. For immunocompromised patients, antiviral therapy should be initiated even after 72 hours.
Routine vaccination for varicella in childhood, and for shingles prevention in adulthood is the best prevention for shingles and PHN

==Management==
''Given that the pain is often difficult to control, much of the management will occur in a primary care setting, and will often involve trials and titration of multiple agents.''

===ED setting===
*Gabapentinoid, either [[Pregabalin]] or [[Gabapentin]]
*[[Lidocaine]] 5% patch
*For short term relief of acute pain exacerbation:
**[[Ketamine]] infusion
**IV [[lidocaine]] infusion

===Primary Care Setting===
*Tricyclic antidepressants (TCA)
*Topical capsaicin

'''Invasive'''
*Sympathetic blockage
*Spinal stimulators

==Disposition==
*Usually discharge home with pain management as described above.

==See Also==
*[[Shingles]]

==External Links==

==References==
<references/>
*J. Tang, Y. Zhang, C. Liu, A. Zeng, and L. Song, “Therapeutic Strategies for Postherpetic Neuralgia: Mechanisms, Treatments, and Perspectives,” Curr Pain Headache Rep, vol. 27, no. 9, pp. 307–319, Sep. 2023, doi: 10.1007/s11916-023-01146-x.
*E. Y. Gan, E. A. L. Tian, and H. L. Tey, “Management of herpes zoster and post-herpetic neuralgia,” Am J Clin Dermatol, vol. 14, no. 2, pp. 77–85, Apr. 2013, doi: 10.1007/s40257-013-0011-2.
*C. Gruver and K. B. Guthmiller, “Postherpetic Neuralgia,” in StatPearls, Treasure Island (FL): StatPearls Publishing, 2024. Accessed: May 08, 2024. [Online]. Available: http://www.ncbi.nlm.nih.gov/books/NBK493198/
*“Herpes Zoster Treatment & Management: Approach Considerations, Topical Treatments, Pharmacologic Therapy for Herpes Zoster,” Jun. 2023, Accessed: May 08, 2024. [Online]. Available: https://emedicine.medscape.com/article/1132465-treatment

[[Category:Neurology]]