====== Postherpetic neuralgia ======

Postherpetic [[neuralgia]] is a nerve pain.

The pain usually resolves after 2–4 weeks. When the pain persists > 1 month after the vesicular eruption has healed, this pain syndrome is known as postherpetic neuralgia (PHN). PHN can follow herpes [[varicella]] infection in any site and is difficult to treat by any means (medical or surgical). It can occasionally be seen in a limb and follows a dermatomal distribution (not a peripheral nerve distribution). PHN may remit spontaneously, but if it hasn’t done so by 6 mos this is unlikely.

===== Etiology =====
Postherpetic neuralgia (PHN) results from injury to the nerves system caused by [[varicella zoster virus]] during shingles infection
((Park H. G., Park P. G., Kim W. J., et al. Ultrasound-assisted mental nerve block and pulsed radiofrequency treatment for intractable postherpetic neuralgia: three case studies. Korean Journal of Pain. 2014;27(1):81–85. doi: 10.3344/kjp.2014.27.1.81.)).

The neuralgia typically begins when the herpes zoster vesicles have crusted over and begun to heal, but can begin in the absence of herpes zoster—a condition called zoster sine herpete (see [[Herpes zoster]]).

Patients with postherpetic neuralgia (PHN) always suffer persistent and severe breakthrough pain (BTP) which may arise from nerve changes virus affection or immune response. BTP is characterized by brief duration (median 30 min), a severe intensity, rapid onset (less than 3 minutes), and daily frequency (more than 4 episodes per day) 
((Zeppetella G., Ribeiro M. D. C. Pharmacotherapy of cancer-related episodic pain. Expert Opinion on Pharmacotherapy. 2003;4(4):493–502. doi: 10.1517/14656566.4.4.493.)).

===== Clinical =====
Typically, the neuralgia is confined to a dermatomic area of the skin, and follows an outbreak of herpes zoster (commonly known as shingles) in that same dermatomic area. 

===== Treatment =====

see [[Postherpetic neuralgia treatment]]