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 1).
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) 2).
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.