Key Points
ÎPostherpetic neuralgia (PHN) is a painful aftermath of Herpes zoster (HZ, "shingles"). Acute HZ occurs when dormant varicella zoster virus is reactivated in ganglia and travels down sensory nerves to infect the skin in the involved dermatome.
ÎCommon sites for shingles outbreaks are the thorax and face, usually in the ophthalmic division of the trigeminal nerve.
ÎZoster can occur without a rash during the early phase; the absence of a rash and vesicles does not signify that the pain is not due to zoster (zoster sine herpete).
ÎThe most important risk factors for PHN are older age (>60) and severe acute pain with acute shingles.
ÎPHN occurs following shingles in 5-15% of patients but occurs ~3x more often among those over age 60.
ÎBeing immunocompromised raises the risk of having HZ and then PHN.
ÎPatients with PHN commonly describe a constant generally burning pain, and intermittent pain with lancinating or shooting quality. Brush-induced allodynia is observed in nearly 90% of cases.
ÎAll persons 60 years and older should receive a zoster vaccination.
> In the Shingles Prevention Study, zoster vaccine reduced the incidence of PHN by 66.5%. > Lifetime risk of developing acute HZ is as high as 40% - 50% of those over 50 years and 80% of those over 80.
ÎImmunizing children against chicken pox prevents HZ in later life.
ÎOral acyclovir, famciclovir, and valacyclovir reduce acute pain and the duration of chronic pain in older patients who have HZ and are treated within 72 hours of rash onset, but even optimally treated patients can develop PHN.
Shingles Image courtesy of Wheatgrass Pty. Ltd.
