Background: Varicella-zoster virus (VZV) is a member of the Herpesviridae family. It is the etiologic agent of varicella (chickenpox), the primary infection, and herpes zoster (HZ), the reactivation.

Herpes zoster ophthalmicus (HZO) involves the tissues innervated by the ophthalmic division of the trigeminal nerve and accounts for 10-25% of all cases of shingles. The sequelae of HZO can be devastating and include chronic ocular inflammation, visual loss, and debilitating pain.

Herpes zoster oticus (HZ oticus) involves the inner, middle, and external ear. HZ oticus presents as excruciating otalgia with an associated cutaneous vesicular eruption (external canal and pinna). When there is associated facial paralysis, the disease is called Ramsay Hunt syndrome.

Pathophysiology: After primary infection, VZV enters the dorsal root ganglia (trigeminal--HZO; geniculate--HZ oticus), where it remains latent for the lifetime of the individual.

The frequency of dermatologic involvement in HZ is similar to the centripetal distribution of the initial varicella lesions. This pattern may suggest that the latency arises from contiguous spread of the virus during varicella from infected skin cells to sensory nerve endings with subsequent ascent to the ganglia. It also may suggest that the ganglia are infected hematogenously during the viremic phase of varicella and that the frequency of the dermatome involvement in HZ reflects the ganglia most often exposed to reactivating stimuli.

Immunopathology

Specific antibodies (immunoglobulins G, M, and A) appear more rapidly and reach higher titers during reactivation (HZ) compared to the primary infection in immunocompetent patients.

HZ cutaneous rash appearance coincides with a profound VZV-specific T-cell proliferation. Interferon alpha production appears with HZ resolution. Note that a long-lasting, enhanced, cell-mediated immunity response to VZV exists.

Frequency:

• In the US: Primary infection: More than 90% of the population will be infected by adolescence; approximately 100% will be infected by 60 years.

  HZ: Of all individuals, 10-20% will be infected during their lifetime; approximately 131 per 100,000 person-years in Caucasians.

  According to Pavan-Langston's review, 1 million consults for HZ occur per year. Of these, 250,000 patients develop HZO. A subset of 50% of these patients develop HZO complications.

  Ramsay Hunt syndrome is the cause for as many as 12% of all facial paralyses.

Mortality/Morbidity:

• In the US, as many as 10,000 hospitalizations and approximately 100 deaths per year occur as a result of complications from VZV infection. The morbidity and mortality of patients with HZ are associated mostly with immunosuppressed individuals, including elderly persons, individuals who are immunosuppressed (ie, HIV, AIDS), persons on immunosuppressive therapy, and persons with primary infection in utero or in early infancy.

• In HZO, complications may be associated with inflammatory changes (infiltrative, eg, keratitis; or vasculitic, eg, episcleritis/scleritis, iritis, ischemic papillitis, orbital vasculitis). Other complications occur as a result of nerve damage (neurotrophic keratitis, some ocular motor palsies, and neuralgia) and tissue scarring (lid deformities, neuralgia, and lipid keratopathy).

• Ramsay Hunt syndrome usually causes more severe symptoms than Bell palsy. In numerous studies, only 10-22% of individuals with significant facial paralysis had complete recovery. Although, in one report, 66% of patients with incomplete paralysis had complete recovery.

Race: In 1995, Schmader et al reported that the lifetime incidence of HZ in Caucasians is twice that of African Americans.

Sex: No known gender predilection exists.

Age:

• Primary infection with VZV is a childhood disease.

• VZV reactivation or HZ is primarily a disease that affects healthy older adults.

• Incidence increases with age, peaking in the seventh decade of life.