Complications of varicella zoster virus reactivation

Varicella zoster virus (VZV) is an exclusively human neurotropic alphaherpesvirus. Primary infection causes varicella (chickenpox), after which virus becomes latent in ganglionic neurons along the entire neuraxis. With advancing age or immunosuppression, cell-mediated immunity to VZV declines and virus reactivates to cause zoster (shingles), which can occur anywhere on the body. Skin lesions resolve within 1-2 weeks, while complete cessation of pain usually takes 4-6 weeks. Zoster can be followed by chronic pain (postherpetic neuralgia), cranial nerve palsies, zoster paresis, meningoencephalitis, cerebellitis, myelopathy, multiple ocular disorders and vasculopathy that can mimic giant cell arteritis. All of the neurological and ocular disorders listed above may also develop without rash. Diagnosis of VZV-induced neurological disease may require examination of cerebrospinal fluid (CSF), serum and/ or ocular fluids. In the absence of rash in a patient with neurological disease potentially due to VZV, CSF should be examined for VZV DNA by PCR and for anti-VZV IgG and IgM. Detection of VZV IgG antibody in CSF is superior to detection of VZV DNA in CSF to diagnose vasculopathy, recurrent myelopathy, and brainstem encephalitis. Oral antiviral drugs speed healing of rash and shorten acute pain. Immunocompromised patients require intravenous acyclovir. First-line treatments for post-herpetic neuralgia include tricyclic antidepressants, gabapentin, pregabalin, and topical lidocaine patches. VZV vasculopathy, meningoencephalitis, and myelitis are all treated with intravenous acyclovir.