The patterns of varicella zoster virus encephalitis.

Varicella zoster virus (VZV) encephalitis has become increasingly prevalent in the era of acquired immunodeficiency syndrome (AIDS), and a widening spectrum of pathological lesions has defined the disease in these and other severely immunosuppressed patients. VZV produces three distinct morphological patterns of brain damage. VZV can cause bland or hemorrhagic infarctions secondary to a large or medium vessel vasculopathy. Deep white matter, ovoid mixed necrotic, and demyelinative lesions occur as a consequence of small vessel vasculopathy, with demyelination dependent on the degree of additional oligodendrocyte infection. Distinctive Cowdry A intra-nuclear viral inclusions are rare in either large or small blood vessels or near infarctions, but are commonly found in glial cells at the edge of the smaller ovoid, demyelinative lesions. Ependymal and periventricular necrosis occurs as a result of vasculopathy of subependymal vessels and secondary infection of ependymal and other glial cells in the periventricular region. To clarify these patterns of VZV encephalitis and shed light on their pathogenesis, the authors have examined all cases of VZV encephalitis seen at our institution since 1984. Additionally, the authors review the extensive literature in an attempt to classify the patterns of VZV encephalitis into (1) large/ medium vessel vasculopathy with bland or hemorrhagic infarctions, (2) small vessel vasculopathy with mixed ischemic/demyelinative lesions, and (3) ventriculitis/periventriculitis. Although one of these three patterns often predominates clinically and radiographically, careful histological examination at autopsy shows mixed features in many cases.

Another case of virologically confirmed zoster sine herpete, with electrophysiologic correlation.

A third virologically-confirmed case of thoracic-distribution zoster sine herpete is reported. Electromyography (EMG) of paraspinal muscles demonstrated frequent fibrillation potentials restricted to chronically painful thoracic root segments. Treatment with intravenous acyclovir and oral famciclovir were ineffective. These findings suggest the usefulness of EMG of muscles corresponding to painful dermatomes, combined with virologic studies, to support the diagnosis of zoster sine herpete.

The vasculopathy of varicella-zoster virus encephalitis.

Varicella-zoster virus (VZV) encephalitis has become more prevalent in the era of acquired immunodeficiency syndrome and other immunosuppressive diseases and poses diagnostic and therapeutic challenges for clinicians, radiologists, and pathologists. Six cases studied at our institutions shed light on the patterns and pathogenesis of the disease. VZV encephalitis is predominantly a vasculopathy, involving small and large vessels, that generates seizures, mental changes, and focal deficits. Brain imaging reveals large and small ischemic or hemorrhagic infarcts, often both, of cortex and subcortical gray and white matter. Deep-seated white matter lesions often predominate and are ischemic and/or demyelinative, depending on the size of blood vessels involved and the amount of additional demyelination caused by infection of oligodendrocytes. The demyelinative lesions are smaller and less coalescent than those seen in progressive multifocal leukoencephalopathy.