The expanding spectrum of herpesvirus infections of the nervous system

Herpesviruses cause various acute, subacute, and chronic disorders of the c entral (CNS) and peripheral (PNS) nervous systems in adults and children. B oth immunocompetent and immunocompromised individuals may be affected. Zost er (shingles), a result of reactivation of varicella zoster virus (VZV), is the most frequent neurologic complication. Other neurological complication s include encephalitis produced by type I herpes simplex virus (HSV-1), and less frequently HSV-2, as well as by VZV and cytomegalovirus (CMV). Acute meningitis is seen with VZV and HSV-2, and benign recurrent meningitis with HSV-2. Combinations of meningitis/ encephalitis and myelitis/radiculitis a re associated with Epstein Barr Virus (EBV); myelitis with VZV, CMV, EBV, a nd HSV-2; and ventriculitis/encephalitis with VZV and CMV. Brainstem enceph alitis due to HSV and VZV, and polymyeloradiculitis due to CMV are well doc umented. HHV-6 produces childhood exanthem subitum (roseola) and febrile co nvulsions. Immunocompetent and immunocompromised hosts manifest different i ncidences and patterns of herpesvirus infections. For example, stroke due t o VZV-mediated large vessel disease (herpes zoster ophthalmicus) occurs pre dominantly in immunocompetent hosts, while small vessel disease (leukoencep halitis) and ventriculitis develop almost exclusively in immunocompromised patients. EBV-associated primary CNS lymphomas also are restricted to immun osuppressed individuals. Recent large CSF PCR studies have shown that VZV, EBV, and CMV more frequently produce meningitis, encephalitis, or encephalo pathy in immunocompetent hosts than was formerly realized. We review herpes virus infections of the nervous system and illustrate the expanding spectru m of disease by including examples of a 75-year-old male on steroid treatme nt for chronic lung disease with fatal HSV-2 meningitis and an 81-year-old male with myasthenia gravis, longterm azathioprine use, and an EBV-associat ed primary CNS lymphoma.