The Expanding Spectrum of Herpesvirus Infections of the Nervous System

Herpesviruses cause various acute, subacute, and chronic disorders of the central (CNS) and peripheral (PNS) nervous systems in adults and children. Both immunocompetent and immunocompromised individuals may be affected. Zoster (shingles), a result of reactivation of varicella zoster virus (VZV), is the most frequent neurologic complication. Other neurological complications 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 are associated with Epstein Barr Virus (EBV); myelitis with VZV, CMV, EBV, and HSV-2; and ventriculitis/encephalitis with VZV and CMV. Brainstem encephalitis due to HSV and VZV, and polymyeloradiculitis due to CMV are well documented. HHV-6 produces childhood exanthem subitum (roseola) and febrile convulsions. Immunocompetent and immunocompromised hosts manifest different incidences and patterns of herpesvirus infections. For example, stroke due to VZV-mediated large vessel disease (herpes zoster ophthalmicus) occurs predominantly in immunocompetent hosts, while small vessel disease (leukoencephalitis) and ventriculitis develop almost exclusively in immunocompromised patients. EBV-associated primary CNS lymphomas also are restricted to immunosuppressed individuals. Recent large CSF PCR studies have shown that VZV, EBV, and CMV more frequently produce meningitis, encephalitis, or encephalopathy in immunocompetent hosts than was formerly realized. We review herpesvirus infections of the nervous system and illustrate the expanding spectrum of disease by including examples of a 75-year-old male on steroid treatment for chronic lung disease with fatal HSV-2 meningitis and an 81-year-old male with myasthenia gravis, long-term azathioprine use, and an EBV-associated primary CNS lymphoma.