Patients with
viral infections of the central nervous system (CNS) may present with a variety of neurological symptoms, most commonly dominated by either
encephalitis or
meningitis. The aetiological panorama varies in different parts of the world as well as over time. Thus, virological first-line diagnostics must be adapted to the current epidemiological situation and to the individual patient history, including recent travels. This review focuses on the diagnostics and treatment of
viral CNS infections in the immunocompetent host from a Northern European perspective. Effective
vaccines are available for viruses such as poliovirus and tick-borne encephalitis virus (TBEV) and for the childhood diseases morbilli (
measles),
rubella (
German measles),
parotitis (
mumps) and
varicella (
chickenpox). However, cases do appear due to suboptimal immunization rates. In
viral CNS infections, epidemiological surveillance is essential for establishing preventive strategies and for detecting emerging viruses. Knowledge of the possibilities and limitations of diagnostic methods for specific
viral CNS infections is vital. A positive cerebral spinal fluid (CSF) polymerase chain reaction (PCR) finding is usually reliable for aetiological diagnosis. The demonstration of intrathecal antibody synthesis is useful for confirming the aetiology in a later stage of disease, hitherto sufficiently evaluated in
herpes simplex encephalitis (HSE) and
tick-borne encephalitis (TBE). Despite improved virological and differential diagnostic methods, aetiology remains unknown in about half of the cases with suspected
viral encephalitis.
Antiviral treatment is available chiefly for
infections caused by herpesviruses, and
acyclovir (
aciclovir) is the
drug of choice for empirical
therapy in suspected
viral encephalitis. However, randomized, controlled
antiviral trials have only been conducted for HSE, while such studies are lacking in other
viral CNS infections. Viral cytolysis and immune-mediated mechanisms may contribute to varying extents to neurological damage. Although the brain damage is believed to depend, to a varying degree, on the intrathecal host immune response, the use of
corticosteroids in
viral CNS infections is scarcely studied, as is specific treatment for
neuroinflammation. Improved
antiviral and immunomodulating treatment is desirable. Since neurological sequelae are still abundant, follow-up after severe viral
CNS disease must include a neuropsychological assessment and an individually adapted rehabilitation plan.