Management strategies for herpesvirus infections of the CNS - Immunocompetent and immunocompromised patients

The known human herpesviruses (HHVs) include herpes simplex viruses type 1 and 2, varicella-zoster virus, cytomegalovirus, Epstein-Barr virus, and HHVs 6, 7 and 8, Almost all of them may induce CNS diseases, which can vary from mild to life threatening and are significantly different in immunocompetent and immunocompromised patients. An aetiological diagnosis is essential for optimal disease management, and the recently developed molecular diagnostic techniques have provided a rapid and sensitive means for herpesvirus identification. Effective antiherpesvirus agents have long been available, but the only regimen that can be recommended on the basis of proven efficacy in controlled trials is aciclovir (acyclovir) for herpes simplex encephalitis (HSE). Nevertheless, antiviral agents are empirically used in the treatment of various herpes-induced CNS complications and a number of examples of their efficacy have been reported. Most frequently, CNS disease results from direct virus-induced cytotoxicity. However, immune-mediated mechanisms may be involved in some cases, and cortisosteroids are also empirically employed. Despite the diagnostic advances and broader availability of antiviral compounds, the management of herpes-induced CNS complications is still difficult. A significant number of patients with HSE die, fail to regain normal function or relapse despite an initial therapeutic response. The current antiviral approaches are often unsatisfactory in immunocompromised patients and no optimal treatment has yet been established for the majority of herpes diseases of the CNS. Information regarding new treatment strategies, including different aciclovir regimens and the use of newer compounds or drug combinations, is needed and can only be provided by large multicentre studies.