Characteristics of meningitis/encephalitis in adult patients with varicella-zoster virus infection: Experience from tertiary centers in Saga prefecture, Japan

Objective: To clarify the characteristics of meningitis/encephalitis resulting from the varicella-zoster virus (VZV) in adult patients in Saga Prefecture, Japan, since the availability of amenamevir. Methods: We retrospectively examined the characteristics of consecutive adult patients diagnosed with VZV meningitis/encephalitis referred to five tertiary hospitals covering Saga Prefecture from September 2017 to August 2023. We also investigated the trend in using antiviral agents for herpes zoster treatment by using administrative claim data from the Japanese Medical Data Center (JMDC) database. Results: The Glasgow Outcome Scale (GOS) and modified Rankin Scale (mRS) at the peak phase were not significantly associated with the age of patients, whereas the mRS at 1 month and GOS and mRS scores at the last assessment tended to be worse as the age of onset increases (P < 0.01, 0.05, and 0.001, respectively), indicating poorer outcomes in elderly patients. The prescription rate of amenamevir for herpes zoster treatment in our patients was 57.1 % (8 of 14 cases), which was significantly higher than that of the JMDC database in Saga Prefecture alone (28.1 %, P < 0.05) and across Japan (25.8 %, P < 0.01). GOS and mRS at baseline, 1 month, and the last assessment were not significantly different between patients receiving amenamevir and those receiving other antiviral agents for herpes zoster treatment. Conclusion: Our study results suggested poorer outcomes in elderly patients and a high proportion of patients prescribed amenamevir. Lower the CSF transfer rate of amenamevir may increase the risk of developing meningitis/encephalitis in patients with herpes zoster.