Prognostic Factors and Clinical Characteristics of Varicella Zoster Virus Meningitis: Impact of Treatment Delay and Age-Related Differences in a Japanese Tertiary Hospital

Objectives: Varicella zoster virus (VZV) meningitis is a complication of herpes zoster that causes high rates of residual symptoms. However, prognostic factors and optimal management strategies remain unclear. This study investigated factors affecting functional outcomes, age-related differences, and the impact of prior oral antiviral therapy in VZV meningitis. Methods: This retrospective observational study enrolled patients admitted for aseptic meningitis between 2013 and 2022. The primary outcome was residual symptoms at discharge, defined as a ≥1-point increase in the modified Rankin Scale (mRS) from baseline. Multiple logistic regression identified independent risk factors. Results: Among 176 patients with aseptic meningitis, 60 (34.1%) had VZV meningitis. Patients with VZV meningitis had higher rates of residual symptoms (43.3% vs. 12.9%, p < 0.001). Independent predictors of residual symptoms included delayed intravenous acyclovir initiation (odds ratio [OR] = 1.303, 95% confidence interval [CI] = 1.060–1.601, p = 0.012), corresponding to a 30.3% increase in the odds of residual symptoms for each additional day before treatment initiation, and pre-onset mRS (OR = 2.352, 95% CI = 1.056–5.237, p = 0.036). Patients ≥ 50 years old displayed lower rates of headache (75.0% vs. 96.9%, p = 0.020), neck stiffness (25.0% vs. 62.5%, p = 0.005), and CSF pleocytosis (56/μL vs. 142/μL, p = 0.023). Prior oral antiviral therapy was not associated with a rate of residual symptoms (p = 0.795). Conclusions: Delayed initiation of intravenous acyclovir was independently associated with residual symptoms at discharge, whereas older patients often presented with atypical clinical features, requiring heightened clinical suspicion. Given the lack of observed benefit associated with prior oral antiviral therapy, prompt initiation of intravenous acyclovir should be considered when VZV meningitis is suspected.