The goal of this observational study is to learn about the clinical characteristics, risk factors, and long-term outcomes of varicella zoster virus (VZV)-related central nervous system (CNS) infections in adults. The main questions it aims to answer are:

What are the risk factors associated with VZV meningitis and encephalitis? Which clinical and laboratory findings are associated with complications and poor functional outcomes? Researchers will collect retrospective data from participating centers across the country, including demographic, clinical, laboratory, imaging, and treatment variables. Participants diagnosed with VZV-related central nervous system infections will be followed through medical records, and outcomes such as complications, functional status, and mortality will be evaluated.

Varicella zoster virus (VZV) is a well-established cause of central nervous system infections, including meningitis and encephalitis, which may lead to significant morbidity and mortality. These infections can occur with or without the typical dermatomal rash and may present with a wide spectrum of neurological findings. With increasing life expectancy and the widespread use of immunosuppressive and immunomodulatory therapies, the incidence of VZV reactivation and related complications is expected to rise.

Despite advances in molecular diagnostic methods, which have improved the timely and accurate detection of VZV in cerebrospinal fluid, large-scale multicenter data on VZV-related central nervous system infections remain limited, particularly at the national level.

This multicenter retrospective cohort study aims to evaluate the clinical features, risk factors, and functional outcomes of adult patients diagnosed with VZV meningitis and encephalitis. Data will be collected from participating centers using a standardized dataset, including demographic characteristics, clinical presentation, comorbidities, laboratory findings, cerebrospinal fluid analysis, imaging results, treatment details, and follow-up outcomes.

The study will compare patients with and without complications to identify factors associated with adverse outcomes. Complications assessed during follow-up (minimum 1 month, up to 12 months) will include neurological sequelae such as epilepsy, cognitive impairment, cranial nerve deficits, and functional disability measured by the Modified Rankin Scale. Mortality and intensive care unit requirements will also be evaluated.

Statistical analyses will be performed to determine associations between clinical variables and outcomes. Categorical variables will be compared using chi-square or Fisher's exact tests, and continuous variables will be analyzed according to their distribution. Logistic regression models will be used to identify independent predictors of complications. A p-value of <0.05 will be considered statistically significant.

The study will be conducted under the coordination of the Association of Infectious Diseases and Clinical Microbiology Specialists (BUHASDER).

Inclusion Criteria:

Age ≥18 years Molecular confirmation of VZV (PCR-Polymerase Chain Reaction) in CSF fluid Diagnosis of meningitis or encephalitis

Exclusion Criteria:

Missing key clinical data Inadequate follow-up

Adult patients (≥18 years) diagnosed with varicella zoster virus (VZV)-related central nervous system infections, including meningitis and encephalitis, identified from participating centers. Patients are included based on molecular confirmation of VZV in cerebrospinal fluid and availability of clinical follow-up data.