Primary Varicella-Associated Meningoencephalitis with Cerebellar Features in a Vaccinated Adolescent: A Case Report

A bstract Varicella-zoster virus (VZV) is an uncommon cause of central nervous system (CNS) infection in immunocompetent children, particularly following primary varicella infection. This report describes a rare case of primary varicella-associated meningoencephalitis in a vaccinated, immunocompetent adolescent. A 14-year-old boy presented with gait instability, dysarthria, nystagmus, and drowsiness shortly after varicella infection. Cerebrospinal fluid (CSF) analysis showed lymphocytic pleocytosis with mildly elevated protein. CSF VZV polymerase chain reaction (PCR) was negative, but CSF VZV immunoglobulin G (IgG) was positive. Brain MRI revealed parietal leptomeningeal enhancement with brain edema. Treatment with intravenous acyclovir and dexamethasone resulted in complete neurological recovery. VZV should be considered in pediatric CNS infections following recent varicella, even when CSF PCR is negative. CSF VZV IgG, in conjunction with clinical and radiological findings, may support a probable diagnosis.