Mild Influenza-Associated Encephalitis with Predominant Neuropsychiatric Manifestations in a Child: A Case Report

Abstract

Influenza-associated encephalitis (IAE) is a rare but serious complication of influenza infection, predominantly affecting children. While most reported cases present with moderate to severe neurological symptoms, mild and self-limiting forms remain underrecognized. We report the case of a previously healthy 9-year- old boy who presented with fever, lethargy, behavioral changes, and two episodes of nocturnal complex behavior concerning for seizures during the course of an influenza-like illness. Laboratory evaluations were notable for leukopenia and elevated D-dimer levels. Neuroimaging revealed a medial right temporal arachnoid cyst, and cerebrospinal fluid (CSF) analysis showed mild pleocytosis with positive influenza A PCR. Electroencephalography was normal. The patient was managed with intravenous antibiotics, antiviral therapy, and supportive care. His symptoms resolved rapidly without neurological sequelae, and he made a complete recovery. This case highlights that influenza-associated encephalitis can present with mild, transient neuropsychiatric symptoms. It demonstrates that a positive respiratory influenza test does not preclude central nervous system involvement, underscoring the importance of cerebrospinal fluid analysis for diagnosis and to avoid unnecessary interventions