Neuropsychological and Functional Outcome after La Crosse Encephalitis in Marine Recruit: A Case Report and Literature Review

La Crosse virus is a rare infection in humans that can cause encephalopathy and neuroinvasive disease following infection. While pediatric outcomes have been studied, long-term neuropsychological and functional outcomes in adults remain undocumented. This case report compares existing literature with the extended clinical course of a 19-year-old, young adult male Marine recruit who contracted LACV. The Marine presented with lethargy, altered mental status, and abnormal neuroimaging. After improvements in alertness and command following, he was transferred from acute care to an inpatient neurorehabilitation unit. Disability was measured with the Functional Independence Measure (FIM). Cognitive impairment was documented with neuropsychological assessments. After rehabilitation discharge, he was readmitted approximately 4.75 years postinfection for a respite stay and re-evaluated. FIM scores at admission to the neurorehabilitation facility reflected nearly total dependence. He emerged from a confusional state by 3.5 months postinfection but with severe and nearly global cognitive impairment. By 4.75 years, he showed improved independence in self-care and mobility. Neuropsychological gains were observed in the domains of memory, attention, and executive functioning. Persistent deficits in processing speed and motor dexterity remained. This case highlights the potential for significant long-term functional and cognitive recovery following severe La Crosse encephalitis with global impairment acutely. Periodic neuropsychological re-evaluation may be warranted after infection to inform updated rehabilitation goals and maximize functional independence.