HHV-6-induced hydrocephalus with ventricular septa formation in an immunocompetent adult: illustrative case.

BACKGROUND: Human herpesvirus 6 (HHV-6) is a neurotropic virus known to induce encephalitis in immunocompromised patients as well as a subset of pediatric patients. However, ventriculitis secondary to HHV-6 is a rare occurrence among immunocompetent adults. Although acquired hydrocephalus has been described to infrequently co-occur with HHV-6 encephalitis in pediatric and immunocompromised adult patients, it has not been described in an immunocompetent adult. OBSERVATIONS: The authors present a rare case of HHV-6 encephalitis and obstructive hydrocephalus in an immunocompetent adult patient. Despite CSF diversion, the emergence and proliferation of multiple septations throughout the ventricular system resulted in the progression of severe hydrocephalus. LESSONS: Previous studies have linked HHV-6 to inflammatory states, occurring predominantly among children and immunocompromised adults, that manifest primarily as meningitis and encephalitis. This case highlights the fact that HHV-6 can cause life-threatening ventriculitis and hydrocephalus in immunocompetent adults. Pathophysiological mechanisms of virus-induced neuroinflammation yielding intraventricular septation formation are reviewed. https://thejns.org/doi/10.3171/CASE25273.