In this study, intracerebroventricular infusion of a CSF-derived anti-LGI1 autoantibody into rodent brains caused convulsive and non-convulsive seizures mimicking the epileptic phenotype in LGI1 encephalitis patients during the acute disease phase, as well as changes in behavior and acute brain MRI scans. Here, LGI1 is linked to viral encephalitis.