Summary Objective Seizures develop in 80% of patients with anti– N ‐methyl‐ d ‐aspartate receptor (NMDAR) encephalitis, and these represent a major cause of morbidity and mortality. Anti‐NMDAR antibodies have been linked to memory loss in encephalitis; however, their role in seizures has not been established. We determined whether anti‐NMDAR antibodies from autoimmune encephalitis patients are pathogenic for seizures. Methods We performed continuous intracerebroventricular infusion of cerebrospinal fluid (CSF) or purified immunoglobulin (IgG) from the CSF of patients with anti‐NMDAR encephalitis or polyclonal rabbit anti‐NMDAR IgG, in male C57BL/6 mice. Seizure status during a 2‐week treatment was assessed with video‐electroencephalography. We assessed memory, anxiety‐related behavior, and motor function at the end of treatment and assessed the extent of neuronal damage and gliosis in the CA1 region of hippocampus. We also performed whole‐cell patch recordings from the CA1 pyramidal neurons in hippocampal slices of mice with seizures. Results Prolonged exposure to rabbit anti‐NMDAR IgG, patient CSF, or human IgG purified from the CSF of patients with encephalitis induced seizures in 33 of 36 mice. The median number of seizures recorded in 2 weeks was 13, 39, and 35 per mouse in these groups, respectively. We observed only 18 brief nonconvulsive seizures in 11 of 29 control mice (median seizure count of 0) infused with vehicle (n = 4), normal CSF obtained from patients with noninflammatory central nervous system (CNS) conditions (n = 12), polyclonal rabbit IgG (n = 7), albumin (n = 3), and normal human IgG (n = 3). We did not observe memory deficits, anxiety‐related behavior, or motor impairment measured at 2 weeks in animals treated with CSF from affected patients or rabbit IgG. Furthermore, there was no evidence of hippocampal cell loss or astrocyte proliferation in the same mice. Significance Our findings indicate that autoantibodies can induce seizures in anti‐NMDAR encephalitis and offer a model for testing novel therapies for refractory autoimmune seizures.
Antibody Prevalence in Epilepsy and Encephalopathy score: Increased specificity and applicability
Objective: To evaluate the impact of age on recovery from multiple sclerosis relapses. Background: Increasing disability in multiple sclerosis is a consequence of progressive disease and incomplete relapse recovery. Methods: The first and last-ever relapse data (357 relapses in 193 patients) from the Olmsted County population-based multiple sclerosis cohort were systematically reviewed for age, fulminance, location (optic nerve, brainstem/cerebellar, spinal cord), peak deficit, and maximum recovery. Three different relapse-outcome measures were studied both as paired analyses and as an overall group effect: change from peak deficit to maximum recovery in raw functional system score related to the relapse (ΔFSS), a previously published FSS-based relapse-impact model, and change from peak deficit to maximum recovery in Extended Disability Status Scale (ΔEDSS) score. Results: Older age was linearly associated with worse recovery in the ΔFSS outcome ( p = 0.002), ΔEDSS outcome ( p < 0.001), and the FSS-based relapse-impact model ( p < 0.001). A multivariate analysis of ΔFSS outcome linked poor recovery to older age ( p = 0.015), relapse location (transverse myelitis or brainstem/cerebellar syndrome; p < 0.001), and relapse fulminance ( p = 0.004). Conclusion: Multiple sclerosis-relapse recovery declines in a linear fashion with increased age, which should be considered when making treatment decisions.