Neuropsychological course of voltage-gated potassium channel and glutamic acid decarboxylase antibody related limbic encephalitis

Background and purpose: Autoantibodies (abs) to glutamic acid decarboxylase (GAD) and to voltage-gated potassium channels (VGKC) induce distinct courses of limbic encephalitis, related to MRI findings, seizure outcome and cognition. Methods: A detailed analysis of the cognitive course of the two forms is presented, spanning a median time interval of 28 months, including parameters of attention, learning and memory in 15 VGKC-ab-positive and 16 GAD-ab-positive patients. Results: In both groups, the initially significantly impaired attention performance recovered to a putatively premorbid level. In VGKC patients the partially severely impaired learning and memory performance improved under treatment but remained subnormal at last follow-up. By contrast, GAD-ab-positive patients had initially less impaired learning and memory scores but did not show an improvement under treatment. Conclusions: The results provide evidence of distinct relations between inductive processes and cognitive outcome in VGKC-ab-positive and GAD-ab-positive sub-forms of limbic encephalitis, which possibly depend on differences in pathogenic molecular mechanisms and affected cerebral loci.