Paraneoplastic syndromes and autoimmune encephalitis: Five new things.

We review novel findings in paraneoplastic syndromes including the Lambert-Eaton myasthenic syndrome, and then focus on the novel disorders associated with antibodies against cell surface antigens, discussing the importance and caveats of antibody testing, and providing an algorithm for interpretation of results. In anti-NMDAR encephalitis 2 novel findings include the recognition of a characteristic EEG pattern ("extreme delta brush") in 30% of patients and the demonstration of a fronto-temporo-occipital gradient of glucose metabolism that correlates with disease activity. In limbic encephalitis, antibodies to GABA(B) receptor are the most frequently detected in patients with small-cell lung cancer who are anti-Hu negative, and antibodies to mGluR5 distinctively associate with Hodgkin lymphoma (Ophelia syndrome). We also address the syndromes associated with "VGKC-complex antibodies," a problematic term that groups well-characterized immune-mediated disorders (LGI1, Caspr2) with others that lack syndrome specificity, are less responsive to treatment, and for which the target antigens are unknown.