[Anti-VGKC Complex Antibodies and Limbic Encephalitis]

Anti-voltage-gated potassium channel (VGKC) antibodies are now understood to be antibodies against associated proteins leucine-rich glioma-inactivated 1 (LGI1) and contactin-associated protein-like 2 (CASPR2) and are detected using a cell-based assay. Anti-LGI1 or anti-CASPR2 antibody-positive patients present characteristics of limbic encephalitis, which is usually seen in middle-aged men and women who present with mainly amnesia and seizures. Faciobrachial dystonic seizures are seen specifically in LGI1 antibody-positive patients, and neuromyotonia is predominantly seen in CASPR2 antibody-positive patients. Both groups of patients greatly improve with immunotherapy; however, amnesia tends to last a long time and some patents experience a relapse. Some patients with limbic encephalitis present with only memory disturbance or seizures, and some are diagnosed with degenerative dementia or chronic epilepsy, suggesting the importance of early autoantibody testing for a diagnosis.