LGI1 is a leucine-rich extracellular protein that functions as a critical regulator of neuronal excitability and synaptic transmission. Structurally, LGI1 acts as a ligand for ADAM22 and regulates voltage-gated potassium channels (VGKC) assembled from KCNA1, KCNA4, and KCNAB1 subunits by slowing channel inactivation [UniProt]. Additionally, LGI1 positively regulates AMPA-type glutamate receptor-mediated synaptic transmission and plays a role in synaptic assembly and neuronal development. Clinically, LGI1 is central to autoimmune encephalitis pathogenesis. Anti-LGI1 antibodies are among the most common causes of autoimmune encephalitis in developed countries 1, presenting as a characteristic syndrome of faciobrachial dystonic seizures (FBDS) and limbic encephalitis with cognitive impairment 2. LGI1 IgG4 antibodies disrupt LGI1's interaction with cognate proteins and alter AMPAR-mediated signaling, causing neuronal dysfunction 3. Anti-LGI1 encephalitis shows excellent immunotherapy responsiveness, particularly to corticosteroids, with 80% of patients showing substantial improvement 24. However, long-term sequelae including persistent amnesia and short-term memory deficits occur in approximately one-third of surviving patients 4. Early recognition of FBDS and characteristic MRI findings of temporal lobe hyperintensities without diffusion restriction are essential for prompt treatment initiation 5.