Falls related to faciobrachio-crural dystonic seizures in a case of leucine-rich glioma-inactivated 1 antibody-positive encephalitis

Faciobrachial dystonic seizures are pathognomonic for leucine-rich glioma-inactivated 1 (LGI1) antibody-positive encephalitis, and can present as a faciobrachio-crural dystonic seizure (FBCDS) phenotype when the lower extremities are involved. A 77-year-old woman was admitted to our hospital with a 3-week history of recurrent falls. Sudden unilateral knee buckling due to FBCDS while standing led to falls, resulting in multiple contusions on her face and extremities. Brain MRI showed no abnormalities. Serum testing revealed positive LGI1 antibodies, confirming the diagnosis of LGI1 antibody-positive encephalitis. The symptoms resolved completely following combined treatment with immunotherapy and antiseizure medications. Clinicians need to recognize FBCDS as a rare but critical differential diagnosis in patients with repeated falls. Prompt identification of FBCDS and early treatment are essential to prevent serious injuries and progression of encephalitis.