A Case of Anti-Leucine-Rich Glioma-Inactivated Protein 1 (Anti-LGI1) Limbic Encephalitis With Normal Imaging.

Anti-leucine-rich glioma-inactivated 1 limbic encephalitis (anti-LGI1 LE) is a rare autoimmune limbic encephalitis with a potentially misleading presentation that can delay diagnosis and treatment. The incremental progression of widely variable symptoms with a prominent behavioral disturbance can conceal the disease and prompt an initial psychiatric diagnosis. Although specific MRI findings ought to be evident by the time the disease progresses to frank limbic encephalitis, it appears inconsistent and ill-defined and is thus unreliable. Nevertheless, brain imaging remains prominent in the discussion, even included in some guidelines for diagnosing anti-LGI1 LE. Here, we present a case of a patient who presented after a suicide attempt with a long history of psychiatric issues, aberrant "spasms," and subsequently encephalopathy, who was eventually diagnosed with anti-LGI1 LE only after delayed CSF antibodies studies. In this patient, symptoms emerged over two years, with multiple brain MRIs being negative, including the one completed during the hospital admission in focus. The purpose of this case report is to encourage maintaining a broad differential when patients present with bizarre symptoms. This report underlies the importance of thorough clinical evaluation, utilization of multiple diagnostic resources, and the need for heightened awareness among healthcare providers about the subtleties of autoimmune encephalitis presentations. With anti-LGI1 LE already being severely underdiagnosed, it is important to continue reviewing various cases of patients who are diagnosed with anti-LGI1 LE and further review to understand its pathophysiology and common clinical presentation. This case also underscores the ongoing evolution in understanding anti-LGI1 LE and highlights that patients may present with unfamiliar symptoms or diagnostic challenges. The overall objective is to help providers recognize anti-LGI1 LE earlier, so treatment can be initiated sooner, leading to a better prognosis for patients.