Rapidly Progressive Dementia With Recurrent Seizures and Hyponatremia; A Case of LGI1 Limbic Encephalitis

Objective N/A.

Background Leucine-Rich Glioma Inactivated Protein-1 (LGI1) autoimmune encephalitis was first described in 2001 as one of the syndromes caused antibodies against the voltage-gated potassium channels (VGKC) until it was discovered in 2010 that antibodies were instead being directed towards the protein LGI1. This often presents in males in their 60's and is often associated with faciobrachial dystonic seizures, which have become path pneumonic for this disease process.

Design/Methods N/A.

Results 77-year-old female with history of hyponatremia, anxiety, hypertension, and lacunar infarct presented for a concern for seizures. She presented for multiple episodes of reported generalized tonic seizures and was eventually found to have right frontotemporal seizures with impaired awareness. Magnetic Resonance Imaging (MRI) was repeated multiple times but were significantly degraded due to motion artifact and read as limited. Further discussion with husband was concerning for memory loss over the past 4 months, but patients children disputed this with several years of memory loss. After neuropsychological testing which demonstrated significant decline across multiple domains. MRI was revisited which was concerning for bilateral mesial temporal hyperintensities on Fluid-Attenuated Inversion Recovery (FLAIR). Patient underwent lumbar puncture given unremarkable workup thus far. CSF and serum both demonstrated LGI1 autoantibodies for which the patient received a 5 days course of IV methylprednisolone, IV immunoglobulins, and was eventually transitioned to rituximab with complete recovery of long term memory.

Conclusions This case demonstrates the complexity of evaluating a patient for reported rapidly progressive dementia and some of the pitfalls involved in the workup. This case demonstrates that when the initial workup is unremarkable, the patient should be evaluated for uncommon causes, such as autoimmune encephalitis. We diagnosed an atypical presentation of autoimmune encephalitis and documented the initial treatment and response to both first line and second line treatment with future plans to titrate the anti-epileptic drugs.