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LGI1 autoimmune limbic encephalitis — ABIM Board MCQ

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HardNeurologyLGI1 autoimmune limbic encephalitisABIM Board

A 58-year-old man has subacute memory loss, hyponatremia, medial-temporal MRI signal, and dozens of brief faciobrachial dystonic seizures daily. CSF HSV PCR is negative, and serum and CSF testing confirms LGI1 antibodies. Levetiracetam has not reduced the events. What is the most appropriate disease-directed step?

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Correct answer: C — Start immunotherapy and continue antiseizure treatment during early recovery

The best answer is “Start immunotherapy and continue antiseizure treatment during early recovery”. Faciobrachial dystonic seizures are characteristic of LGI1 encephalitis and often respond poorly to antiseizure drugs alone. Prompt corticosteroid-based immunotherapy, with IVIG or plasma exchange selected by severity and patient factors, treats the underlying inflammation and may prevent further cognitive decline. Sodium correction and antiseizure medication are supportive but do not replace immune treatment.

Reference: Best-Practice Recommendations for Autoimmune Encephalitis: https://pmc.ncbi.nlm.nih.gov/articles/PMC8292591/