skip to main content

LGI1 Limbic Encephalitis — RACP Adult Medicine MCQ

Instant feedback + full explanation. One question, done properly.

HardNeurologyLGI1 Limbic EncephalitisRACP Adult Medicine

A 65-year-old man presents with faciobrachial dystonic seizures (brief, frequent, stereotyped jerks of face and arm), progressive cognitive decline, and severe hyponatraemia (Na⁺ 118 mmol/L). MRI shows bilateral mesial temporal T2/FLAIR hyperintensity. CSF anti-LGI1 antibodies are positive. What is the most likely diagnosis?

Educational content. Not a substitute for clinical judgement or local policy.

Reveal the answer and explanation

Correct answer: C — Limbic encephalitis (LGI1)

Faciobrachial dystonic seizures (pathognomonic for LGI1 encephalitis), cognitive decline, severe hyponatraemia (SIADH-like), and mesial temporal MRI changes with positive anti-LGI1 antibodies is LGI1 limbic encephalitis. It is rarely paraneoplastic (<10%). Treatment is immunotherapy (corticosteroids, IVIG, PLEX). FBDS respond poorly to antiepileptics but well to immunotherapy.

Reference: Graus 2016 Autoimmune Encephalitis Criteria; eTG Neurology 2024