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Neuroleptic malignant syndrome — USMLE Step 2 CK MCQ

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HardPsychiatryNeuroleptic malignant syndromeUSMLE Step 2 CK

A 66-year-old develops dozens of daily, one-second contractions of the right face and arm. Sodium is 126 mEq/L; MRI and routine EEG are initially normal. Serum testing detects LGI1 antibodies. Which treatment best prevents progression to cognitive limbic encephalitis?

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Correct answer: C — Begin early immunotherapy with high-dose glucocorticoids

Very brief, frequent unilateral face-and-arm contractions are faciobrachial dystonic seizures, a characteristic early manifestation of LGI1 autoimmunity. They can precede disabling memory loss and often respond poorly to antiseizure medication alone. Early immunotherapy—commonly high-dose glucocorticoids, with escalation individualized—rapidly reduces seizure burden and is associated with less progression to cognitive limbic encephalitis. Hyponatremia supports the syndrome but correction alone is not disease-modifying; normal routine EEG or MRI does not justify delay.

Reference: Brain: importance of early immunotherapy in faciobrachial dystonic seizures (PubMed). https://pubmed.ncbi.nlm.nih.gov/29272336/