Organic mental disorders: anti-LGI1 limbic encephalitis: practice question

A Psychiatry question in the style of the NEET PG paper. Answer it first, then read why the right option is right and why each of the others is wrong.

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Psychiatry · Organic mental disorders: anti-LGI1 limbic encephalitis

Sample item

A 62-year-old man has brief, frequent jerks of the face and arm for several weeks, followed by memory loss and confusion. Serum sodium is 124 mmol/L. Which antibody is most likely?

Original practice item, not a recalled exam question. Nothing here is recorded.

The answer and the reasoning

C. Anti-LGI1 antibody

Anti-LGI1 encephalitis presents in older men with faciobrachial dystonic seizures, amnesia and confusion, and hyponatraemia is common. It responds to immunotherapy, and recognising the early seizures can prevent progression to cognitive decline.

Option by option

  • A. Anti-thyroid peroxidase antibody

    Anti-TPO antibodies occur in Hashimoto encephalopathy, which does not cause this seizure pattern.

  • B. Anti-NMDA receptor antibody

    Anti-NMDA receptor encephalitis typically affects young women with psychosis and dyskinesias.

  • C. Anti-LGI1 antibody (correct)

    Correct. Faciobrachial seizures, amnesia and hyponatraemia fit anti-LGI1 encephalitis.

  • D. Anti-Hu antibody

    Anti-Hu antibodies are linked with small-cell lung cancer and sensory neuronopathy.

Source note: Original NextPrep sample item — pending expert review. This item is original practice material awaiting independent expert review, so confirm important facts in a standard textbook.

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Questions about this Psychiatry question

What is the answer to this Psychiatry question?

The best answer is C, Anti-LGI1 antibody. Anti-LGI1 encephalitis presents in older men with faciobrachial dystonic seizures, amnesia and confusion, and hyponatraemia is common.

Why is "Anti-thyroid peroxidase antibody" not the answer?

Anti-TPO antibodies occur in Hashimoto encephalopathy, which does not cause this seizure pattern.

Why is "Anti-NMDA receptor antibody" not the answer?

Anti-NMDA receptor encephalitis typically affects young women with psychosis and dyskinesias.

Why is "Anti-Hu antibody" not the answer?

Anti-Hu antibodies are linked with small-cell lung cancer and sensory neuronopathy.

What concept does this question test?

It tests Organic mental disorders: anti-LGI1 limbic encephalitis in Psychiatry. It responds to immunotherapy, and recognising the early seizures can prevent progression to cognitive decline.

How hard is this question?

We tag it as a multi-step question: it asks you to combine more than one idea. The tag is our own editorial judgement, not an official difficulty rating, so read the reason for every option, not only the answer.

How should I study Organic mental disorders: anti-LGI1 limbic encephalitis?

Learn each diagnosis by its core features and its first-line treatment. Then use the flashcards and the other Psychiatry questions on this site to test what stuck.

Is this a real NEET PG question?

No. It is an original practice item (editorial status: sample, version 1). NextPrep does not publish recalled or leaked questions, and independent faculty review of this item has not been completed yet, so confirm important facts in a standard textbook.