Neurology: neurosyphilis (tabes dorsalis): practice question

A General Medicine 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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General Medicine · Neurology: neurosyphilis (tabes dorsalis)

Sample item

A 55-year-old man has lightning pains in his legs, a wide-based gait that is worse in the dark, absent ankle jerks, a positive Romberg sign and small irregular pupils that accommodate but do not react to light. Serum treponemal tests are positive. What is the best next step?

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

The answer and the reasoning

D. Examine the cerebrospinal fluid, then give high-dose intravenous benzylpenicillin for 10 to 14 days

Lightning pains, sensory ataxia, areflexia and Argyll Robertson pupils indicate tabes dorsalis, a form of late neurosyphilis. CSF examination (cells, protein, VDRL) confirms CNS involvement, and treatment is aqueous benzylpenicillin 18 to 24 million units daily intravenously for 10 to 14 days to achieve treponemicidal CSF levels. Benzathine penicillin does not reach adequate CSF concentrations.

Option by option

  • A. Give oral doxycycline for 14 days without lumbar puncture

    Doxycycline is an alternative only in penicillin allergy and without CSF testing it is not the preferred approach.

  • B. Give a single intramuscular dose of benzathine penicillin

    A single benzathine dose is for early syphilis and does not give adequate CNS levels.

  • C. Give weekly intramuscular benzathine penicillin for three weeks without CSF testing

    The weekly benzathine regimen is for late latent syphilis without neurological involvement.

  • D. Examine the cerebrospinal fluid, then give high-dose intravenous benzylpenicillin for 10 to 14 days (correct)

    High-dose intravenous penicillin penetrates the CSF and is the standard therapy for neurosyphilis.

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 General Medicine question

What is the answer to this General Medicine question?

The best answer is D, Examine the cerebrospinal fluid, then give high-dose intravenous benzylpenicillin for 10 to 14 days. Lightning pains, sensory ataxia, areflexia and Argyll Robertson pupils indicate tabes dorsalis, a form of late neurosyphilis.

Why is "Give oral doxycycline for 14 days without lumbar puncture" not the answer?

Doxycycline is an alternative only in penicillin allergy and without CSF testing it is not the preferred approach.

Why is "Give a single intramuscular dose of benzathine penicillin" not the answer?

A single benzathine dose is for early syphilis and does not give adequate CNS levels.

Why is "Give weekly intramuscular benzathine penicillin for three weeks witho…" not the answer?

The weekly benzathine regimen is for late latent syphilis without neurological involvement.

What concept does this question test?

It tests Neurology: neurosyphilis (tabes dorsalis) in General Medicine. CSF examination (cells, protein, VDRL) confirms CNS involvement, and treatment is aqueous benzylpenicillin 18 to 24 million units daily intravenously for 10 to 14 days to achieve treponemicidal CSF levels. Benzathine penicillin does not reach adequate CSF concentrations.

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 Neurology: neurosyphilis (tabes dorsalis)?

For each disease know the classic presentation, the best test, and the first-line treatment. Then use the flashcards and the other General Medicine 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.