Neuroimaging: Canavan disease: practice question

A Radiology 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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Radiology · Neuroimaging: Canavan disease

Sample item

An infant with macrocephaly and hypotonia has diffuse symmetrical subcortical white matter T2 hyperintensity including the U-fibres and thalami. MR spectroscopy shows markedly elevated N-acetylaspartate. What is the diagnosis?

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

The answer and the reasoning

D. Canavan disease

Aspartoacylase deficiency causes N-acetylaspartate to accumulate, with spongiform white matter disease and macrocephaly. Elevated NAA is unique to Canavan disease, whereas NAA is reduced in most other leukodystrophies.

Option by option

  • A. X-linked adrenoleukodystrophy

    Adrenoleukodystrophy typically starts in the parieto-occipital white matter in boys.

  • B. Alexander disease

    Alexander disease also causes macrocephaly, but with frontal predominance, a periventricular rim and normal or low NAA.

  • C. Metachromatic leukodystrophy

    Metachromatic leukodystrophy shows periventricular white matter change with a tigroid pattern and sparing of U-fibres.

  • D. Canavan disease (correct)

    Correct. Macrocephaly with a very high NAA peak is diagnostic of Canavan disease.

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 Radiology question

What is the answer to this Radiology question?

The best answer is D, Canavan disease. Aspartoacylase deficiency causes N-acetylaspartate to accumulate, with spongiform white matter disease and macrocephaly.

Why is "X-linked adrenoleukodystrophy" not the answer?

Adrenoleukodystrophy typically starts in the parieto-occipital white matter in boys.

Why is "Alexander disease" not the answer?

Alexander disease also causes macrocephaly, but with frontal predominance, a periventricular rim and normal or low NAA.

Why is "Metachromatic leukodystrophy" not the answer?

Metachromatic leukodystrophy shows periventricular white matter change with a tigroid pattern and sparing of U-fibres.

What concept does this question test?

It tests Neuroimaging: Canavan disease in Radiology. Elevated NAA is unique to Canavan disease, whereas NAA is reduced in most other leukodystrophies.

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 Neuroimaging: Canavan disease?

Learn signs with the image, and the disease they point to. Then use the flashcards and the other Radiology 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.