Neuroanatomy: motor neuron disease: practice question

A Anatomy 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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Anatomy · Neuroanatomy: motor neuron disease

Sample item

A 55-year-old man has wasting and fasciculations of the small hand muscles together with spasticity and brisk reflexes in the legs. Sensation and sphincter function are normal. Which neurons are degenerating?

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

The answer and the reasoning

A. Corticospinal and anterior horn motor neurons

Amyotrophic lateral sclerosis combines upper motor neuron loss (spasticity, brisk reflexes) with lower motor neuron loss (wasting, fasciculations) and spares sensation and sphincters.

Option by option

  • A. Corticospinal and anterior horn motor neurons (correct)

    Correct. Degeneration of both upper and lower motor neurons explains the mixed picture with preserved sensation.

  • B. Anterior horn cells only

    Anterior horn loss alone, as in poliomyelitis, gives flaccid weakness without spasticity.

  • C. Purkinje cells and olivary neurons

    Purkinje and olivary loss causes cerebellar ataxia and does not explain wasting with spasticity.

  • D. Dorsal root ganglion sensory neurons

    Sensory neuron loss would produce numbness and ataxia, which are absent here.

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 Anatomy question

What is the answer to this Anatomy question?

The best answer is A, Corticospinal and anterior horn motor neurons. Amyotrophic lateral sclerosis combines upper motor neuron loss (spasticity, brisk reflexes) with lower motor neuron loss (wasting, fasciculations) and spares sensation and sphincters.

Why is "Anterior horn cells only" not the answer?

Anterior horn loss alone, as in poliomyelitis, gives flaccid weakness without spasticity.

Why is "Purkinje cells and olivary neurons" not the answer?

Purkinje and olivary loss causes cerebellar ataxia and does not explain wasting with spasticity.

Why is "Dorsal root ganglion sensory neurons" not the answer?

Sensory neuron loss would produce numbness and ataxia, which are absent here.

What concept does this question test?

It tests Neuroanatomy: motor neuron disease in Anatomy. The correct option holds because: Correct. Degeneration of both upper and lower motor neurons explains the mixed picture with preserved sensation.

How hard is this question?

We tag it as an application question: it asks you to use a fact on a patient or a finding. 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 Neuroanatomy: motor neuron disease?

Learn every nerve by its route, its muscles and what a lesion looks like at the bedside. That one habit answers a large share of questions. Then use the flashcards and the other Anatomy 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.