Neuroanatomy: spinal shock: 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.

Try it

Anatomy · Neuroanatomy: spinal shock

Sample item

A man with an acute complete T6 cord transection has flaccid paralysis, absent reflexes and loss of tone below the level for several days. What mainly explains this early flaccidity?

ADeath of the anterior horn cells below the transectionBInterruption of the peripheral motor nerves at the level of injuryCExcessive inhibitory drive from the intact dorsal columnsDAbrupt withdrawal of tonic descending excitation to spinal motor neurons

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

The answer and the reasoning

D. Abrupt withdrawal of tonic descending excitation to spinal motor neurons

Spinal motor neurons below a lesion lose the continuous facilitation they receive from descending tracts and become temporarily hypo-excitable. As spinal circuits recover, hyperreflexia and spasticity replace the flaccid areflexic phase.

Option by option

A. Death of the anterior horn cells below the transection
Anterior horn cells below the lesion are intact and recover excitability.
B. Interruption of the peripheral motor nerves at the level of injury
A segmental level injury of nerves would cause only focal lower motor neuron signs.
C. Excessive inhibitory drive from the intact dorsal columns
The dorsal columns are ascending sensory pathways and do not drive motor inhibition.
D. Abrupt withdrawal of tonic descending excitation to spinal motor neurons (correct)
Correct. Loss of tonic descending facilitation produces temporary areflexia, called spinal shock.

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.

Questions about this Anatomy question

What is the answer to this Anatomy question?

The best answer is D, Abrupt withdrawal of tonic descending excitation to spinal motor neurons. Spinal motor neurons below a lesion lose the continuous facilitation they receive from descending tracts and become temporarily hypo-excitable.

Why is "Death of the anterior horn cells below the transection" not the answer?

Anterior horn cells below the lesion are intact and recover excitability.

Why is "Interruption of the peripheral motor nerves at the level of injury" not the answer?

A segmental level injury of nerves would cause only focal lower motor neuron signs.

Why is "Excessive inhibitory drive from the intact dorsal columns" not the answer?

The dorsal columns are ascending sensory pathways and do not drive motor inhibition.

What concept does this question test?

It tests Neuroanatomy: spinal shock in Anatomy. As spinal circuits recover, hyperreflexia and spasticity replace the flaccid areflexic phase.

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: spinal shock?

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.