Spine: canal diameter in cervical myelopathy: practice question

A Orthopaedics 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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Orthopaedics · Spine: canal diameter in cervical myelopathy

Sample item

A lateral cervical radiograph shows an anteroposterior diameter of the cervical spinal canal of 11 mm. What is the significance?

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

The answer and the reasoning

B. Developmental canal stenosis increasing the risk of myelopathy

The normal sagittal canal diameter in the cervical spine is about 17 mm, and below about 13 mm the cord has little reserve, so even minor disc or osteophyte encroachment can cause myelopathy. A small developmental canal increases this risk. It is assessed on lateral radiographs or MRI.

Option by option

  • A. Evidence of a cervical rib

    A cervical rib is a bony anomaly causing thoracic outlet symptoms.

  • B. Developmental canal stenosis increasing the risk of myelopathy (correct)

    Correct. A diameter of 11 mm indicates a narrow canal with myelopathy risk.

  • C. A sign of ankylosing spondylitis

    Ankylosing spondylitis causes syndesmophytes and fusion.

  • D. A normal canal

    A normal canal measures roughly 17 mm.

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 Orthopaedics question

What is the answer to this Orthopaedics question?

The best answer is B, Developmental canal stenosis increasing the risk of myelopathy. The normal sagittal canal diameter in the cervical spine is about 17 mm, and below about 13 mm the cord has little reserve, so even minor disc or osteophyte encroachment can cause myelopathy.

Why is "Evidence of a cervical rib" not the answer?

A cervical rib is a bony anomaly causing thoracic outlet symptoms.

Why is "A sign of ankylosing spondylitis" not the answer?

Ankylosing spondylitis causes syndesmophytes and fusion.

Why is "A normal canal" not the answer?

A normal canal measures roughly 17 mm.

What concept does this question test?

It tests Spine: canal diameter in cervical myelopathy in Orthopaedics. A small developmental canal increases this risk. It is assessed on lateral radiographs or MRI.

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 Spine: canal diameter in cervical myelopathy?

Pair each fracture with its classic complication and nerve injured. Then use the flashcards and the other Orthopaedics 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.