Diagnostic Imaging - Spine

Question 1

What must be assessed before evaluating radiographs of the spine?

Answer 1

Positioning / centring.
- means GA in most cases.
- positioning aids necessary to ensure straight spine to image.
– legs reasonable parallel.
Exposure of the image and its quality.

Question 2

Important principle in radiographing spine.

Answer 2

Radiograph spine in several small chunks.
- to ensure primary beam passes straight through disc spaces.
– most accurate image of these is in centre of radiograph.
- if one long film produced, joint spaces cannot be assessed on outer edges of film.

Question 3

How to assess for rotation of the patient on spinal radiograph?

Answer 3

Look at ribs on thoracic region.
- should superimpose.
Look at transverse processes in cervical and lumbar regions.
- should superimpose.

Question 4

Evaluating the spine on radiograph - alignment and number of vertebrae.

Answer 4

• correct number of vertebrae in each anatomical region?
• Look for ventral margin of the vertebral canal.
• changes in alignment may be more subtle and may be more obvious on one projection than the other.

Question 5

Evaluation of spine on radiograph - individual vertebrae.

Answer 5

Shape of each vertebrae.
Margination - any proliferation or destruction?
Trabecular structure and overall opacity.
- compare w/ adjacent vertebrae.

Question 6

Evaluating the spine on radiography.
- Intervertebral disc spaces.

Answer 6

Width and opacity.
Mineralisation increases opacity.
Can only truly assess width on centre of radiograph image, not on periphery due to x ray beam divergence obliquely through disc spaces.
Look for increased opacity OUTSIDE of normal areas on superimposition.
Normal intervertebral foramen is radiolucent and the shape is analogous to a horse head.
- increased opacity in this area could indicate mineralised disc partially extruded into vertebral canal. – likely compressing effect.

Question 7

Myelography.
How does it work?

Answer 7

Only now really performed in conjunction w/ CT where MRI is not available.
Surrounds spinal cord and delineates subarachnoid space (between the dura and spinal cord, where CSF usually runs).
Localises lesions of spina cord.
- medullary lesions.
- lesions compressing cord.
– intra-dural or extra-dural.
Non-ionic water-soluble contrast medium.
- e.g. Omnipaque, Niopam.
- ionic cause seizures / arachnoiditis.

Question 8

1. Myelography indications.
2. What supersedes myelography?

Answer 8

1. Neuro dysfunction.
   Spinal pain.
   To further define lesions suspected on plain radiograph.
   - e.g. disc calcification/narrowing.
2. MRI where available.
   - CT may be adequate if mineralised disc material or bone lesion present.
   - CT myelography can be performed if MRI not available.

Question 9

Myelography complications.

Answer 9

Spinal cord damage (intramedullary injections).
Haemorrhage into cord.
Infection (meningitis).
Seizures - meningeal irritation by contrast medium or injection procedure itself.
Worsening of existing neuro signs.

Question 10

Most common lesion found with myelography.

Answer 10

Extra-dural.
- disc extrusion / protrusion.
Intra-medullary (anything that causes the cord to swell).
- e.g. cord oedema, myelitis, neoplasia.
Intradural/extra-medullary.
- e.g. nerve root tumour, meningioma.
– lesion is causing expansion of the space the CSF moves through.