Question

For the AP axial projection of the skull, if the patient extends their neck, how would the dorsum sellae appear in the radiograph?

1) Superior to the foramen magnum
2) Superimposed over the arch of C1
3) Inferior to the petrous ridge
4) Foreshortened

Answer 1

In an AP axial projection of the skull, extending the neck displaces the dorsum sellae's projected position upward, making it appear superior to the foramen magnum.

Step-by-step explanation:

For the AP axial projection of the skull, if the patient extends their neck, the dorsum sellae will appear to be projected superior to the foramen magnum. This is because the extension of the neck would cause the base of the skull to tilt backward, changing the trajectory of the X-ray beam in relation to the dorsum sellae. Typically, correct positioning for an AP axial projection requires the central ray to be directed through the foramen magnum to properly visualize the dorsum sellae and increasing neck extension would displace the dorsum sellae's projected position upward relative to the foramen magnum on the radiograph.