9.04: Zone C2 – Superior Mid-Pupillary Region
YOUR ASSIGNMENT FOR THIS LESSON
✅ Step #1: Review all content below.
✅ Step #2: Image the C2 zone on your own with your ultrasond, and using the checklist provided on this page, check off all key structures to be identified in this location.
TRANSDUCER POSITION AT C2
STANDARD C2 ORIENTATION:
TRANSVERSE & LONGITUDINAL
The intersection of the vertical line from mid-pupil to the horizontal line from the superior alar groove is the location of C2.
- First identify the periosteum. Then glide to a portion where the periosteal line is discontinuous. This is the infraorbital foramen.
- You can confirm this by turning on doppler and identifying arterial flow above the foramen.
- A hypoechoic region just above the foramen will correspond with the LLS / LAO muscles. Differentiating these muscles apart can be very challenging under ultrasound.
- If you have difficulty identifying the foramen, angulate the probe in the superior direction. The foramen is slightly angulated inferiorly and by angulating your probe you will visualize it more optimally.
EXAMPLE OF TRANSVERSE IMAGE ACQUIRED AT C2
ANATOMICAL LEGEND FOR C2 LOCATION IN TRANSVERSE
EXAMPLE OF LONGITUDINAL IMAGE ACQUIRED AT C2
ANATOMICAL LEGEND FOR C2 LOCATION IN LONGITUDINAL
DOPPLER IMAGES ACQUIRED AT C2 OF KEY VESSELS
- The infraorbital artery is usually easier to find, and power doppler is usually unnecessary. But you can occlude it if you apply to much pressure with the probe, so be careful!
- Remember to slightly angulate your probe superiorly to visualize the infraorbital foramen, which is also angulated inferiorly from the skull.
- If you see Doppler flow above the LAO/LLS muscles, you are likely viewing the angular vein and not the infraorbital artery. Identifying these muscles is useful for this reason.