9.06: Zone C4 – Inferior Lateral Region
YOUR ASSIGNMENT FOR THIS LESSON
✅ Step #1: Review all content below.
✅ Step #2: Image the C4 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 C4
STANDARD C4 ORIENTATION:
TRANSVERSE
The intersection of the vertical line from lateral canthus to the horizontal line from the inferior alar groove is the location of C4.
- This area is a transition from the zygoma into the soft tissue of the cheek. Start by identifying the border of the zygoma deep at C4.
- Just superficial to the bony border you will see a hypoechoic region which corresponds with the zygomaticus major.
- Deep and medial to the bony border is deep medial cheek fat.
- The zygomatic muscles can be very hard to differentiate from the superficial and deep medial cheek fat. Having the patient smile while visualizing suspected muscle can help identify this muscle. Observe for contraction under movement.
EXAMPLE OF TRANSVERSE IMAGE ACQUIRED AT C4
ANATOMICAL LEGEND FOR C4 LOCATION IN TRANSVERSE
KEY VESSELS IN THE REGION
DOPPLER IMAGES ACQUIRED AT C4 OF KEY VESSELS
- In this area you will most commonly identify superficial perforator vessels, but you need to turn your color doppler to -2cm/sec or use power dopper to detect the relatively slow flow in these vessels.
- If you detect vessels in the deep medial cheek fat you are likely seeing branches of the transverse facial artery, or the infraorbital artery in the form of the zygomatico-malar branch.
