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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

Note: Clip is sped up.

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.

QUICK TIP
  • 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

Standard image acquired at C4. (Transverse | Left side is patient's left). See key below for lables.*

ANATOMICAL LEGEND FOR C4 LOCATION IN TRANSVERSE

*Standard image acquired at C4 labeled with key anatomical structures.
Superficial Fat Compartments
Deep Fat Compartments

KEY VESSELS IN THE REGION

DOPPLER IMAGES ACQUIRED AT C4 OF KEY VESSELS

Play Video
QUICK TIP
  • 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.

DO IT YOURSELF CHECKLIST

Structures to Identify on Ultrasound for C4

Once you have completed this checklist, mark this part of the lesson as complete.