In a cephalic trim, the superior aspects of the lower lateral cartilages are removed. In non-anatomical terms, it affects the area just above your nasal tip. It is used to slightly elevate the nasal tip and to remove bulk from this area in a boxy or bulbous nose. Surgeons need to be careful to leave enough cartilage behind to prevent collapse; for this reason I will actually use a set of calipers to measure the cartilage while in the operating room to ensure I don't take too much. Good luck!
Cephalic trimming is a step in Rhinoplasty frequently done to reduce the width of the Alar cartilage and to make the Nasal tip look better specially in wide amorphous tip but their is a risk if too much of the lateral crus is removed by Cephalic trimming it can cause pinched nose and Alar collapse. Many surgeons are now using Alar flaps where the cephalic portion of excess lateral crus is folded which reduces the width of cartilage and at the same time strengthens the remaining cartilage