What areas of the nose are resected when “cephalic trim” is performed?

Cephalic is a term that means closer to the head, while caudal means closer to the tail. A cephalic trim of nasal tip cartilage, is removal of the top portion of the alar tip cartilages typically to achieve narrowing and rotation of the nasal tip. Thank you. Dr Joseph 

Superior or the upper parts of the lower lateral cartilages are trimmed in this technique. This is typically performed in wide / bulbous noses / boxy tips and also the improve the definition and rotation of the nasal tip. 
These are carefully performed procedures. Too little resection may not give much improvement. Too much resection however can weaken the tip and can also cause collapse. Symmetry at the end of it has to be paramount. 
These are challenging techniques so do discuss them with an experienced and board certified facial plastic surgeon.
Best Wishes

A cephalic trim is a technique used to refine the tip of the nose.  Cephalic refers to the upper portion of the lower lateral cartilages, and by resecting that upper portion, the tip of the nose can be lifted and narrowed.  One must by careful to leave some of the lower lateral cartilages intact, because too much resection can lead to airway problems and a pinched tip.