Anatomic variations of the nasolabial fold.

The nasolabial fold varies considerably from person to person. Three main groups may be distinguished: convex, concave, and straight. It is the muscles of smiling that are directly responsible for the shape and depth of the fold, and in their absence of function, as in facial palsy, the nasolabial fold disappears. Cadavers were selected in accordance with the nasolabial fold they presented and were dissected to analyze the difference in underlying anatomy between one fold shape in one cadaver and another fold shape in another. The study demonstrates that the nasolabial fold is the result of a conflict between soft and dynamic tissues of the middle face or an interaction between the skin and fat envelope on one side and the underlying muscles on the other. The greater this conflict, the more excess there is of cheek skin and the more pronounced a nasolabial fold. The mechanism that creates the nasolabial fold and the anatomy of the fold are described in this paper.