Cleft Lip and Palate

Abstract

Clefts of the lip and palate occur as a result of the failure of fusion of the maxillary and frontonasal processes during embryonic development. At around 5 weeks of gestation, the palate anterior to the incisive foramen fuses progressively through the anterior hard palate, alveolus and lip. The failure of this fusion process produces a cleft lip, which can be either unilateral or bilateral. At about 7 weeks of gestation, a fusion process moves caudally from the incisive foramen through the hard palate and the soft palate to the tip of the uvula. Failure of this fusion process produces a cleft palate. The part of the palate anterior to the incisive foramen that fuses first is often referred to as the primary palate for that reason, but occurs as part of a cleft lip, not a cleft palate. A midline cleft of the upper lip is a very unusual anomaly and is often associated with other midline developmental problems such as absence of the corpus callosum and holoprosencephaly (failure of the hemispheres to divide).