Cleft Lip Embryology — MFDS Part 1 MCQ

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ModerateAnatomy (Head & Neck)Cleft Lip EmbryologyMFDS Part 1

A newborn has a unilateral cleft of the upper lip lateral to the philtrum, with an intact palate. Failure of fusion between which embryological structures most directly accounts for this defect?

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Correct answer: D — Medial nasal and maxillary prominences

The correct answer is D. The philtrum is derived principally from the merged medial nasal prominences, whereas the lateral parts of the upper lip develop from the maxillary prominences. A unilateral cleft lateral to the philtrum therefore reflects failure of fusion between the medial nasal and maxillary prominences on the affected side. Failure of the two palatal shelves to fuse causes a cleft of the secondary palate, which is excluded by the intact palate. Abnormal union of the maxillary and mandibular prominences is associated with a transverse facial cleft. Failure involving the paired medial nasal prominences produces a rare median cleft, while the lateral and medial nasal prominences are primarily involved in development around the nasal pit rather than the characteristic lateral cleft described here.

Reference: Walsh K, Foy C. Surgical Repair of Cleft Lip: Comparison of Neonatal and Standard Timing in a Systematic Review. Cureus. 2025;17(9):e92858. Embryology statement in abstract. https://pubmed.ncbi.nlm.nih.gov/16292776/