Question

Which fontanelle is the last to close?

• A. Anterolateral
• B. Anterior
• C. Lateral
• D. Occipital

Hint:

The diamond-shaped anterior fontanelle closes at 18 to 24 months.

Answer 1

The Correct Option is B

Step 1: Fontanelles are the soft membranous gaps between the developing skull bones, and they close in a predictable sequence after birth as the bones ossify.
Step 2: The posterior (occipital) fontanelle closes first, by about 2 to 3 months; the sphenoidal fontanelle closes around 6 months; the mastoid fontanelle closes between 6 and 18 months; and the anterior fontanelle closes last, between about 18 and 24 months. Therefore the anterior fontanelle is the last to close.
Step 3: Why the others are wrong. The anterolateral (sphenoidal) and posterolateral (mastoid) fontanelles close earlier than the anterior one. The occipital (posterior) fontanelle is actually the first to close, the opposite of what is asked.