**Core Concept**
Trigonocephaly is a congenital anomaly characterized by a triangular shape of the forehead, resulting from an abnormality in the development of the cranial sutures. Specifically, it is associated with the premature closure of a particular suture that affects the growth of the fronto-nasal region.

**Why the Correct Answer is Right**
The premature closure of the metopic suture leads to trigonocephaly. The metopic suture is a midline suture that separates the two halves of the frontal bone. Normally, this suture fuses together by the age of 6-12 months. However, its premature closure can result in an abnormal triangular shape of the forehead. This is because the metopic suture plays a crucial role in the growth of the fronto-nasal region, and its closure can lead to an imbalance in the growth of the surrounding bones.

**Why Each Wrong Option is Incorrect**
* **Option A:** Premature closure of the sagittal suture is associated with scaphocephaly, a condition characterized by a long and narrow skull shape.
* **Option B:** Premature closure of the coronal suture is associated with brachycephaly, a condition characterized by a short and broad skull shape.
* **Option C:** Premature closure of the lambdoid suture is not a recognized cause of trigonocephaly.

**Clinical Pearl / High-Yield Fact**
It's essential to remember that premature closure of cranial sutures can result in various anomalies, including trigonocephaly, scaphocephaly, and brachycephaly. These conditions can be caused by genetic mutations, craniosynostosis, or other factors affecting skull growth.

**Correct Answer: B. Premature closure of the metopic suture leads to trigonocephaly.**