The coronal suture is a fibrous joint in an infant’s developing skull, connecting the frontal bone to the two parietal bones. This suture extends across the top of the head from one side to the other, much like the placement of a headband. These sutures intersect at soft spots known as fontanelles. The largest of these is the anterior fontanelle, located at the junction of the coronal, sagittal, and frontal sutures.
The Role of the Coronal Suture in Development
The primary purpose of the coronal suture relates to birth and early life. Its flexible nature allows the bony plates of the skull to shift and overlap. This molding capability helps the infant’s head to navigate the narrow birth canal during delivery.
Following birth, the suture’s role transitions to accommodating the significant and rapid expansion of the brain. During infancy and early childhood, the brain undergoes its most substantial growth phase. The open suture permits the skull to expand uniformly, preventing constriction of the developing brain.
Timeline for Closure
Unlike the fontanelles, which close within the first 18 to 24 months after birth, the coronal suture remains open for a much longer period. The process of the suture fusing and turning into solid bone, known as ossification, is a gradual one. This fusion does not begin until a person is in their early twenties.
The complete closure of the coronal suture is a slow process that concludes around the age of 24. This extended timeline ensures the skull can accommodate brain growth throughout childhood and adolescence.
Complications from Premature Fusion
When the coronal suture fuses prematurely, it results in a condition called coronal craniosynostosis. This early ossification prevents the skull from growing perpendicular to the fused suture. The brain’s continued growth forces the skull to expand in other directions, leading to an abnormal and asymmetrical head shape. This condition occurs in approximately 1 in 10,000 live births.
The physical signs of unilateral coronal synostosis, where one side fuses early, are distinct. An infant may present with a flattened forehead and a raised eye socket on the affected side. The unaffected side may bulge forward as a form of compensatory growth, and the root of the nose can deviate toward the fused side. This abnormal skull growth can restrict brain development and, in some cases, lead to increased pressure inside the skull.
If these physical characteristics are observed, a medical evaluation is necessary to confirm the diagnosis and determine the best course of action. Surgical intervention is often recommended to correct the skull’s shape, which relieves pressure and allows for the brain’s continued, unrestricted development.