Craniosynostosis - Phenotype - Plagiocephaly - Anterior Plagiocephaly

Anterior Plagiocephaly

Anterior plagiocephaly is a clinical description of unilateral coronal synostosis. Children born with unilateral coronal synostosis develop due to compensatory mechanisms a skew head; a plagiocephaly.

The sagittal suture ‘divides’ the coronal suture in two halves; unilateral meaning that either the right side or the left side to the sagittal suture is fused. This fact immediately raises an important point. Unlike closure of the sagittal or the metopic suture, right and left are not the same in unilateral coronal synostosis. This asymmetry shows in the skull deformity, as well as in the facial deformity and the complications.

This time, the skull deformity can only partly be predicted using Virchow’s law. Growth is arrested in the plane perpendicular to the fused suture and the forehead is flattened, but only at the ipsilateral side of the head. Ipsilateral indicates the same side of the head as where the suture is closed. Compensatory growth occurs in a parallel plane, as well as in a perpendicular plane. An increase in growth at the metopic and the sagittal suture accounts for the parallel plane and will result in bulging at the temporal fossa and an increase in width of the skull. Compensatory growth in the perpendicular plane occurs on the side of the head with the patent coronal suture, the contralateral side. Half of the forehead will bulge forwards as a result.

Assessment of the skull from a top view shows asymmetry of the frontal bones, an increased width of the skull and a forward displacement of the ear at the ipsilateral side of the head. Assessment of the skull from a frontal view will show asymmetrical features of the face, including a displacement of the chin point of the jaw and a deviation of the tip of the nose. The chin point is located more to the contralateral side of the head, due to the ipsilateral forward displacement of the temporomandibular joint together with the ear. The tip of the nose will also point towards the contralateral side. Complications based on the skull deformation include malocclusion of the jaw and in as many as 90% — a subtle form of — strabismus, the last being caused by the asymmetrical placement of the orbits.