Trigonocephaly involves fusion of the metopic suture. The metopic suture runs from the top of the head, at the fontanel or soft spot, down the center of the forehead to the nose. It is different from the other sutures of the skull because it is the only one that normally begins closing in infancy. A ridge can easily be seen running down the center of the forehead and the fontanel is usually absent, or closed. In looking straight on at your child, in addition to seeing a ridge running down the center of the forehead, the forehead will look narrow, and the child's eyes are usually spaced closer together than is normal. When viewed from above the forehead has a triangular shape, like the bow of a boat.

The incidence of trigonocephaly is somewhere between one in 2,500 to one in 3,500 births. The reason for this range is that it is sometimes difficult to determine if a child has trigonocephaly or not. Some children may be very mildly affected and do not require treatment. Trigonocephaly has been reported to occur when mothers have taken Valproic Acid for seizures.

Many children may just have a ridge running down the center of their forehead suggesting that the metopic suture has closed early, without producing the triangular-shaped forehead. Only those children who have overt trigonocephaly need treatment. Children with an isolated ridge running down their foreheads do not require surgery (see Publications, Book Chapters #3, 2002). The treatment for this condition is discussed in the treatment section.