What Is a Lambdoidal Suture?

The lambdoidal suture is a fibrous joint located on the skull just below the occipital bone that forms the rounded portion of the back of the skull. This suture joint connects the occipital bone with the parietal and temporal bones. Connecting material in the lambdoidal suture is made of ossified cells and a dense fibrous material called sharpey’s fibres, and it is complete with vascularization and nerve fibers.

At birth, the infant skull consists of 44 different pieces of bone connected by dense fibrous connective tissue. These soft areas of fibrous tissue are called fontanels. As the child grows, portions of the fontanel become ossified, or harden, joining the bony pieces and forming the five separate suture joints of the skull. If cranial growth is uneven or the lambdoidal suture does not form correctly, the skull may appear misshapen. Once the child has reached adulthood, only 22 bones comprise the skull.

The lambdoidal suture is composed of both serrated and squamosal sutures. Serrated portions of the joint have jagged tooth-like projections that allow for the contraction and expansion of the cranial cavity. Squamosal sutures feature a smooth overlapping edge at the suture joint. Overlapping portions of the joint may resemble closely layered scales.

A disorder caused by the abnormal fusion of the lambdoidal suture is called posterior plagiocephaly, or lambdoid synostosis. It causes one side of the head to appear flatter than the other side. A small bump is present on the skull behind the ear on the side of the head with the fused joint. Several members of a family often develop the improperly fused suture joint, indicating there may be a genetic link to the cause of the condition.

Diagnosis of a fused lambdoidal suture may occur after a visual examination of the skull by a physician. In addition to the flat area of the skull, the ear on the same side as the fused suture may be located in a slightly different spot than normal. Computerized tomography (CT) scans are sometimes used to confirm the fusion of the lambdoidal suture.

A surgical procedure to correct the improperly fused lambdoidal suture is not usually necessary to restore a symmetrical appearance. Many young patients with this condition are able to have the skull deformity corrected by the use of a headband-like device. It provides a consistent gentle pressure that over time reshapes the flat side of the skull.