The Anatomy of the Lambdoid Suture

The lambdoid suture is made up of dense, fibrous connective tissue. It is located at the back of the skull, and its function is to connect the occipital bone with the two parietal bones. It is continuous with the occipitomastoid suture, which connects the occipital bone with the temporal bones. 

This article looks at the anatomy of the lambdoid suture, its function, and associated conditions.

Anatomy

Four main cranial sutures connect the six cranial bones. The lambdoid suture is one of them. The lambdoid suture gets its name from its resemblance to the uppercase Greek letter lambda (Λ). 

Like all cranial sutures, the lambdoid suture is made up of dense, fibrous bands of tissue. It is located at the back of the skull, where it connects the occipital bone (the bone at the back of the skull) with the parietal bones (the bones at the top and sides of the skull).

Specifically, the lambdoid suture is the line that forms the top border of the occipital bone and the rear border of the left and right parietal bones. This line looks as if it has been stitched.

Function

The main function of the lambdoid suture is to connect the occipital bones with the parietal bones. It has no motor or sensory function. It is simply there to hold the bones together. 

During brain development, however, its job is also to keep a small line of space between the occipital bone and parietal bones for the skull to expand so that the brain can grow and develop properly.

The period in which the lambdoid suture has the most developmental activity is usually around three months of age, possibly due to the accelerated growth of the cerebellum at about that time.

The lambdoid remains open through childhood, typically closing by 26 years of age. After that, its job is simply to keep the bones connected.

Associated Conditions

If cranial sutures close too early—that is, before the brain is fully formed—it can lead to a condition called craniosynostosis, which causes the brain and skull to grow abnormally.

For example, the part of the skull where the suture closes too early will cause the head to stop growing in that area while it continues to grow in other parts of the skull where the sutures haven’t closed. This will cause the skull to have an abnormal shape, though the brain will grow to its usual size.

There are different types of craniosynostosis, depending on which sutures fuse together too early. These include:

• Lambdoid synostosis, which occurs when the lambdoid suture closes too early. This may cause the baby’s head to be flattened at the back (where the lambdoid suture is). It is one of the least common types of craniosynostosis.
• Posterior plagiocephaly is a medical term used to describe asymmetry in the back of the skull, such as that caused by lambdoid synostosis.

Posterior plagiocephaly and lambdoid synostosis aren’t always one and the same. While lambdoid synostosis is caused by internal factors (i.e., the lambdoid suture closes too early), posterior plagiocephaly is caused by external factors that force the head (when it’s still developing) to mold into an abnormal shape.

Posterior plagiocephaly can also be caused by lambdoid synostosis. One unique characteristic of lambdoid synostosis is that it causes the base of the head to have a tilt, and the ear on the affected side is pulled back and toward the fused suture.

For example, if the right side of the lambdoid suture (the part where the occipital bone meets the right parietal bone) closes too early, the right side of the skull will look pulled down while the left side will look tilted upward.

Treatment

Cases of lambdoid synostosis can range from mild to severe. Some cases may require surgery, usually within the first year of life.

Surgery is often recommended to reduce the cranial pressure resulting from the suture closing while the brain is still growing. It can also help correct deformations of the skull bones, such as the tilt of the skull caused by lambdoid synostosis. 

If it’s the case that the suture fusing too early is disrupting brain growth and development, early intervention may be necessary to help with developmental delays or disabilities. Ongoing monitoring of the brain and skull growth by a healthcare provider will help ensure that developmental issues are prevented and/or treated.

Keep in mind that serious interventions are not always indicated. In mild cases, special medical helmets can help mold a baby’s head into a more normal shape.

A Word From Verywell

It can be hard to get a grasp on what and where the lambdoid suture is since it is not visible to the eye. Just think of it as a line of thick tissue that connects the bone at the back of the head with those at the sides, like the stitching between quilt squares.

You normally wouldn’t talk much about the lambdoid suture outside of an anatomy class, but knowing that it has a part in brain development can be useful. If the lambdoid suture closes too early, this can mean that the skull looks misshapen and the pressure inside the skull increases as the brain’s growth is restricted.

Though a deformed skull and talk of developmental delays can be alarming, especially for new parents, it is quite common for babies to have craniosynostosis, and treatments are available to help correct deformations and developmental delays.

The bottom line is that for the most part, the lambdoid suture is nothing more than an anatomical feature, and if anything abnormal happens with it, healthcare providers know what to do to treat it.

Frequently Asked Questions

Where is the lambdoid suture?

The lambdoid suture is located at the back of the head. It forms the top border of the occipital bone and the rear border of the two parietal bones.

What does the lambdoid suture do?

The lambdoid suture is a line of dense, fibrous tissue that connects the occipital bone with the parietal bones. It is continuous with the occipitomastoid suture, which connects the occipital bone with the temporal bones.

How are craniosynostosis and the lambdoid suture related?

The lambdoid suture closes as part of normal development. However, if the lambdoid suture closes too early, it can cause lambdoid synostosis. This can lead to abnormal development as the brain is restricted from growing due to the skull bones fusing too early.

How common is lambdoid synostosis?

Lambdoid is one of the least common types of craniosynostosis.