Bregma


The bregma is the anatomical point on the skull at which the coronal suture is intersected perpendicularly by the sagittal suture.

Structure

The bregma is located at the intersection of the coronal suture and the sagittal suture on the superior middle portion of the calvaria. It is the point where the frontal bone and the two parietal bones meet.

Development

The bregma is known as the anterior fontanelle during infancy. The anterior fontanelle is membranous and closes in the first 18-36 months of life.

Clinical significance

Cleidocranial dysostosis

In the birth defect cleidocranial dysostosis, the anterior fontanelle never closes to form the bregma.

Surgical landmark

The bregma is often used as a reference point for stereotactic surgery of the brain. It may be identified by blunt scraping of the surface of the skull and washing to make the meeting point of the sutures clearer.

Neonatal examination

Examination of an infant includes palpating the anterior fontanelle. It should be flat, soft, and less than 3.5cm across. A sunken fontanelle indicates dehydration, whereas a very tense or bulging anterior fontanelle indicates raised intracranial pressure.

Height assessment

Cranial height is defined as the distance between the bregma and the midpoint of the foramen magnum. This is strongly linked to more general growth. This can be used to assess the general health of a deceased person as part of an archaeological excavation, giving information on the health of a population.

Etymology

The word "bregma" comes from the Ancient Greek βρέγμα, meaning the bone directly above the brain.