wormian

Wormian bones, also known as sutural bones, are extra bone pieces that occur within the sutures of the skull. They are small, irregular ossicles that can vary in number, size, and shape. Most commonly they appear along the lambdoid and sagittal sutures but may be found at any cranial suture or fontanelle. They are often discovered incidentally in imaging or during autopsy and can persist from infancy into adulthood.

The term derives from Ole Worm, a 17th-century Danish anatomist who described these bones in human skulls. Wormian bones are not a distinct disease; rather, they represent a normal anatomic variant in some individuals, the frequency of which varies across populations and age groups.

Wormian bones may occur in isolation or in multiples along sutures. They can be bilateral or unilateral and their shapes range from circular to irregular or worm-like. While many individuals with Wormian bones are asymptomatic, an increased number or particular patterns of Wormian bones can be associated with certain congenital conditions and skeletal dysplasias, such as osteogenesis imperfecta and cleidocranial dysostosis, and may be seen in some cases of craniosynostosis or metabolic bone disorders.

In radiologic practice, Wormian bones are identified as discrete ossicles along cranial sutures. It is important to distinguish them from skull fractures or sutural diastasis, especially in the setting of trauma. Overall, Wormian bones are a recognized anatomical variant with variable clinical significance.