Wormian bones (a.k.a. intrasutural bones) is the name given to the additional small bones sometimes found between the cranial sutures of the bones of the skull vault, most commonly in relation to the lambdoid suture. Some reserve the term Wormian bones to just the intrasutural bones proximate to the lambdoid suture.
Some consider them abnormal only if greater than 10 in number.
The reported incidence is variable, ranging from around 10% (in Caucasian skulls) and 40% (in Indian skulls) to 80% (in Chinese skulls) ref. In general, males are more frequently affected than females ref.
Their associations are various, and include:
- osteogenesis imperfecta
- kinky hair syndrome
- cleidocranial dysostosis
- otopalatodigital syndrome
- primary acroosteolysis (Hajdu-Cheney syndrome)
- Down syndrome
Wormian bones can also be idiopathic (anatomical variant).
A useful mnemonic is PORKCHOPS.
- lambdoid suture: most common
- lambda (also known as the pre-interparietal or inca bone)
- pterion: up to 12%; former anterolateral fontanelle (also known as the epipteric bone or pterion ossicle)
- sagittal and coronal sutural bones: uncommon
History and etymology
These bones are named after the person who first described them:
- Ole Worm (1588-1654), Danish physician, theologian and antiquary, Copenhagen, Denmark.
- 1. S.B. Nayak "Multiple Wormian bones at the lambdoid suture in an Indian skull" Neuroanatomy (2008) 7: 52–53
- 2. S.B. Nayak and K.V. Soumya "Unusual sutural bones at pterion" International Journal of Anatomical Variations (2008) 1: 19–20
- 3. Jones KL, Smith DW. Smith's recognizable patterns of human malformation. W.B. Saunders Company. (1997) ISBN:0721661157. Read it at Google Books - Find it at Amazon
- anatomic position
- Terminologia Anatomica
- anatomic variants
- regional anatomy
- systems anatomy
- labelled imaging anatomy cases
- macroscopic structure
- microscopic structure
- bone growth
- bones types
- nutrient foramen
- blood vessels