Normal variants and congenital anomalies in the region of the obelion

AJR Am J Roentgenol. 1976 Sep;127(3):487-94. doi: 10.2214/ajr.127.3.487.


A number of anatomic bony variants and several congenital anomalies are known to occur at the level of the obelion, that is, in the posterior interparietal region of the head, a short distance in front of the lambda. Among them are: (1) remnants of the embryonic parietal incisura, including parietal fissure, small and large parietal fontanelle, obeliac bones, persistant midline parietal foramen, and small and large parietal foramina; (2) encephalomeningoceles and related defects, including true encephaloceles, herniation of midline intracranial cysts (diencephalic and Dandy Walker cyst), epicranial arachnoid cysts, and scalp defects with ectopic glial tissue; and (3) congenital scalp and skull defects (cutis aplasia congenita). A review of these defects is presented with some illustrative examples not previously reported.

MeSH terms

  • Adolescent
  • Brain Diseases / diagnostic imaging
  • Central Nervous System Diseases / diagnostic imaging
  • Child
  • Child, Preschool
  • Cysts / diagnostic imaging
  • Encephalocele / diagnostic imaging
  • Humans
  • Infant
  • Infant, Newborn
  • Radiography
  • Scalp / abnormalities
  • Skull / abnormalities
  • Skull / diagnostic imaging*