Lacunar skull, (a.k.a. Luckenschaedel and crainolacunia), is a finding seen in association with myelomeningocele, myelocele, and encephalocele. It is the result of dysplasia of the membranous bones of the calvarium and can be seen as early as 8 months gestation and usually persists until the age of 1-3 months but typically has resolved by age 6 months. The normal development of the membranous skull requires distension of the developing brain and ventricular system. The skull develops from ossification centers in each cranial plate. As the brain expands, collagen bundles in each center are drawn out in an orderly radial manner. Ossification of the collagen bundles also takes place radially. In patients with lacunar skull, the collagen bundles are disorganized and form whorls with varying thickness of fibrous tissue between them. Ossification of the collagen bundles occurs in a disorderly manner producing lacunar skull. This is independent of the presence of hydrocephalus. It should not be confused with normal convolutional markings seen in the vault during the period of rapid brain growth (3 to 7 years).