Craniolacunia and the Development of the Fetal Calvaria: An Autopsy Series With Clinical and Histological Analysis

Craniolacunia, also known as lückenschädel, is a congenital abnormality of the calvaria featuring well-circumscribed areas of marked thinning, interspersed with more-normal bone. It is most commonly associated with myelomeningocele and/or Chiari 2 malformation. Records, photographs, and histologic sections were reviewed from 13 autopsy cases with craniolacunia. To investigate normal calvarial development, 23 parietal bone samples from fetuses/infants of 16–42 weeks gestation were examined. Parietal bone development had reproducible morphologic stages. Bone thickness increased with gestational age, while osteoblast numbers decreased. Craniolacunia was mainly seen in neonates. Five patients had Chiari 2 malformation, 1 had hydrocephalus, and 2 had other structural CNS abnormalities. One had trisomy 18. Four had no congenital abnormalities. Two sustained intrapartum skull fractures. Histologic sections were available in 5 cases. Lacunae in term infants had architecture similar to normal calvaria at 16–20 weeks. Adjacent bone had age appropriate architecture but increased osteoblast numbers. This is the largest autopsy series of craniolacunia and first systematic histologic analysis of craniolacunia and the developing fetal calvaria. Decreased cerebrospinal fluid pressure, due to myelomeningocele or other structural abnormality, may promote craniolacunia development. The risk of intrapartum fracture through lacunae emphasizes the continued clinical relevance of this diagnosis.