Biparietal osteodystrophy.

Following an exhaustive literature review of 126 cases, a personal series of 8 instances is presented. The following inferences are drawn: 1) the condition is not an anatomical variant, but a pathological lesion. 2) the lesion occurs in all races, and at all latitudes; its prevalence can be estimated to range between 0.4 and 0.5%. 3) the lesion occurs predominantly in females (sex ratio male: female = 1 : 2.5) and after the age of 60. 4) histological evidence indicated erosion of the external table, compensated by remodeling of the diploe, with resultant loss of the diploe. 5) Neither senility nor senescence, nor chronic trauma, nor muscular traction, nor inflammation, can explain the lesion, its symmetry, its site or its age/sex predilection.