Progressive bilateral thinning of the parietal bones.

Observation of a case of progressive bilateral parietal thinning within a period of 14 years induced us to study skull films of 3,636 consecutive patients. Parietal thinning was found in 86 patients (2.37%). It was more common in women, with a sex ratio of 1:1.9. The mean age of the females was 72 years, and that of the males 63 years. Previous skull films of 25 of these patients were available and showed progression in 10. It is concluded that parietal thinning is a slowly progressive disease of middle-aged and old patients and is not an anatomical variant or congenital dysplasia of the diploe.