The hair-on-end sign.

@article{Hollar2001TheHS,
  title={The hair-on-end sign.},
  author={M A Hollar},
  journal={Radiology},
  year={2001},
  volume={221 2},
  pages={
          347-8
        }
}
The skull alterations are due to overactivity of the red marrow in response to anemia. This marrow hyperplasia widens the diploic space and thins the outer table. There is trabecular destruction with thickening of the residual trabeculae. The trabecular pattern within the diploe may sometimes be arranged perpendicular to the curvature of the cranial vault. The alternating opaque, thickened trabeculae and radiolucent marrow hyperplasia produce the hair-on-end appearance (3).