Hair on end sign (mnemonic)

Last revised by Mohammad Taghi Niknejad on 17 Aug 2024

The hair on end sign refers to a radiographic appearance of the diploic space of the skull vault which results from a thickening of trabeculae as the diploic space expands. These trabeculae are perpendicular in orientation, interspersed by radiolucent marrow hyperplasia along with skull vault.

It is classically described with plain skull radiographs, although it can also be appreciated on CT or MRI 3. Causes include:

A useful mnemonic to remember the various causes of this sign is:

  • HI NEST 4

Mnemonic