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 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
- 1. Miller TT. Bone tumors and tumorlike conditions: analysis with conventional radiography. Radiology. 2008;246 (3): 662-74. Radiology (full text) - doi:10.1148/radiol.2463061038 - Pubmed citation
- 2. Azam M, Bhatti N. Hair-on-end appearance. Arch. Dis. Child. 2006;91 (9): 735. Arch. Dis. Child. (full text) - doi:10.1136/adc.2006.100032 - Free text at pubmed - Pubmed citation
- 3. Hollar MA. The hair-on-end sign. Radiology. 2001;221 (2): 347-8. Radiology (full text) - doi:10.1148/radiol.2212991231 - Pubmed citation
- 4. Dähnert W. Radiology Review Manual. (2011) ISBN:1609139437. Read it at Google Books - Find it at Amazon