Hair on end sign (mnemonic)

Last revised by Dr Dai Roberts on 04 Dec 2020

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

Mnemonic

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Cases and figures

  • Case 1
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  • Case 2: in thalassemia
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  • Case 3
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  • Case 4
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  • Case 5: on MRI
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  • Case 6: thalassemia major on CT
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