Intradiploic epidermoid cyst

Last revised by Dr Yuranga Weerakkody on 21 Jul 2022

Intradiploic epidermoid cysts refer to epidermoid cysts that occur in the diploë of the skull.

Painless slowly progressive scalp swelling.

  • epidermoid cysts may be congenital (most common, arising from ectodermal inclusion during neural tube closure and subsequently remain within the cranial bones) or acquired (e.g. post-surgical or post-traumatic implantation) 4
  • intradiploic epidermoids are less frequent than the intradural variety 1

Intradiploic epidermoids occurs within the frontal, parietal, occipital and sphenoid bones, as well as the spine 1.

  • rounded or lobulated area of bone destruction, well-delineated sclerotic scalloped margins
  • non-enhancing hypodense lesion with sharply demarcated bony defects and zones of calcifications
  • it may alter the outer and/or inner tables of the skull (the inner table more than the outer)
  • T1: slightly hyperintense to the CSF
  • T2: isointense/hyperintense to the CSF
  • FLAIR: hyperintense to the CSF space
  • DWI: restricted diffusion with characteristic hyperintensity
  • T1C+: none

The first intradiploic epidermoid cyst was reported by J Müller in 1838 5.

The radiological pattern of intradiploic epidermoids was first described by Cushing in 1922.

Consider:

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Cases and figures

  • Case 1: CT
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  • Case 1: DWI
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  • Case 2
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  • Case 3
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  • Case 4: with external angular orbital extension
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  • Case 5: orbital intradiploic epidermoid cyst causing proptosis
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  • Case 6
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  • Case 7: on transcranial ultrasound
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  • Case 8
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