Intradiploic epidermoid cyst

Last revised by Dr Mostafa El-Feky on 12 Jun 2021

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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