Intradiploic epidermoid cyst

Intradiploic epidermoid cysts represent epidermoid cysts that occur in the intradiploic space 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, sphenoid bones as well as the spine 1.

  • rounded or lobulated  area of bone destruction, well delineated sclerotic scalloped margins
  • nonenhancing hypodense lesion with sharply demarcated bony defects and zones of calcifications
  • it may alter the outer 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 radiological pattern of intradiploic epidermoids was first described by Cushing in 1922.

Bone tumours

The differential diagnosis for bone tumours is dependent on the age of the patient, with a very different set of differentials for the paediatric patient.

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Article information

rID: 42420
Section: Pathology
Synonyms or Alternate Spellings:
  • Skull epidermoid cyst

Cases and figures

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    Intradiploic epid...
    Case 1: CT
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    Intradiploic epid...
    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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