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
History and etymology
The radiological pattern of intradiploic epidermoids was first described by Cushing in 1922.
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.
- bone-forming tumours
- cartilage-forming tumours
- chondromyxoid fibroma
- fibrous bone lesions
- bone marrow tumours
- other bone tumours or tumour-like lesions
- aneurysmal bone cyst
- benign fibrous histiocytoma
- giant cell tumour of bone
- Gorham massive osteolysis
- haemophilic pseudotumour
- intradiploic epidermoid cyst
- intraosseous lipoma
- musculoskeletal angiosarcoma
- musculoskeletal haemangiopericytoma
- primary intraosseous haemangioma
- simple bone cyst
- impending fracture risk
- 1. Osborn AG, Salzman KL, Barkovich AJ. Diagnostic Imaging. Lippincott Williams & Wilkins. (2009) ISBN:1931884722. Read it at Google Books - Find it at Amazon
- 2. Krupp W, Heckert A, Holland H et-al. Giant intradiploic epidermoid cyst with large osteolytic lesions of the skull: a case report. J Med Case Rep. 2012;6 (1): 85. doi:10.1186/1752-1947-6-85 - Free text at pubmed - Pubmed citation
- 3. www.ajns.paans.org. Forbidden. Read relevant article. Accessed on 19/01/2016
- 4. Osborn AG, Preece MT. Intracranial cysts: radiologic-pathologic correlation and imaging approach. Radiology. 2006;239 (3): 650-64. doi:10.1148/radiol.2393050823 - Pubmed citation