White epidermoids are a rare type of epidermoid cyst that do not follow the usual near-CSF density and signal intensity on CT and MR respectively. To make matters worse the literature uses the term inconsistently, although generally the 'white' refers to the T1 weighted imaging appearance.
In some cases, the intrinsic high T1 signal is due to a high protein content, which renders them relatively hyperattenuating on CT 3. In this case, T2 signal can vary from hyper to hypointense.
Alternatively, the high T1 signal can be due to high lipid content (mixed triglycerides and no cholesterol), which are associated with fat density on CT 3,4. This need not be uniform and may also result in signal suppression on fat attenuated sequences.
Additionally, intrinsic high T1 signal can be seen in rare instances of hemorrhage into the cyst 3.
- 1. 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
- 2. Dähnert W. Radiology Review Manual. Hubsta Ltd. (2007) ISBN:0781766206. Read it at Google Books - Find it at Amazon
- 3. Chen CY, Wong JS, Hsieh SC et-al. Intracranial epidermoid cyst with hemorrhage: MR imaging findings. AJNR Am J Neuroradiol. 2006;27 (2): 427-9. AJNR Am J Neuroradiol (full text) - Pubmed citation
- 4. Horowitz BL, Chari MV, James R et-al. MR of intracranial epidermoid tumors: correlation of in vivo imaging with in vitro 13C spectroscopy. AJNR Am J Neuroradiol. 1990;11 (2): 299-302. AJNR Am J Neuroradiol (abstract) - Pubmed citation