‘White’ Epidermoid Cyst

A probable case of a white epidermoid, an unusual version of an epidermoid cyst, in that as opposed to typical epidermoids, it is of much higher intensity than CSF on T1WI, hyperintense to grey matter. This is due to high triglycerides & unsaturated fatty acids.
Although not marked, on DWI sequences this lesion is much more restricted than CSF, and does not null on FLAIR.
In this case not only is the epidermoid of the ‘white’ variety, but it is also extradural, seen to remodel the inner table, with sclerotic margin. Only 10% of epidermoid cysts are extradural, and can be seen anywhere.
The lesion had been found incidentally after a minor head trauma scan, and has remained stable in appearance over a number of years.
References:
1. Osborn A, Blaser S, Salzman K. Diagnostic Imaging: Brain. Amirsys 2004
2. StatDx
Credit: Dr Frank Gaillard
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