Intracranial "white" epidermoid tumours - An imaging approach and systematic review

Intracranial epidermoid cysts are rare congenital inclusion cysts that can be divided into the classical "black epidermoid" and the exceedingly rare "white epidermoid". White epidermoids are often misdiagnosed because they have different imaging features compared to black epidermoids. There is a paucity of imaging review on white epidermoids. We hereby derive an explanation for the variable imaging features of white epidermoids and propose an imaging approach to distinguish white epidermoids from black epidermoids.

We conducted a review of white epidermoids in PubMed and Cochrane databases based on PRISMA principles. Qualitative analysis was carried out on the selected cases of white epidermoids, focusing on pathogenesis, imaging features, treatment and prognosis.

Out of 1281 studies, we identified 26 full-text articles, comprising 68 patients with white epidermoid cysts, including an illustrative case example from our institution. White epidermoids have completely different MRI signals compared to the classical black epidermoids. Owing to tumour adhesions to the surrounding structures, there is a higher risk of leakage of white epidermoid content during surgery, causing severe aseptic meningitis. We demonstrate an approach to explain the variable imaging features of white epidermoids based on their cyst content - white epidermoids with low T2 signals content often contain high protein levels and viscosity, while those with high T2 signals contain blood products.

During preoperative planning, it is important to identify white epidermoids. Extensive neurovascular damage should be avoided during surgery given the favourable prognosis of the epidermoids regardless of the extent of tumour resection.