Intradiploic epidermoid cyst: Report of two cases with typical CT and MR imaging features

We studied 2 patients with large expansive and osteolytic lesions of the skull on CT, with characteristics suggestive of intradiploic epidermoid cysts. It was the purpose of our work to study the MR-imaging characteristic of these lesions. Both lesions proved to have the same MR-imaging characteristic than epidermoid cysts elsewhere in the intracranial compartment. The lesions were inhomogeneously hypointense on T1-weighted images, inhomogeneously hyperintense on T2-weighted images and on FLAIR, without signal attenuation. The signal intensity was high on diffusion-weighted images reflecting diffusion restriction in one patient with low ADC-value and a factor T2-shine through in the other patient with an intermediate ADC-value. The behaviour of the lesion on a CISS sequence, performed in one patient was also similar to other epidermoid cysts, but this proved less relevant at this location.