MR imaging of epidermoid cysts

Nine patients with epidermoid cysts, five of them pathologically proved, were evaluated with MR imaging. Six patients also had CT. The cases were reviewed to evaluate the MR appearance of epidermoid cysts and to compare the MR findings with those of CT. The epidermoid cysts demonstrated low-signal intensity on T1-weighted MR images and hyperintensity on T2-weighted images. In five cases the cysts appeared heterogeneously iso- to hyperintense on the intermediate echo, and were surrounded by a thin rim of high signal intensity, which we believe was caused by encased CSF. The CT scans showed the cysts as low-density, well-demarcated lesions that do not enhance after infusion with contrast material. We conclude that MR is superior to CT in the evaluation of epidermoid cysts and is particularly useful in surgical planning.