Dermoid Cyst

            Dermoid cysts have both dermal and epidermal derivatives, accounting for their more varied histologic and MR appearance. They are primarily midline lesions, occurring in the pineal and suprasellar regions. Dermoids have some distinctive features on MR. They tend to be heterogeneous owing to the multiple cell types within them. Fatty components are common, producing high signal on T1-weighted images. On axial and sagittal scans, a fat-fluid level may be seen, or a level between fat and matted hair within the cyst. Rupture of a dermoid and leakage of cyst contents into a ventricle or subarachnoid space may produce an ependymitis or meningitis, respectively.

            Lipomas are also midline lesions and are often associated with partial or complete agenesis of the corpus callosum. Occasionally, an incidental lipoma will be found in the region of the quadrigeminal plate or cerebellopontine angle.  

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