OK- not a musculoskeletal case. But a nice one anyway. Sagittal T1W, axial diffusion, axial T2W, axial FLAIR and axial T1W.
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Epidermoid cyst. Extra-axial. 1% of intracranial lesions. Rarely rupture compared with dermoid cysts (which cause chemical meningitis). Likely congenital- and grow very slowly. 


Read about it here.