MRI - Annotated Images
What is this material and how could you confirm this on imaging?
The material is lipid rich. This can be confirmed on fat saturated sequences or by reviewing a CT scan and assessing density (probably around -100HU).
True or false: the material in the ventricles is composed of adipocytes (fat cells)
False. A common misconception is that dermoid cysts contain adipose tissue. This is not the case, as lipocytes are mesodermal in origin and dermoid cysts (by definition) are purely ectodermal. A dermoid cyst with adipose tissue would be a teratoma.
What is this fatty fluid composed of?
Dermoid cysts, like epidermoid cysts are lined by stratified squamous epithelium. Unlike epidermoid cysts however they also have epidermal appendages such as hair follicles, sweat and sebaceous glands. The later is responsible for the secretion of sebum which imparts the characteristic appearance of these lesions on CT and MRI.
Why is headache present in the setting of rupture?
The sebum results in an aseptic chemical meningitis.
High T1 signal material is floating on CSF in the anterior horns of the lateral ventricles (blue arrows), and multiple small droplets of T1 hyperintense material can be seen in the subarachnoid space of both hemispheres (yellow arrows).
An area of encephalomalacia (yellow dotted line) is consistent with an old left MCA territory infarct.