Intraventricular dermoid cyst with rupture
6-month history of increasing headaches worse in the morning and associated with nausea and vomiting.
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Right intraventricular non-enhancing mixed cystic/solid lesion with fat lying antedependently within the lateral ventricles. There is direct extension into the suprasellar cistern and inferiorly into the posterior cranial fossa cisterns. The cystic component results in significant mass effect and distortion of the thalami, cerebral peduncles, midbrain and upper pons. The right middle cerebral artery is anteriorly displaced secondary to the mass. There is shift of the third ventricle to the left of up to 11mm. Incidental Tornwaldt cyst in the nasopharynx.
MRI features are most consistent with a ruptured intraventricular dermoid cyst.
An intracranial dermoid cyst is a rare benign intracranial neoplasm of ectodermal origin. Dermoid cysts are most commonly found in the midline such as the posterior cranial fossa but may also involve the spine.
Unlike the more common epidermoid cyst, also of ectodermal origin but entirely composed of keratinized squamous epithelium, dermoid cysts also contain dermal appendages such as hair follicles, sebaceous and sweat glands.
Radiologically, this case demonstrates a good example of Type 1 chemical shift artifact which arises due to the difference in resonance frequencies of hydrogen nuclei in fat and water. This causes slight misregistration of the signal from fat in the frequency encoding direction, resulting in a bright band on one side and a dark band on the other side of a fat-soft tissue interface.