Ruptured Intracranial Dermoid Cyst

First panel: CT images reveal a fat-density mass (yellow arrows) in the midline of the posterior fossa with a thin rim of calcification (yellow arrowhead). Multiple very low density fat droplets are seen in the ventricles (red arrows) and subarachnoid spaces (red arrowheads).

Second panel: Axial T1 MR images show similar findings. Fat is shown as high attenuation on T1WI.

Intracranial Dermoid Cyst

• Rare, 0.04-0.6% of all intracranial tumors
• Occurs because of inclusion of ectoderm cells at the time of neural groove closure between 3rd and 5th week of embryonic life
• Benign, but can result in complication such as rupture
• Squamous epithelial capsule
• Cyst contains dermal elements i.e. sebaceous glands, sweat glands, hair follicles (presence of sebaceous and sweat glands differentiate this entity from epidermoid cyst)
• Midline, usually in posterior fossa or suprasellar but can be in at the base of frontal lobe or temporal lobe

Ruptured Dermoid Cyst

• Rare
• Dissemination of intracystic contents into subarachnoid space and ventricles
• Contents are thick, yellowish material (desquamated epithelium, sebaceous gland secretions, fat, oil, hair)
• In one report of 8 patients, most common clinical presentations are headache and seizures
• On imaging, fat content is seen in subarachnoid space and ventricle, may show fat-fluid level in ventricles, the primary mass has fat density and shows no or minimal enhancement

Our case - 18-year-old man, post head injury, with a ruptured posterior fossa dermoid cyst.

Reference:

Liu JK, Gottfried ON, Salzman KL, et al. Ruptured intracranial dermoid cysts: clinical, radiographic, and surgical features. Neurosurgery 2008;62:377-384.