Teaching Case

A 18 year- old male was admitted to the emergency department of our hospital with status epilepticus. His past history included loss of vision of the left eye at the age of five and persistent headaches for the past 10 years

A 18 year- old male was admitted to the emergency department of our hospital with status epilepticus. His past history included loss of vision of the left eye at the age of five and persistent headaches for the past 10 years. However, he had not received any medical attention until his admittance to our hospital. Computed Tomography showed a fat containing tumor with negative attenuating values in the suprasellar region, extending to the frontal fossa. The mass has peripheral calcifications. Lipid droplets are found in the subarachnoid spaces. No evidence of hydrocephalus was found. Magnetic Resonance confirmed the findings of the fat containing tumor and the fatty drops in the subarachnoid spaces.

Dermoids represent less than 1% of all intracranial tumors. Together with teratomas and epidermoids constitute the inclusion tumors of CNS. Dermoid tumors are of congenital origin and they are derived from ectoderm. They are composed of a dense fibrous capsule lined with stratified squamous epithelium. The dermoid may contain ectodermal glands such as apocrine glands and hair follicles. Teeth may also be found. Dermoids are likely to present as midline masses (as opposed to epidermoids) due to the earlier inclusion of ectoderm into the neural tube. They usually appear at the suprasellar, parasellar and frontobasal region, in the posterior fossa or the 4th ventricle. The slow growth rate of dermoids delays the clinical presentation until the 3rd or 4th decade of life. The clinical presentation is variable and nonspecific. Headache, seizures and dementia have been described. CT findings of dermoid tumors include a hypodense mass in the range of attenuation values for true fat. These attenuation values are due to lipid material that accumulates from the sebaceous and apocrine sweat glands and due to cholesterol from the breakdown of squamous epithelium. The fibrous capsule may show variable enhancement. MR findings of dermoid tumors include heterogeneous mass usually at the midline. Sometimes fluid- fluid levels are observed. The lesion appears hyperintense on T1WI while the calcified areas are hypointense. On a fat suppressed T1WI the mass loses signal. On T2WI the fat containing areas are hypointense. When rupture occurs the fatty contents spread to the subarachnoid spaces. This results in acute chemical meningitis, seizures or transient ischemia due to vasospasm. Chronic sequalae include granulomatous changes and arachnoiditis. Hydrocephalus may develop due to granuloma in the aqueduct. CT and MR findings of ruptured dermoids include subarachnoid and intraventricular fatty deposits. These deposits may be mobile by changing the position of the patient’s head. Sulcal widening by fat is a pathognomic sign of ruptured dermoid.